CNCCookbook: Be a Better CNC'er

Do you want to be a better CNC'er in 37 Seconds?

Get Better Tool Life, Surface Finish, and Material Removal Rates Fast.

It's that easy. You can install and get results now.

January Through March 2007 CNC Blog Archive

 

3/28/07

Diagnosing and Curing Noise Problems in CNC Machinery

After backlash, the second biggest source of frustration seems to be noise problems on homebrew CNC systems. I added a new Cookbook page aimed specifically at gathering up the wisdom I've found for dealing with noise problems.

Quit Drilling With Your Tailstock in the Lathe

Widgitmaster made up these nifty drill holders that will fit in a QCTP holder:

He's got one with a chuck in it too. These just slide into a regular QCTP toolholder which is then clamped down on it. I've seen some chucks built into the full dovetail toolholder. One nice thing about this approach is you can set the cutting depth relative to the QCTP by sliding this holder and locking it down at the right spot. This would allow a series of tools to be aligned to the same depth and a carriage stop used to make repeatable production with a set of tools easy.

One thing about using the QCTP to hold these is you will have to dial them into the center of the workpiece. Widgit claims this is a more accurate way to drill holes on the lathe assume you do dial everything in. The fast way to get one dialed in is to place a precision pin in your lathe chuck and then clamp the hole or drill chuck from your holder onto it. You can adjust until it's centered just right.

I'm going to be making some drill and chuck holders for my gang tooling plate after I get it made. I probably won't make any QCTP style like these though. The gang tool plate uses much simpler holders that are square throughout and have no dovetails.

3/28/07

Handy Pre-Ground Parting Off Tools from eBay

Somehow I forgot to mention I'd found these really handy parting off tools on eBay:

Read my mini-review of them on the parting off page. The short story is I love 'em!

3/27/07

Making a Timing Pulley

Saw this approach to creating a timing pulley by drilling holes and thought it was clever:

Still needs a deburr and polish to finish off, but looks like a workable way to making one of these pulleys.

3/25/07

Ballscrew AC Bearing Blocks

Using double angular contact bearings to hold at least one end of your ballscrews (the other is often "floating", either free or in a simpler bearing) is key to minimizing backlash. If the ballscrew itself can wiggle axially in the bearings, that translates to backlash. Some guys on CNCZone tracked down a bearing block from Misumi USA that looks pretty good for $70. These are called "BRW". These seem like a deal at 1/3 the cost of equivalent THK blocks. They use ABEC5 bearings, which is 1 step down from ABEC7.

That gives you some idea of what it costs to buy commercial bearing blocks if you don't want to have to make your own. At that price, these are not going to be ultimate high performance. That's less than the cost of a decent set of ABEC7 AC bearings like a VMC would use, but they might be just fine for most hobby machines.

3/24/07

EZClamps

You recall the EZClamps? I was waiting on some endmills to arrive to try them. I got bored this weekend and couldn't wait any longer, so I used a 1/16" endmill instead of a 1/8". This is the second thing I tackled with the mini-router. I didn't know if it would cut aluminum or not, but it seems to do just fine. I wanted some clamps to make it easy to hold stuff on the table, so I whipped up this design in Rhino 3D:

I loaded a 1/16" ball mill into the Dremel and had at it:

I didn't let it finish, because it would have taken several hours. Feedrate was 9 ipm, but had to be slowed to 5 ipm at the very beginning of each depth pass. Like the turtle, I used OneCNC to generate the G-codes. to hold the aluminum block I just superglued it to a piece of poly board which was then held to the router table with T-nuts. Very cool!

The finish is actually a bit nicer than it looks in the picture. I'm sure there's a lot that could be done through experimentation to improve finish and speed up the overall operation of it. Click here to download a short video clip of the router cutting the aluminum.

Model Turbines

Model jet turbines have to be the ultimate machining project. They run at 100K rpms, so tolerances have to be just about perfect or they self-destruct instantly. Here is a gorgeous example on a cool thrust measurement sled:

Built from plans by Heward Microjets...

Commercial manufacturers building these engines for hobbyists are getting $2500-$5000 apiece for them.

Twin Lockwood pulsejets: Wow!

If you like this sort of thing, there is a Yahoo Homebuilt Turbines Group as well as the Gas Turbine Builders Association. There are some good CNCZone threads too. Another one.

Clever Lathe Slotting Attachment

A lathe slotting attachment is on my ToDo Wish List, so I perked up when I saw this in the Wankel Engine thread below. To make the Wankel requires broaching a gear into the inside diameter of the rotor: no easy task! This fellow resolved that problem by creating a slotting attachment that moves the existing compound slide on its dovetails (clever!) and that uses a faceplate with holes around the periphery as a dviding head to index to each tooth position. Quite ingenious!

Slotter bolts a bracket in place of the bracket that normally holds the compound leadscrew...

Another view. The indexer for the "dividing head" is bolted where the follower rest would normally go...

Just Try Making a Wankel Engine Without CNC!

There is a great thread on CNCZone about a fellow that's trying to make a Wankel engine. I say trying, because I don't think he ever got it to work well due to issues with the end seals and compression of the motor. Still, there are some pretty nice pictures of what he accomplished:

These are just a test...

All done on a 2D only (Z-axis not CNC'd) little mill. Looks similar in capacity to my CNC Mini-Router!

Grinding attachment actually includes a small spindle that fits inside the mill's existing spindle. That's a clever idea!

The real thing, with ground finish in combustion chamber...

Gorgeous piece of work, no?

Aluminum Side Covers with Bearing Pockets...

The eccentric shaft for the Wankel...

Rotor with Internally Broached Gear (Lathe Slotting Attachment)...

Complete except for front cover...

Done! Nice form factor for an R/C plane...

Tubing Straightener

I came across this one randomly while searching for something else on the HSM boards. I don't know that I would ever need such a thing, but it is really nicely made (as are all of McGyver's projects!):

3/23/07

Ordered Some Metal Today!

Just to be sure I keep more irons in the fire than I can handle, I ordered some metal from Speedy Metals today. I sent for a chunk of 11/4" thick cast iron plate to use in my gang tooling project for the CNC lathe. In addition, I ordered a couple of pieces of 1/4" thich aluminum 6061. I intend to use these as carriers to mount components to as I build the electronics enclosure for my IH CNC Mill conversion. Woohoo! Lots to do!

Real Machinists Can Fix Machines

Over time, I have come to the conclusion that real machinists are used to the idea that they have to occassionally fix one of their machines, sometimes even when its new or when others might think it is unacceptible that there is a problem. The real experts seem to just take it in stride and get one with fixing the machine so it can be productive for them again.

At the hobby end of the spectrum, one often reads a lot of belly aching about one thing or another on hobby machine tools. Most of them are Asian, and there are going to be some quality control problems. Many times the machines and accessories are more kits than finished products. The hobbyist looks at this, throws up his hands, and starts to complain bitterly about quality and how they were sold a bill of goods.

I've heard no end of complaints that the "professional" range 12x36 and up Asian lathes can be almost unacceptible in quality unless you buy a Taiwan lathe. One guy goes to great pains to point out every little detail problem with his new Jet 14x40 lathe. I read his article, and he did a fine job polishing up the lathe, but I found absolutely nothing there that would have stopped a good machinist from making good parts with that lathe as it arrived out of the box. The venerable Widgitmaster whom you've heard me speak of many times owns a Birmingham YCL lathe and has nothing but good things to say about it, yet this is one of the more maligned (outside of Harbor Freight and Enco) lathes I've read about!

Let me tell you that after reading thousands and thousands of threads on various boards over the years, I have seen problems no matter which way you turn:

- Want a great piece of Ye Olde American Iron like a Bridgeport? Converting it to CNC? I'll send you a list of stories where this went badly wrong. Everything from worn out ways, bad new new expensive ballscrews, bad spindles, you name it.

- Bought a new VMC? Yeah, happens there too. Comes up on the PM boards all the time. Guys buy expensive machines that show up with problems or develop problems not long thereafter. I don't care what brand you pick, someone has a lemon story to tell you about it. One of the guys that was really vociferous about his IH problems to the point he got kicked off CNCZone still hasn't bought another mill as far as I can see. He wanted a Hurco but had a big fight with the dealer over there.

- Used VMC? Same stories. "It looked great at the dealer, I saw it run under power, I got it home and it is a total disaster." Yada, yada, yada.

- Tormach? There's a big blowup over on their Yahoo board as various owners are discovering that their column, which is pinned at the factory, is out of tram by various amounts. Many of them never checked it but started finding mysterious errors in their work.

Heck, if nothing else you're eventually likely to crash and break the machine anyway, or wear something out that will need a tune up.

Over time I have concluded that part of calling yourself a machinist is being able to diagnose, fix, and work on these machines. Having the ability to do the detective work needed to track down and fix an issue is what really separates the good ones from the also rans. The guys that are happily posting about how they diagnosed and took care of some problem or other always seem to be the same guys doing awesome work in their shops. The guys complaining that the paint doesn't look right on their new Asian lathes? Well, they may be great machinists, or they may just be guys who ought to be painting lathes.

3/22/07

Universal Indicator Clamp

This came up on eBay and looked like a better mousetrap. Works with either the pin type indicator mounting or the dovetails:

3/21/07

4-Axis Mill Beats Lathe on Round Bars?!??

I never would have guessed it, but Geof on CNCZone says the following 4-axis mill set up was able to machine these aluminum bars to length, ensure the faces were square, and drill and tap a hole faster than he could do it in a lathe:

Hmmm. I'm guessing the reason for that is that he has to deal with both ends. A basic lathe will do one end great with a bar puller, but then you have to reload each piece by hand to get the other end. This setup gets 8 of them done per setup, which saves a lot of manual intervention. I believe their are lathes with more than one spindle that are designed to deal with the problem by transferring the part to the second spindle. Nevertheless, this is a very cool idea for saving time!

Widgitmaster Gives an Excuse for Another Purchase

One of the problems a new machinist faces is understanding the variety of products that are similar, but slightly different. This raises the question of whether you need both varieties, when is one better than the other, and so forth. In some cases, it is kind of a brand issue. Interapid indicators currently have the best reputation if you want a super high quality test indicator, especially one that measures tenths. I keep a Tool Brands page with notes I jot down any time I hear something like this about a brand.

In other cases, there is some subtle difference in the two that isn't obvious at first glance, but that makes more sense later. Let's consider angle blocks, which is the subject of this current rant. I bought a couple of precision angle blocks so I'd have them on hand for setups. My two are similar to the two in the back row of this picture:

They're got that "precision" look that a ground finish and lots of drilled holes gives, which is instinctively attractive to the average machinist like myself. There are variations on these, of course:

I would have been tempted to think this might add useful variety to my angle block collection by giving me a larger block (it's about 6" wide) and adding those nice reinforcing webs. We've got a few holes, which look handy for clamping, and though we've lost the nice ground finish, maybe that's okay for some jobs. Probably the last angle blocks I would've considered are these ugly cast iron types that have a "handle":

Heck, there's no holes in these at all, and there's just one web in the middle. Why would I want one of these? Along comes the Widgitmaster with another intriguing setup. He's got to drill a longitudinal hole through a big tall plate of cast iron. How does he set that up? With my least favorite angle block of course:

The angle block is sitting in the Kurt vise, and the workpiece is clamped to it with a Kant-Twist clamp. BTW, I love Kant-Twist clamps and won't touch anything else if I have a Kant-Twist that is the right size. You can see that having the web/handle in the middle made room for the Kant-Twist. I'd have thought a second one on the left would make sense, but maybe Widgit didn't have one. The plate sits firmly on the mill table and is true against the angle block and table. This would be an awkward thing to set up very many other ways. I would probably have tried to stand it up in the vise or just clamp it to one of the other angle block styles sitting on the table. Here we get good support up where the action is, which has to be a good idea.

Apparently this type of angle block is more properly referred to as a "knee block". You learn something new every day.

Thanks Widgitmaster, something else to add to my acquisition list so it'll be there if I ever need it!

3/20/07

An Epoxy-Granite to Stiffen an Existing RF45 Mill

This morning I awoke to find a nice couple of posts in the CNCZone Polymer Concrete thread about a fellow who is using EG to stiffen the base and lower column of his existing RF45 (similar to my IH mill) mill. He's using West Marine 105 epoxy, West 206 slow hardener, and a mixture of river rock and sand as the aggregate. He fabricated a welded steel partition from 1/4" plate to manage where the epoxy is going:

Partitioning system is secured by bolts at the front and rear of the base...

Before pouring the epoxy, he also plumbed in a one shot oiling system. Here is the first pour he did to get started:

First EG pour in the base...

davo727 plans to pour his base, and the lower part of his column for this project. In addition, he has fabricated a much more solid assembly to bolt the column to the base:

3/4" Plate Bars Add Beef Below for the Column Bolts...

Column Backing Plates are Also Secured From Above...

The column support system is also being augmented by a central large diameter bolt that goes from the base all the way up to the top of the epoxy fill in the column. Steel plate above the epoxy and below in the base provide a solid sandwich for the bolt to latch on to. It occurs to me it may be pretty hard to tram in the column with that arrangement as the central bolt will be capable of considerable compression force. As in many things, a little care and time spent should get it done.

Here is the finished result, which added circa 65 lbs to the 100 lb base:

That came out looking very professional!

This will be quite interesting to watch and hear reports on how successful it has been. It's not really all that much work to do this kind of thing, so if there is a profound benefit it could well be worth it.

3/19/07

An Epoxy-Granite Milling Machine Design Sketch

This design exercise was inspired by the Polymer Concrete thread on CNCZone. PC is a technique of using epoxy resin with an aggregate added to it to create a material that is not as strong as a traditional machine frame, but that has excellent dampening qualities. There is more than one kind of Polymer Concrete, but one using Epoxy Resin and Granite Aggregate for filler seems to be quite good for these applications.

In any event, I have sketched a table for a gantry-style mill and filled in my thoughts on how to go about building such a thing. As mentioned, this is just a design sketch, but it seems to me it has quite a lot of potential as a way to construct high precision machine tool components without a fancy shop. Here is an image of the finished table:

An Epoxy Granite Table for a Gantry-style Milling Machine...

3/17/07

More of the Fidgiting Widgitmaster's Machine Work Wisdom

Whenever the Widgitmaster, a long time CNCZone contributor, has something to say, I'm all ears. I have learned so much from this guy because he takes the time to document his work step by step and he is a professional machinist with many years of experience. The work he produces is gorgeous, and I love the CNC Mini-Router I bought from him.

His latest project involves converting a turret he found on eBay to work on his Birmingham lathe. A turret is a device used in manual work that is similar to toolchangers for CNC. In fact, I suspect one would make an excellent starting point to building a CNC toolchanger. They look like this:

 

The turret is mocked up on his lathe with a slab of cast iron he is machining to hold it...

The turret is designed to rotate to bring each toolholder into position. The toolholders are held via the 8 T-slots you see machined into the turret. A QCTP is very nice, but imagine being able to bring 8 tools into position just by unlocking the turret, swiveling the right tool into place, and relocking? Widgitmaster is going to be turning out Widgits faster than ever before!

I'm not here to steal the Figiting Widgitmaster's thunder on this project, so you should go visit his thread if you want to learn more about turrets. However, I do want to point out some cool things I've learned reading the thread, and that's what follows with the entries below.

Widgitmaster Marks his Cross Slide Travel

Let's start with that last picture of the turret. Check out the travel marks on the cross slide. Clever idea! I don't know how often I would use them, but it might be real handy to see that you're about to run out of travel soon before it actually happens! It is certainly easy enough to do:

Just 3 little marks and you know your limits!

Widgitmaster Machines All Surfaces Flat and Square First!

I've mentioned this before, but I always feel it is worth repeating. One of the first things I learned from the Widgitmaster is the need to start out with all surfaces flat and square. This has been crucial for me on many projects such as my Kurt Vise Stop, and whenever I've missed this step it has resulted in problems later on. I've read that many shops keep their old manual mills busy just squaring blocks to feed the CNC machines.

 

Widgitmaster Builds Setups for Rigidity

Every owner of an Asian machine tool complains about lack of rigidity compared to Ye Olde American Iron. Every owner who buys a bigger tool says the smaller tool really lacked rigidity and the difference was immediately obvious with the new tool. But in how many cases is the limiting factor something to do with how the machine was being used? I notice the Widgitmaster goes out of his way to add rigidity in his setups. Most HSM's just throw stuff in the vise and tighten it down hard and assume that's good enough. Let's look at some of Widgitmaster's tricks on this turret project.

1-2-3 blocks add a lot of rigidity to this setup. I kind of wonder why he didn't drag out the 2-4-6's though! Note the jacks under the ends. This may be about rigidity and it may also be about not having the block of cast iron slip downward in the vise. Either way it looks like a good idea! He left 0.010" for finishing after running the 3" face mill. He'll use an end mill to do the finishing job as it will leave a nicer finish than the face mill...

Now he wants to set up 4 jacks under the 4 corners of the cast iron block. He makes sure they're exactly level using this surface gage and DTI along the edge and the mill table as a surface plate. Those 4 jacks are going to lend some beefy support!

I had to throw this one in gratuitously to illustrate the use of a planer gage. Widgit is using a planer gage to measure this distance. He can take a micrometer to the planer gage to see what the value was. I've also seen planer gages set to a particular distance and then used to set something up on that distance. I need to put one of these on my tooling "Want List"! Stuck in the collet is a piece of .7500" hardened drill blank pin. That's probably also something that would be handy to keep around...

3/17/07

Rotating Ballnut

Every now and then I read about someone being interested in a ballscrew setup where the ballnut rotates instead of the screw. I thought of these queries when I came across pictures of a Bridgeport BOSS CNC mill's X-axis arrangement:

In the case of this Bridgie, it allowed them to position the drive mechanism where it is well protected under the table and the servo motor and drive remains stationary. Doesn't it seem like it also requires fewer parts (i.e. would be cheaper to manufacture) and is less likely to suffer from backlash? I say this because one simply needs to mount the ends of the ball screw so they can't move. An AC bearing arrangement would hold the ballnut axially. It also seems like a more rigid arrangement to have the ballscrew rigidly held at the ends. Lubrication might be a little trickier as you'd need to lube the screw not the nut.

Here is another example used a little differently:

3/16/07

Vector Drives vs Ordinary VFDs

VFDs or "Variable Frequency Drives" are great gadgets that go between the power source and a motor and allow the motor's speed to be continuously varied. They do this by means of something called "Pulse Width Modulation" where they are essentially varying the frequency of the current going to the motor. Thing of the frequency as governing how many "pushes" the motor gets. 60 Hz or 60 cycles per second is normal. A typical Hitachi 3HP VFD can deliver 0.5 to 360 Hz, which is quite a speed range!

Enter a new and better gadget, which has the really sexy name "Vector Drive." A white paper by Reliance Electric gives the full details, but in a nutshell, these drives are called vector drives because they understand the vector relationship between magnetizing current and torque producing current and they do the right thing with that.

What does doing the "right thing" buy us? Well, several things are better for vector drives than plain old VFD's:

What's the downside? Largely cost. An equivalent vector drive probably costs 20 to 30% more than a VFD of the same horsepower capacity and it will require you to install a tachometer input to give it feedback on what the spindle is doing.

Belleville Washers and Retention Studs: How the Other Half Does Drawbars

Most small mill and knee mill owners are used to R8 tooling which uses a thread drawbar to pull the holder up into the taper as the threads are tightened. Modern CNC mills use retention knobs and tension generated by Belleville washers to apply 1800 to 2500 lbs of force to pull the holder up into the taper. An air operated cylinder pushes down on the drawbar to compress the springs and allow removal. The whole assembly looks about like this on a Haas machine:

The retention ball or pull stud is held by a set of ball bearings. When the compression on the drawbar is released, the whole assembly moves up and a tapered bore causes the ball bearings to grip the stud tightly. Nifty, eh?

3/15/07

Dust Guard for the Widgitmaster Mini-Router

This is just a little sketch I did for the Widgitmaster who is worried about the impact of dust and contamination on his mini-routers:

Cool Shopbuit Rotary Air Indexer

No sooner had I written my notes below about Face Gear Rotary Tables than I found out about another fellow's rotary air indexer project over on CNCZone. ServoWizard is a 40 year veteran machinist and it looks like a bit of an inventor too. He built this indexer to make pulleys for high performance go karts:

They're really nice made, complex CNC parts. The number of teeth are engraved on the side of each pulley, a nice touch! He's using a CNC converted Bridgeport with a controller and software he wrote as his first programming project. Here is the air indexer itself:

Air indexer...

The indexer uses two air cylinders and an electric solenoid valve for control. A larger air cylinder locks the pin into the indexing wheel. The smaller cylinder, visible below, actuates a sprag clutch to advance the wheel to the next positon. Sprag clutches are gizmos that look a bit like a roller bearing that have low friction in one direction of rotation and high friction in another. This gives the air cylinder a ratcheting ability to turn the indexer. An adjustable travel slide allows the stroke length to be setup for different index wheels so that the right index slot is positioned:

What a nice piece of work, eh? Just remember Gene Haas got his start building rotary index tables, not mills!

3/11/07

Tramming Tricks

I stumbled across a thread on PM talking about how to make a tramming bar and saw a couple of clever ideas.

The first idea talks about how to tram based on how the mill cuts:

Take your test block, (you do have a test block? a chunk of Al, 2X2X6 or 1.5X1.5X8 or whatever). Slap it in your vise, smack it down good on some parallels, snug it up and take a test cut along the X, fly cutter or a face mill, something that will cut the whole surface of your dedicated test block. Just take a skim.

Pull out the indicator, with holder of your choice and sweep the cut you just made, unless you are superman, and I think I was once, you will have a concave cut. Tram the head so that the low points on the concavity are level. This will get you pretty close, take another cut, and dial it in even further.

What this accomplishes, is that you are not squaring your head to the table or to the vise, but to the actual travel of the table, which is the important thing. Grab the test block along the Y axis, and get the tilt of your head correct.

Now, you can use that test block for all kinds of cool tests to find out what your mill is doing. How level your vise is to the travel, by flipping the block. You can find out what kind of droop and sway you have, what kind of twist, flattest place in the travel on your table. We had one mill that ran pretty flat and then dropped off one corner by about .0015.

I like that idea a lot, especially if you are using Asian machine tools of unknown trueness like I am. I wouldn't say it's something to do every time you tram the mill, but doing it at least once to see how things are performing seems like a good idea.

The second idea concerns making special tram goodies that may have other purposes:

Special built tram bars can be artistic creations or personal challenges provided they are made for maximum flexibility in use. SIP made a dandy where the indicator slipped radially along a rail so it could dial in OD's and IDs plus tram in faces. It wasn't very ccmpact but it was very versitile.

I recently wondered why somone hasn't taken a scale and reader from a defunct digital caliper and installed it on a home-made tram bar. Once set it could be used to dial in a arc to determine the radius, find center between features etc. Gimmicks like this can spawn whole lines of handy manufactured machine tool accessories.

That last was from Forest Addy. Hmmm, he gets you thinking, doesn't he?

3/10/07

Great Ballscrew Bearing Block Diagram

Shows how a pair of AC bearings are mounted to secure one end of a ballscrew:

Nice Indicator Sweeper

Somewhere I came across Bottle Bob's site and saw this very nicely made copy of the SPI "Zero-It" indicator sweeper:

Very nicely made, eh?

He says he leaves it set up in a 40 taper holder and uses it more than any other indicator holder he owns.

Staking Ball Detents

How do you close the diameter of the hole slightly to hold a ball detent in place? The operation is called "staking" and can either be done with a special tool as pictured or with a big ball bearing:

You can also buy a ball detent that screws into the hole.

Cecil Walker's Spectacular 1/2 Scale Ma Deuce

Unbelievable toys:

Cecil's 1/2 Scale Ma Deuce. Working guts are Ruger 10/22. He even made the scale ammo can!

Gun was made from CCS Prints plans. They also offer Browing 1917 and 1919 based on Ruger 10/22...

Dually Pickup Hauls 2 Lathes

Kinda makes me want to trade my Suburban in on a dually pickup:

2 heavy Shaublin lathes and a load of tooling = circa 6000 lbs...

3/08/07

New Mini-Router Project: EZ Clamps

One thing I don't have yet for the mini-router is any kind of a clamping kit. Widgitmaster includes some T-Nuts with the router, but there are no clamps to go with them. I just used some bolts to do my first project, but something more convenient would be called for. Enter the EZ Clamp:

The EZ-Clamp...

I've seen this style of clamp before and thought they would be quite handy as they do not require step blocks. I'm not sure what they're really called, so I just named mine "EZ-clamps". This is the sort of thing that is ideal for me to do with CNC. It would be hard for me to machine them manually, yet it seems straightforward to do with CNC.

I intend to make them out of 1/2" aluminum. It will be interesting to see whether the mini-router is powerful enough to make them. I'll be using a 1/8" end mill to do the cutting. I plan to clamp the aluminum atop some poly cutting board and have at it using relatively gentle feeds and depth of cut. The g-code program is straightforward to create using OneCNC. All I need now is for my end mills to arrive in the mail: eBay purchase.

Fitting CNC into a Smaller Case

PC motherboard form factors seem to get smaller and smaller. How about the VIA EPIA motherboards? Here is the current highest performance model, with a clock speed of 1.5 GHz:

VIA EPIA EN15000G PC Motherboard...

The biggest issue is you've got LAN and USB, but no parallel port. That means running something other than the basic parallel breakout board with Mach 3, such as a GRex or ncPod. Still, this card is a mere 6.7" x 6.7". This form factor is known as "Mini-ITX".

Compare it to the Asus A8V-VM, which is a Micro-ATX form factor:

Asus A8V-VM Motherboard...

This one has that essential parallel port for Mach 3, and it is still tiny at 9.6" x 8". It's very similar to the A8V-MX I used to create my rack mounted CNC lathe PC.

It really would be interesting some day to see just how small an enclosure could be built to house a PC, suitable breakout controller, 3 or 4 Gecko drives, and power supplies for the PC and step motors. My guess is it could be made very small and probably would cost about $1000 in components.

Tracking Down a Parallel Printer Ribbon Cable

Speaking of small form factor PC's and my rack mounted CNC lathe PC, I had to go looking for a parallel printer ribbon cable. I need this to be able to run my Xylotex-based CNC mini-router off the same PC. The problem with the normal round parallel cables is they're too bulky for my tiny little case. I can't get the cable in and out without it running into the monitor support on the rack: Doh!

For the time being, I'm just running with the PC enclosure kicked forward out of the rack about 1". However, the ribbon cable style are much more compact and can fit into tighter spaces. It took me a fair bit of sniffing around, but I finally found some 4 foot cables at Jameco. These would be ideal for putting all of the components into one box I think. I used to buy a lot of electronics components from them years ago as they were one of the first surplus electronics outfits in Silicon Valley selling digital parts. It was fun to get reacquainted.

Along the way I found a site that shows how to make your own ribbon cables using crimp style connectors and a bench vise. It looks darned easy!

I would've made my own cables, but the parts added up to more than Jameco was charging and I have no idea when I'll need another one.

3/07/07

Manual Digitizing for Reverse Engineering

The venerable Widgitmaster has come through once again with a description of how he is reverse engineering a Hardinge Turret to fit his Asian lathe. He needs to make a custom mounting plate, and in order to do so, he wanted an accurate drawing of how the existing turret plate expects to be mounted. So, he clamped the base plate to an angle plate, set the result up on his granite surface plate, and started taking measurements with a height gage:

Taking measurements off the bottom of the turret...

By clamping to an angle plate, you can flip the item 90 degrees and develop a true set of X, Y coordinates for various features simply by measuring their heights. You'd have to clamp a little differently than Widget shows here, but you get the idea. Now taking that list of coordinates, the Widgitmaster was able to produce a drawing on graph paper:

Resultant drawing...

It would be super easy to take a list of coordinates and rapidly produce a Rhino 3D or other CAD drawing. I'll have to remember this the next time I am trying to reverse engineer something.

3/06/07

First CNC Chips Cut

This evening after work I was able to do the last little bit I needed to run my first CNC part program to completion and cut some real chips. Here's a nice picture or two of what the result was:

As you can see I cut a couple of Hawaiian Turtle Glyphs into a block of wood scrap using my Widgitmaster CNC mini-router. Full details are on the mini-router page, but I can tell you it was great fun to finally get there and run a program!

3/04/07

Etching Glass with CNC

Here's a nice piece of work:

So how do you etch glass with a CNC router? The trick is to use diamond burr bits ($6 a set at harbor freight) and cut in thousandths. Also it can't be tempered glass. Wow, that's something I'll have to try for myself sometime!

The Widgitmaster's Travelling CNC Medicine Show: Up and Running

I woke up this morning and couldn't stand the thought that the only thing stopping me from running the mini-router was a set of couplers for the step motors. So, I headed downstairs to the shop, fired up my lathe, and whipped up 3 couplers. They're just cylinders with a 1/4" ID hole and two 1/4-20 set screws. They seem to be working out great.

It took me a little bit of effort to get Mach 3 all calibrated and running properly, but the tutorial on setting up Mach worked out just fine. The next thing I did was to fire up my copy of OneCNC Mill Advantage XR2 and gen up some g-codes. I decided on a simple logo, the word "CNC" in 1" high letters. The engraving toolpath in OneCNC will just run the cutter around the outline of the letters. I had to fool with it a bit, the Mach 3 post that came out of the box with OneCNC wasn't right somehow (it threw off big arcs for some reason), so I downloaded the latest post and gave that a try. Sure enough, all was well. It takes about 750 lines of g-code to do that simple logo, but it was great fun watching the router cut air.

Now I need to cut the logo for real. The main thing holding me back is I don't have a computer in the shop yet, and I don't want to make a big mess in the office with the chips flying. I'll have to think on that a bit.

3/03/07

The Widgitmaster's Travelling CNC Medicine Show

There has been some progress on mounting the electronics in the toolbox. All I need now is a set of couplers and I can't mount the motors and the mini-router will be ready to start cutting! I also started a CNC Mini-Router page to chronicle the project in one place, and eventually to walk through some of the things I make with the mini-router.

Finished Electronics Tray...

Mounted in the Toolbox...

They Were Made for Each Other!

3/02/07

Drill Press Cam Lock Clamp

This is a handy gadget:

This does not look at all hard to make, but if you'd rather buy one, Travers Tool has the clamp, $77.32 each, part no. 61-171-001.

Hooks to the column, swings out of the way when not needed, and has a quick acting cam action.

LED Ring Light for the Mill

I love the magnetic base halogen lights I bought from eBay seller 800watt. I use them on my mill and lathe and they sure to help me to see what's going on with the work. I came across this unique light on the PM boards, and was impressed. I don't know when I'll get around to building one, but it seems to be well worth a look. Here are some photos:

Is that a UFO, or a milling machine?

Bunch O' White LED's...

Aluminum Ring Housing...

PC Board...

This fellow cannibalized a set of holiday lights he got for $12 to harvest the LED's. The PC Board wires 2 LED's in siries and then hooks each pair in parallel 22 times, for a total of 44 LEDs. The unit is powered by a 4.7v phone charger. Someone on the thread suggested that each pair of series LEDs ought to have a 1/8 watt 270 ohm surface mount resistor in series because in the current design, if an LED shorts out it could take a bunch of others with it.

Because the light surrounds the spindle at close range, you get a lot of illumination with minimal shadows, which seems ideal for mill work. Lights similar to this one are available on eBay for use with microscopes in the $60 to $90 range.

A Tale of 4 Taps, Some Polyboard, and the Mystery Steel!

One of the many (too many!) projects I've got running along is to make my Widgitmaster CNC mini-router operational. It's an incredibly cute little machine that just needs to have some step motors bolted up and connected through a parallel port to be operational. Towards that end, I decided to use a small Craftsman toolbox to hold the electronics:

I figure its about the same size as the mini-router, its cute, and I can throw a few accessories in the tray if I want to take the mini-router somewhere to show it off. I had also ordered the complete 3-axis kit from Xylotex, which has all the electronics and step motors needed to get going:

Xylotex complete 3-axis kit is simple and inexpensive...

Having decided to put the electronics into the toolbox, my next thought was to create some sort of a mounting plate on which to attach the power supply and the Xylotex board. My original thought was a piece of aluminum, but I happened to spy a half forgotten package sitting in a corner of my office that needed to be dragged down to the shop. Based on a write up on the Industrial Hobbies site called "Saving Your Table", I had ordered some cheap poly cutting boards off the Internet. I got like 6 boards for $24 or something. This material looked like a good thing to make my mounting plate out of, and it would be fun to work with a new material. I had never messed with plastics much save for some experiments with plexiglass associated with my old PC modding activities--pre-machineshop to be sure!

The polyboard worked out well. It mills beautifully, without melting onto the endmills. It drills and countersinks as well. I set the board up with holes drilled for power supply, Xylotex board, and 4 mounting standoffs. The latter I turned from some "mystery metal" that I thought was 12L14, but it became obvious it was something tougher once I got to working with it. Here is what the board wound up looking like before I mounted anything on it or cleaned it up. You can see the standoffs underneath:

Top of board. Stand-offs are mounted using countersunk 1/4-20 flathead cap screws. The little cutout at lower left is a handle cutout--this piece of poly was originally a kitchen cutting board!

Underside with standoffs...

The standoffs were just turned quickly on my lathe. I got them to approximately the same length, faced them, drilled them for a 1/4-20 tap, and the ran the parting off tool. That last step was my first hint they weren't 12L14 as they chattered something fierce!

Stand-off. The gunk is some tape adhesive. When I finish I will clean everything up with brake cleaner so you won't see that stuff...

This was my first experience with countersunk flat head cap screws, and I have to say, I like them better than the socket head cap screws I had been using for everything. I ordered several boxes of them with my last Enco order, so you'll see them cropping up more often in my projects. FWIW, when you countersink, you just need to countersink to a depth of 1/2 the diameter of the flat head. You can take my tip and use a spot drill to do the countersinking and combine the spotting and countersinking chores in one operation too.

Next it was time to tap the standoffs. I decided to try power tapping, which I had read about in various places. Basically, I stuck the tap in an Albrecht chuck on the mill, dialed in the slowest speed, made sure the quill could feed freely, and loosley feed it in. The first one worked pretty well, albeit taking several tries and backing off. The tap seemed to be having some difficulty cutting, but I assumed it was my inexperience at power tapping. I did not put together the chattering cutoffs with the difficult tapping to realize I had something other than 12L14 quite yet.

The second standoff was a write-off--the tap broke off before I was a quarter of the way into the hole. Doh! ?!@#$%!!! It was getting late, so I shut down the shop and went to bed. The next morning, as I was turning and parting a new stand off to try again with, it dawned on me that what I was cutting was something a lot tougher than 12L14. I decided to leave the power tapping aside and hand tap in the interest of moving through the project and because I wasn't too sure what I was dealing with.

I also took the opportunity to try some upgraded taps I had bought from Enco along with the flat head cap screws:

Left to right: 3 flute 45 degree spiral flute plug tap, thread forming plug tap, thread forming bottoming tap...

Having broken my Craftsman tap, it seemed as good a time as any to try out these new "professional" taps. Like me, I am sure you've read in many places that hardware store taps are junk and shouldn't be used. Perhaps you are also like me in thinking, "Yeah, but hardware store taps are what I've got and they've worked for me so far." In fairness, I did buy the new taps with a thought I would try them and see how much better they are. I just hand't gotten around to it until the mystery steel and broken tap forced my hand.

Since I was dealing with brand new (and somewhat expensive) taps, I decided not to try power tapping. Too much experimentation can be a bad thing for progress. So I had 3 spacers to thread, and 3 new taps to try. I stuck each spacer into my Kurt vise and locked it down against a V-block and then went at it.

I first tried the bottoming thread forming tap. These are usually recommended for aluminum and mild steel, but I thought it worth a try here too from a learning standpoint if nothing else. I found it pretty tough going, but manageable. I used Tap Magic with all 3 of these taps.

Next I tried the thread forming plug tap. It was easier, but still took a fair amount of effort. Evidently the tapered end gives things an easier start compared to the bottoming tap.

Lastly, I fired up the spiral point tap. It's a Cleveland 45 degree spiral flute tap. This was the hands down winner by far! Turning effort was the lowest I've ever felt while tapping. Control was excellent. The 3 flutes sent up some wicked steel splinters out the top of hole, so you'd want to be careful around those. All in all, I was amazed at how much better this tap worked than anything I have used in the past. Cost from Enco was $8.86. You can bet I'll be on the lookout for more of these and will want to eventually round up a full set. I wanted to try power tapping these because it was so easy to do by hand, but I had finished all the spacers, so that must wait for another day.

 

Building a Manufacturing Business from the Ground Up

I'm always fascinated to read the stories of folks who start from nothing, often in their garages, and manage to build up an interesting manufacturing business. Recently, I came across this fellow, who frequents the boards as "2kjettaguy" and has a business called "42DraftDesigns" that makes aftermarket accessories for Volkswagens and Audis. I own an Audi TT that many of their products would work with, cool!

At this stage, his 2500 sq ft shop includes welding, 2 Sharp 2412 VMC's, a Jet 14-40 lathe, an injection molder, and it looks like a knee mill of some kind. There is a staff of 6 running the machines. Here is a view of it:

One of the two Sharps is running 2 vises, and the other runs a fixturing plate made of 1" 6061. He has a number of fixtures that drop down on the plate to facilitate manufacturing his products. He uses a CAM program his father (who is a programmer) developed. Look how clean everything is, just like the other pro shops you see. In some cases the VMC's are used to manufacture, in others, they are used to prototype. For example, he makes high performance exhaust parts, and will prototype the flanges, weld up his test pieces, and if he likes the result, the flanges are then farmed out to a laser cutter. He still welds the assemblies in house, however.

He started first with a little MaxNC mill and then moved to a Bridgeport Series 1 CNC with retrofit controls he installed:

And here is a piece he did that I thought was cool. It is for a friend, not his company:

Looks like quite a step up from humble beginnings, no?

Custom Aluminum Extrusions

I came across this while researching the write up on 42DraftDesigns and found it interesting. He needed some custom extrusions for a speed part he wants to manufacture that look like this:

Looks like an intake runner or something?

In any event, a firm called Minalex quoted $1100 for a custom die and then $4.63/lb for the finished extrusions up to 100 feet. That gives a ballpart for what custom aluminum extrusions cost.

How Many Machines Per Employee?

How many machines can 1 employee keep running in a commercial machine shop? The answer is, it varies, but should be at least 2 and maybe as many as 4 or 5.

Keys to Machine Productivity

The answer for small shops, especially one man operations, was summed up in a PM post as, "buy as much spindle as you can afford and a toolchanger.

This makes sense, as changing tools is a mindless task that shop with few employees ought not to be engaging in. In real world terms, a VMC ought to be at least 4x faster than a CNC'd knee mill. That's why there's so many used knee mills out there for $10,000 or less even though they still have life left in them.

It seems to me that this toolchange overhead problem is much worse on lathe work. I find I am changing tools on the lathe much more often than on the mill. I can get a lot done with one endmill until I need to start drilling or something. This has gotten me interested in gang tooling for lathes, which looks to me like the easy way to solve that problem. Omni-turn's catalog provides a lot of great pictures and ideas around gang tooling lathes.

Coming up with a cheap and easy toolchanger for the mill promises to be more challenging!

Another good suggestion from that same thread is to do a different setup on each vise on the table. Why? Because it will uncover any problem sooner before you've run all the parts through the bad setup or program.

2/28/07

Bearing Preload to Reduce Backlash

Ballscrew mounting bearing blocks commonly employ preloaded angular contact bearings to reduce backlash. They securely hold the leadscrew (a ballscrew in this case) so that it can't move in and out along its axis. Recently I read an account where someone greatly reduced the backlash associated with the ACME leadscrews in their mill by forcing a little preload in the mounting bearings. The collars that hold the leadscrew were simply pinned to the leadscrew shaft. He found that by removing the pins and placing a bolt in the end of the shaft with a pressure washer, one could dial in preload to reduce the backlash. In his case, he reduced it from 0.012" to 0.0025", which is actually pretty darned good for an ACME leadscrew on an Asian mill.

Now the downside is that the bearings these mills use are not angular contact bearings and aren't really designed to take a lot of preload. Too much force can ruin them completely, so go easy on them. Even modest forces will likely shorten their life, so you may want to use the newfound precision to machine a custom bearing block capable of holding some real angular contact bearings.

I am always inspired when I read that someone went into the guts of their machine and improved it with a simple fix like this. My reaction is always that here is a person who really knows how to think about machinery and understand what's really going on. Most of us would take the darned thing apart, fail to find anything that looked amiss, bolt it back together and give up on improving it. A real machinist or engineer is methodical and has an intuition about these things.

Royal Taper Attachment

Cutting tapers is seemingly a daunting process on a manual lathe and a non-event for the CNC crowd. For this reason, there are a number of purpose-builtattachments for manual lathes to make the job easier. Typically they involve a device mounted on the back of the lathe that involves setting a bar at the proper taper angle and then using that bar as a rail to move the cross slide at the same angle. Such devices are available commercially (for $700 or more) or they can be readily constructed in the shop.

An alternate approach involves attachments for the tailstock that place the center, ummm, off center. Recall that the pain of setting the tailstock over and then getting it back into proper alignment is one reason people want the attachments. It is therefore ironic that one can use an attachment to accomplish the same setover. Traditionally I have seen these done by adapting a boring head to fit the tailstock. This is a pretty easy approach as the boring head will already have a nice dovetail and adjustment screw.

Recently, I came across this photo of such an attachment that used to be available from Royal:

Royal Tailstock Taper Attachment...

I thought this was a very nicely made little gadget that might make a good model if one wanted to build such a thing. There are several interesting features to note. First, take note that the live center actually has a little ball on the end, not a point. There is a discussion of why the ball is necessary in the PM article I linked above, so take a look if you are curious. Second, there is an integrated level, because of course it matters how the offset is achieved. Lastly is a micrometer dial to perform the fine adjustment together with a scale on top that shows the grosser degree of the adjustment. Again, this is very nicely done.

Unfortunately, like so much else from the manual machining world, these gadgets are no longer being made as there is no longer enough demand for them.

2/27/07

The Lathe Parting Off Tool Can Be Fixed on a CNC Machine

This hadn't occurred to me until I was looking at a gang tooled lathe and noticed they offer this option. With CNC, you can arrange your programming relative to where you will part off, and this allows the parting off tool to be in a fixed location. Given the desireability of mounting the tool upside down and behind the workpiece for smaller lathes, it makes even more sense. This particular commercial machine has it as a $3000 option, which seems a bit much. All that is required is an attachment to the lathe bed in a fixed location with a stepper motor and leadscrew that will feed the cutoff tool into the work. Ideally you want to approach from an angle 90 degrees off the plane of the gang tooling so as not to get in the way of that tooling. From that perspective, it might make the most sense to have the parting tool descend from above.

I don't know what I will ever do practically with this idea, but it was interesting to come across. I think I would mount a tool setting sensor to this attachment if I were to create one. In practice, one would write the g-codes so they're referenced entirely against the parting off position, which would be very near the chuck jaws. One could write the g-code program to position a stop mounted on the gang plate to allow the workpiece in the chuck to be properly positioned before the chuck is tightened down. Hit the button to proceed and your workpiece would be properly indexed relative to its length and chuck position, the tool would then touch off the sensor on the parting off attachment, and off you would go. If one insisted on mounting the attachment in the same plane as the gang tooling, perhaps it can be behind the chuck so as to be to the left of the gang tooling and in a place where that tooling likely wouldn't go too often. Or perhaps the retract travel would be enough to get it out of the way.

The attachment in the link I have provided is mounted to the headstock, for whatever that is worth.

More Gang Tool Tricks

Gang tooling is just a way of using an extended lathe slide to hold a lot of tools. The gang tooling assumes no tailstock, and so moves to the right before positioning a new tool so that all of the tools clear the workpiece. Once the new tool is positioned, the gang tooling moves back in to bring the tool to bear. It's a very simple way to get the benefits of a toolchanger for a few tools without needing a lot of expensive mechanical gadgetry. Omni-turn's catalog provides a lot of great pictures and ideas around gang tooling lathes. Here are just a few things I learned:

Tailstock Sensitive Feed Attachment

If you use your lathe tailstock with a drill chuck very often you will appreciate this sensitive feed attachement:

It's very nicely made, isn't it? One thing I might look to add is a digital caliper that shows depth. There shuold be a way to rig that up. In addition, this attachment only has 1/2" of travel, and more would be nice.

2/24/07

Cutting Small Gears

Someday I will need to cut a bunch of gears for my Antikythera Astronomical Clock. Here are some pictures of gears cut for a scale model of a V-Twin motor:

Shaft is in rotary table and tail stock. The little digital controller is nifty!

There is the involute cutter...

Teeth are cut, now gears must be cut to size and final machining done...

Here they all are after boring and parting. Note the dime nearby for scale!

Being Slightly Less Egyptian: Machinery Dollies

I've had my eye on building some machinery dollies for some time. Since I want to purchase some machinery, the time has come to move ahead on these. I purchased a set of casters, and will shortly go pick up a load of square tubing to build this:

Its sort of a cross between a two wheel dolly and a toe jack. That blue cylinder in the middle represents a bottle jack. One would sidle one of these dollies up to either side of a machine or crate, connect the two together with load straps and perhaps some more tubing, give a couple of pumps on the jacks, and voila, the machine or crate has sprouted wheels. You gingerly roll it off to its new position and then release the jacks, loosen the load straps, pull the dollies out on either side, and you are done with the move.

Before I get too carried away with this I want to post the concept on a bulletin board or two and solicit some feedback. Rigging heavy loads is inherently very dangerous and I confess to knowing far too little about it.

 

2/18/07

CNC Rifle Stock

Actually, just some Rhino 3D doodles. A friend wants to get some Mauser actions and make some rifles. Naturally, I'd like to do the stock using CNC and a router. Here is what I came up with:

It's not quite right, but it isn't bad for a first attempt. I think it could probably be tweaked into decent shape with some more work.

 

2/17/07

Widgitmaster Finds His Limits

Sorry for the long hiatus on the blog, but I've been travelling on business. I came back to hear that the Fidgeting Widgitmaster, whom I've written about often in the past, is selling his very first CNC router that he built. It's a beauty! He published a link to his build log photos, and I happened across a really neat idea for integrating limit switches and protecting them from debris:

Integrated limits on the gantry axis...

The design is not unlike the optical limits available from places like Industrial Hobbies, but is based on a mechanical microswitch. It's really elegant. Looks like a little bearing on the end of the arm to keep things rolling smoothly, a couple return springs, and I can't quite make out what trips the limit, but presumably it will trip in either direction, so there must be a couple of protrusions on either side of the microswitch. Inside this cavity everything is protected from dust and other contamination. The ballscrew even has some sort of wiper arrangement. Read through the rest of the build log, this machine is a real work of art. Shows you how a pro approaches machine design!

Sieg Factory Tour

I came across this photo essay of a tour of the Sieg machine tool factory in China by the Littlemachineshop.com. This sort of thing is always interesting. One interesting thing was how much actual inspection was going on. I think we sometimes feel the Asian machines are assembled and shipped without any quality control, but these pictures would indicate otherwise. The second thing to note is that its nearly all manual. They own a single CNC vertical machining center--no mention of what it is used for. My guess would be making molds for the castings. The rest is done on manual machines, including machines we consider antiquated such as scrapers. Here is a surface grinder being used to grind the dovetails for a mill bed:

Scissor Knurlers

I'm adding scissor knurlers to my list of todos. I'm still using the old style, but they're not the greatest. There is a thread about these over on HSM as we speak with a couple of designs. One is very elegant, and the other looks dead easy to build:

 

Lest we forget, there is also a nice write up on making a scissor knurler on the site of the very talented Japanese machinist Mr. Ishimura. His involves an integrated QCTP holder, which would be nice.

Key for Tramming a Vise on the Milling Machine

I liked this description from the HSM board of how to install a key on a the base of a milling machine vise so that it will always be in tram on the table:

If the vise does not already have a key slot in the base, install a tight fitting key in one of the table's T slots. Invert the vise and clamp it to this key. Mill a keyway in the base of the vise, usually through the slots for the hold down slots, that corresponds to the table slot. Install a key in this slot with socket head cap screws.

You might have to shim the fixed jaw for the ultimate in tram, but the vise will always be reinstalled in the same position.

Another thought, if you don't want to modify the vise, is to make a tramming fixture that you clamp in the vise jaws. Said fixture would mate with the T-slot precisely enough to ensure tram as the vise is being bolted down.

Mega Santec

This would make quite an interesting machine for the home shop:

It's a manual bed millthat looks to be very sturdy. I've never really liked knee mills of the Bridgeport persuasion as well as bed mills, though they are far more plentiful in the used and Asian clone markets. I thought this machine was an interesting alternative.

 

2/10/07

My CNC Lathe Enclosure Project is Out of Control!

I've been making steady progress, still not done, but there is more to look at. The rack is fabricated, save for drilling mounting holes for the driver electronics rack mount enclosure. You can see the swing arm on top, with keyboard tray and LCD touch panel. The lathe's control panel is just resting there, but it will ultimately have a holster there. You'll be able to grab it and drag it over close to the lathe as a pendant or operate it right where it sits.

Rol-A-Lift

A chap named Archie recently dropped me a line and turned me on to what looks a very useful piece of gear for moving heavy machines around the shop: the Rol-A-Lift:

I understand they're available for rental from various places. Seems like a better deal than toe jacks, although I could imagine machines with overhangs that you couldn't get this thing under properly. A pair of these with a lift strap between them, a couple of pumps on the jacks, and you are ready to move your machine. Pretty cool, eh?

2/06/07

Buy More Than You Need On Little Things

Most of the cost associated with little things is shipping and handling. Even if you go to the store, the cost of your effort to take time away from your shop and go to the hardware store to buy a bolt or a nut dwarfs the cost of the nut or bolt in most cases. For that reason, I always buy more than I need, and I organize my storage of these little bits so that maybe the next time there will be one on the shelf. Rushing to the store to buy a tap? Buy 2. Need a 1/4-20 socket head cap screw of a particular length? Buy 4 in that length and 4 more in the longer and shorter lengths. I've been doing this for quite some time, and it pays off handsomely when you find yourself able to do more in you shop without constantly running off to the hardware store or ordering on the Internet.

I'm trying to finish off the electronics enclosures for my CNC Lathe conversion, and needed strain reliefs for the power cord. I got 600 (!) of them on eBay for $1.99 + 10.99 shipping and handling. When they get here, I will never need to buy a strain relief again. Now I could've run over to Radio Shack, dinked around, possibly been routed from the closer store to the bigger store as happens, and had the darned thing tonight for an investment of about 1 hour's time. I'd rather just order it, it will get here, and I won't have to deal with acquiring them again.

I organize all these little goodies in multi-compartment plastic boxes which are then stored in a big storage rack I built:

Label the plastic parts organizers on the top and side. I've taken to keeping the taps and dies with the appropriate hardware box so its all right there when I start messing with 1/4-20 hardware.

Put All the Plastic Boxes and Bits Into the Storage Rack...

When I order from Enco and other suppliers, I try to avoid onesy twoseys. If I need one 1/2" endmill, I probably could use two or three, so I order two or three. This is especially helpful with Enco, where I always try to reach the $50 minimum to use their free shipping offer anyway.

Sometimes, I have gone on the hunt to jump start my collection. For example, large hardware assortments are available on eBay relatively cheaply. You can buy assortments of things like O-rings, key stock, and bronze bushings which are handy to have around. At Christmas and my birthday, I always put a DIY hardware assortment on my list. I give people a general description, like "1/4-20 hardware", and then tell them to go buy 2 packages of every size bolt they have, a set of nylock nuts, some regular nuts, some lock washers, and some regular washers. Throw in a plastic storage box for them, and you have a cheap gift that I am delighted to recieve.

Once you have a well-stocked small parts larder, you will find it is incredibly useful and increases your shop productivity!

4-Wheel Disc Brakes for CNC

I had an inspiration during my commute today. I was pondering conversion of a rotary table for use as a 4th axis on a CNC mill. The conversion is relatively straightforward and has been documented in a number of places. One thing that commercial units often have is a lock that clamps the axis when the rotation has completed before machining for greater rigidity. What occured to me is that one could adapt an automotive disc brake to this purpose. Why not machine the rotor to replace the table of the rotab and mount the caliper to allow the axis to be locked for machining?

Being able to lock the axis might be particular important in dealing with the inevitable backlash of a standard rotary table conversion.

2/05/07

Countersinking Flat Head Cap Screws

Reading about this task on CNCZone I learned of a handy shortcut. One fellow says, "Forget the countersink, just do it with your spot drill up front, then drill the hole, and you are done." "Brilliant!", says I. Rather than spot drill, drill, and then countersink, let's kill 2 birds with one stone. The one fly in the ointment is that the countersink spec for US flat head cap screws calls for an 82 degree countersink, whereas spot drills are 90 degrees. This immediately led me to produce the following little chart that lays it all out:

First we have the size of the bolt, followed by the expected diameter of the head according to a manufacturer on the web. We can apply a little bit of geometery and realize that for a 90 degree angle, the cone of the cap screw is the hypoteneuse of a right isosceles triangle and 1/2 the head diameter is therefore the depth. Now a little trig and we can figure the error between the 82 degree countersink and our 90 degree spot drill's countersinking. As you can see, it isn't miniscule, but I doubt it is the end of the world either.

Note that 82 degree spotting drills are also available, though in fewer sizes. They will be spot on with no error. As far as I can see on Enco, 82 degree and 90 degree spotting drills cost the same. You will have to buy a pretty good sized diameter spotting drill given that you need one at least equal to the head diameter of the flat head cap screw you end to spot and countersink with it. A 3/4" diameter spotting drill is only good for 5/16" and smaller screws. These spotting drills are not cheap, and cost about 2x what a countersink does, so you'd better be able to justify that with the time savings. I think I would learn to sharpen drill bits in short order if I was planning on doing very much of it.

I have ordered up some flat head cap screws from Enco (having needed them for another project anyway), but I can see I now need to order some spotting drills so I can experiment with this!

2/04/07

CNC Lathe Progress

I am focused on building the enclosures for the electronics at the moment. I'm creating a self-contained rack that will have one enclosure for the PC, and another for the GRex, DC supply, and Gecko drivers. The rack will incorporate a swing arm with keyboard tray, monitor mount, and a place to hang my lathe's control panel. It is fabricated of rectangular tubing. I'm further along than this, but here is a teaser pic:

Swing-arm goes on the pivot shaft at the rear. That's the PC enclosure sitting there. More to come!

Label Your Wiring!

As part of the process of building my enclosures, I have to take apart the working step motor driver enclosure. I want to drill the rear panel for every concievable connection I made need in the future so that once I have it bolted back together, adding a new feature will not require any chassis modification, it simply requires running the wiring to the GRex. Towards that end, I bought some cable marking products from CableOrganizer.com to make it easier to keep up with the wiring:

Label machine and the two cable marker dispensers. Middle one has labels you can write on, lefthand one has digits...

Here are the step motor cables. I labeled the axes on each cable. The numbers tell me which terminal number on the Gecko drive the lead goes to.

Concrete CNC Machines?!??

The first time I heard ships could be made from concrete I have to admit I was surprised. This was done in World War 2, though I am not sure how often since. There is one partially sunk on the beach near where I live. So if you can build ships from concrete, why not CNC machines? Before we go further, here is a example from a company called CNCBridges (bridges are made of concrete too, eh?) of an expansion kit for the popular Sieg X2 machines that is built of something called polymer concrete:

It looks pretty nifty, doesn't it?

There is quite a lively thread at the moment over on CNCZone concerning polymer concrete as a material for building CNC machines. I'm going to try to follow it and digest it here so it becomes more concise. We will see what we can learn from it.

One of the first things brought up is that we are looking at composite materials, and that for this application, a composite of epoxy and granite is one of the best. Polyester (fiberglass) resin is considered obsolete for this application because it shrinks while curing. Epoxy supposedly has zero shrinkage, which is ideal. There are a lot of approaches to using the stuff. The pictures above have it case into the desired shapes for the machine. Another possibility has it filling a welded frame to damp resonances and increase rigidity.

There are a some higher end companies in this business, ITW Polymer Castings and Accures Casting. Accures has a "starter kit" that does 3 cubic feet (a weight of over 400 lbs) for $340. That would be an interesting place to start, giving they have probably worked out a lot of bugs in the process. Check some of the properties of their material: it damps 10 times better than cast iron and 30 times better than aluminum, for example. Precision Epoxy makes flooring products for the motorsports world. Check out their epoxy surface plat product. Very interesting. Claimed to be 0.005" flat just by pouring! They're using it for precision chassis set up on racing cars. Penske, AJ Foyt, and others use them. I guess that would require a big surface plate!

An article in Machine Design shows machines being cast from this stuff with accuracies claimed to be 0.001"! Light Machines has been building small mills out of this stuff for about 20 years. They use the ITW "Zanite" product.

For those who are wondering why ordinary concrete cannot be used instead of epoxy, the issue seems to boil down to shrinkage, extremely long curing times (months!), and water which may lead to corrosion of the metal components. Interestingly, Bamber, the fellow whose thesis Principles of Rapid Machine Design, I learned a lot from, uses ordinary concrete and rebar to damp the frame on the machine he built, and it produced excellent results. I wouldn't rule it out, but the epoxy looks set to produce a superior result at a higher cost.

Getting the exact composition right is interesting. You don't want too much epoxy, or you are building a plastic machine, not a composite machine. Apparently it takes a variety of sizes of media ranging from very small 20-200 micron size up to fish tank gravel (BB sized) pieces of granite or sand. I find myself wondering about bead blast media as a component when I read this?

Steel inserts are cast into place to provide threaded hole locations. Hexagonal cross section inserts are made that have a recess in the center to provide strength against pull out. They should not be placed closer than one diameter from the edge. One challenge for the DIY crowd is that achieving high accuracies means using very accurate molds.

One outfit trying to build a commercial machine weighed in with some tips. Here is a shot of the rail mounting on their small mill:

Linear rail mounting in polymer concrete...

Note the rails have a precision guide edge modled into the composite base. The base itself is L-shaped to support the table and the Z-Axis. So the Z and Y rails are bolted to the polymer base. Here are some of their tips:

Granite


"Decomposed granite" from landscaping places usually has a good mix of sizes and relatively smooth edges. If you want to get kind of fancy, you could probably separate the granite by size using appropriately sized wire screens, and then combine in an optimized ratio. This really isn't necessary, but I know some of us are overachievers...

Epoxy
Raw epoxy is solvent free and ships non hazmat.
Cheap reactive dilutents are used to thin the epoxy and thin the price.They also thin the properties.Ask your supplier if their epoxy contains Nonyl Phenol.
If your supplyer cannot ship non hazmat the epoxy has dangerous additaves.
Raw, neet epoxy has low vapour pressure{smell is not bad]
Reactive dilutents have very strong odour,might i add unbearable.Again if it ships non hazmat it is probably OK epoxy.To confirm request MSDS from the supplier.
We need thin epoxy to maximize filler loading.This would be called Laminating epoxy.Thinnest ? Probably 600cps which would be the consistancy of #one Canadian maple syrup.Suddenly I feel like bacon& pancakes.
Epoxy glue is 10,000cps or better.No use to us granite guys.Similar to honey.
We want a long pot life to maximize mixing time and reduce heat build up.Many times we have mixed or de gassed for too long and the epoxy is really hot.Now we are sweating granite bricks trying to get it in the mold fast before gell.
Molds

Some further tips from a German machine tool book include:

Aggregates from <0.1mm (Sand dust) up to 16mm (on the larger castings from 80mm section thickness). Whereby you want to aim for 1/5 to 1/8 your smallest feature.

Resin ratios by weight of 7% to 10%.

Shaking frequencies up to 70Hz and accelerations to 25 m/3 (2.5g) This is basically your industrial 2 pole motor with a unbalance. If you pick up a cheap motor and VFD off ebay, you can vary the speed until you hit the sweet spot for each casting. The largest castings use a combination of a shaking table and shaking motors bolted to the outside of the form.

For optimal bond, any steel inserts you bond into the part should be sand blasted.

The practical method for prototypes and us homebuilders is wooden forms with steel sections moulded in which are subsequently milled or ground to tolerance. The big guys are going more and more to cast to tolerance, but also do grinding of the mineral to tolerance. If you have a surface plate and an eye for detail, grinding and scraping alignment rails could be a garage job.

Tolerances to +- 0,5mm should be posible with wooden molds. Edge distance for inserts should be >3D. If you intend to reuse the form, it should taper about 5°. Round all internal edges.

A rule of thumb would be a polymer concrete machine base is made the same size as a cast iron part, but solid where the C.I part would be cored, should have nearly the same weight and approx 3.5x the stiffness.

As the shrinkage of epoxy occurs around the time it gels, much if the shrinkage is compensated by further filling of the still liquid mix. The final shrinkage is given as 0.02 - 0.03% linear.

One fellow has a clever idea, which is to partially sink 80/20 extrusions in the polymer concrete. This would deliver their precision together with the superior rigidity and damping the polymer provides.

As far as suppliers go, there is the Accures starter kit, or you could try to buy the materials from an online supplier like US Composites or Epoxy Systems.

The level of sophistication increases as the thread goes on. Degassing is a problem with epoxy. Mixing it embeds a lot of air. You'd like to get rid of the air. There are two methods. One, use a pain stripping heat gun. Keep it moving constantly! Two, try vacuum degassing. Someone pointed out there are vaccum systems available from auto suppliers that are designed to suck the oil out of a car. They generate 15 or 20 inches of vacuum, which is plenty to degass. Now you just need a suitable vessel to do it in. Vacuum systems are also used for veneering by woodworkers, and would also be usable for this purpose.

2/03/07

Rotary Table Accessories and Tips

I finally came across a project today that needed my rotary table. I've had it for awhile, but hadn't started using it yet. Before I could do so, I had to make a couple of accessories. I've started a page to gather up the tooling and tips I come up with for the table.

A Plate Machining Fixture and some Homemade T-Nuts for my Phase II Rotary Table...

Fish Tape Cable Guides

Given the cost of Igus and other "professional" cable guide solutions, I thought using an electrician's fish tape was a clever idea:

Fancy Brass Steam Engine

Lightening slots are very nice touch!

Semi-Enclosures

Here are some thoughts on mill enclosures that are a little less ambitious than a full enclosure:

Kap Pullen's enclosure. Look at the size of those collets in the foreground!

Need an Electromagnet?

Check out a coil for an auto air conditioning compressor clutch. They're easy to come by, relatively inexpensive, easy to mount, and pack a lot of holding power for their size.

2/02/07

Jib-style CNC Plasma Cutter

In the thread on a portable CNC plasma cutter, someone mentioned jib-style versions. I could not come up with an example from the Internet, but drew this quick sketch of one:

A jib-style plasma CNC cutter...

The sketch shows a 48" arm of 2 x 2 material, perhaps an 80/20 extrusion. The base is an 8" diameter cyliner, and the jib is supported at the end with a downlink. It probably makes sense to run that center shaft up high enough to hold the plasma cable above the fray. There is some engineering needed to make the rotating axis run smooth and true, but it isn't that bad. The Z can ride out the extrusion on a skate bearing arrangement of some sort.

It's an interesting thought, and I suppose given the needs of a plasma system, it could be quite light and doable. One could even imagine a magnetically attachable base.

I'll have to ponder this one further. Need to consider the programming implications on Mach 3 as well. Ideally, you want this to look just like a regular x, Y, Z gantry when programming. I'm pretty sure Mach can do that, though. One problem is the torch speed is going to vary wildly at different radii from the base. That alone is probably a reason not to use this design for plasma, which is pretty sensitive to that speed.

Later on, someone posted a link to this commercial version:

1/31/07

Kudos and Hero Worship for the Fidgiting Widgitmaster

This evening I have a number of posts below based on a reading of just one of the Fidgeting Widgitmaster's threads over on the CNCZone. I swear I learn something new from every one of the Widgitmaster's threads. He is truly an inspiration to the home shop machinist, and I would encourage you to hang on his every word. The Widgitmaster is a retired professional machinist, and his excellent photography and penchant to explain how he builds his parts give a rare glimpse into how things are supposed to be done if you knew what you were doing!

Widgit Engineering for a CNC Router

I swear I learn something new from every one of the Widgitmaster's threads. This time, I was sniffing around, dimly thinking about the portable plasma table I recently wrote about below and how I might built something similar. That table used skate bearings and angle iron for rails, and I'm sure that's a fine way to do it, but I wanted some a little nicer, and a little more precision. So I got to looking at how the Widgitmaster has engineered his router tables that he sells on eBay. I like his thinking. Here is one axis, which consists of a plate supporting a shaft with lots of support:

Plate with "v-block" supports for shafts...

He mentions the shafts warped like crazy when he cross-drilled them and he had to straighten them using his surface plate, some v-blocks, and a dial indicator. The mating piece that slides on the rods is also quite cleverly done:

Delrin nut and bronze bushing material...

He uses some bronze bushing material, split, to ride on the rails. The but that rides on the ACME leadscrew is a chunk of Delrin inserted through the bottom hole, and then cross bored and threaded with an ACME 1/2-10 tap. These Delrin nuts are excellent in terms of being relatively cheap and having minimal backlash on an ACME screw. Perfect for this kind of router or plasma application.

These are the relatively small Y and Z axes. For the larger X axis, he uses Thompson ball bushings instead of the bronze, and they're held in the bores with some spring clips. The only thing about the ball bushings, is they would not allow the shaft to be supported in the middle. I suspect that one can buy split ball bushings to overcome this. For Widgitmaster's application, it didn't matter, he was going 12" or so with 1/2" shafts. The shafts are hardened and ground drill blanks

Next he goes on to make an awesome clamp from aluminum. Check out the "sneaky drill" he made by grinding the middle down on his surface grinder to get at the holes inside the clamp:

Dremel clamp and "sneaky drill"...

Sneaky drill allows clearance to drill the clamp holes without removing it from the vise...

Here is one of the little mini-routers all finished: Cool!

Widgitmaster's Plexiglass Cutting Secret

Buy these end mills from Enco:

.0400 X .125SH SOLID CARBIDE MINIATURE 2 FLUTE DECIMAL END MILL
Type: Regular Length
Number of Flutes: 2
End Type: Centercutting
Size (Decimal Inch): .0400"
Shank Diameter (Decimal Inch): .1250"
Shank Diameter (Inch): 1/8
Length of Cut (Decimal Inch): .1200"
Overall Length (Inch): 1-1/2
Material: Solid Carbide
Tolerance: +.000-.002


Model #325-2285
Low Price: $6.89 ea

This is but one of hundreds of sizes and types to choose from!

When cutting Plexiglas, put a dab of dish-soap on it with a small brush!
It will give you a crystal clear finish with these cutters!

Widgitmasters states that the trick with plastics is to never cut them dry. He also cuts them with mineral oil too.

Widgitmaster's Mondo Vise Jaws

I just let things hang over the side and machine them anyway like a noob, but the Fidgeting Widgitmaster has special jaws for his Kurt vise:

His are longer than mine! Doh!

I'm also noticing how narrow the step is on his jaws. I need to rework my vise jaws here!

Widgitmaster Machines A Big Chuck O' Aluminum

I bought a set of 2-4-6 blocks after seeing Widgitmaster use them to help support a big plate he had stood up in his Kurt vise. Here is another patented Widgitmaster setup, allowing him to machine the edge of a big plate of aluminum:

Dee plate. I love Kant-Twist clamps too!

Behind the curtain, here is how it is done: stacked 1-2-3 blocks, 2-4-6 blocks, angle blocks, and big box blocks...

A shot in front of the curtain with the plate not yet in place. I bet dialing in the plate was a twitchy operation!

Another big piece setup. Note the sine bar and plastic pieces protecting the aluminum from the clamps. Surface finish on the aluminum is similar to what I get with my indexable face mill...

I read of a lot of machinists saying they haven't used a sine bar in years and recommend not buying one, but here is Widgitmaster cranking away with one. If you ask me, either these other guys are all running CNC or they just have forgotten how to use a sine bar.

 

Widgitmaster Production Line Technique

First, square all of the blocks to be used for each part. Widgitmaster uses a 6 insert carbide indexable face mill to do the squaring. Next, put the blocks into boxes with a print on each box showing what the part should be:

Dem chips shore do pile up high after squaring the blocks!

Widgitmaster on Accurate Boring

First drill the hole 0.050" smaller than the final bore.

Next I setup the mill for boring the close tolerance holes for the Ball Bushings, fortunately I have a nice Bore Gage with a 2" dial and .0001" accuracy!

I also have a 50-millionths electronic micrometer, and have used it in the past to set the zero on the Bore Gage, but its too awkward to position the small contacts of the Bore gage on the little anvils of the micrometer! So I found time to turn a Master Ring Gage for setting zero on my Bore Gage!

The .500 Linear Ball Bushings require a hole that is .87440 diameter with a ±.0002" tolerance!

When I do really close bores, I take a rough pass with the boring bar, and then take a second pass at the same settings and speeds as the first. Then I get my measurement as accurately as possible, make my adjustments to the boring head and then take two more passes.

When set properly, I can do a rough and finish pass and get the bore to repeat within .0001 all day long! But whenever using instruments with .0001 accuracy, you have to keep them in the same room for a few hours so they all become the same temperature as the machines! The heat of your hand can throw off your readings really fast!

The skill is in the adjusting of the boring head, and sharpening of the boring bars!

For even more accuracy than the bore gage, look for a used Brown and Sharp Intramik on eBay.

Widgitmaster Internal Grooving Tool

Here's something to make from end mills gone bad:

Shopmade Internal Grooving Tool...

Widgitmaster uses a Wohlhaupter boring and facing head with this tool. It advances the cut automatically each revolution until it reaches a pre-determined stop. I will sheepishly admit I own a Wohlhaupter but have not yet dared to try it. First, because it was expensive. Second, because it is crazy complex to figure out. Even the Widgitmaster positively refuses to give a tutorial on it.

Wohlhaupter with grooving tool all set to go. Widgitmaster is cutting the grooves for retaining spring clips for some Linear Bearings...

Widgitmaster's Sneaky Way to Check Your Feeds and Speeds

Measure the thickness of your chips. They should be about 0.006" for aluminum. Think about it. It's just the chipload per tooth of the material you are working on!

Widgitmaster's Methods of Centering On Holes and Other Features in the Mill

Here are the tools he uses:

Left to Right, Top to Bottom: Edge Finder, Dial Indicator, Corner and Edge Finding Blocks, Widgitmaster's Precision Hole Indicator Widgit, Indicol Indicator Holder...

How many do you own and use? I would like to get the edge and corner finders, but I have all the rest. I need to use them more often and quit trying to just eyeball everything!

Thanks for all the Help, Widgitmaster!

I want to conclude this "Widgitmaster Series" with a sincere thanks to the Widgitmaster. I just purchased one of his little router mills off eBay. That makes my 3rd milling machine: I have 2 IH mills and now this little guy! I have no idea what to do with it, but the idea of a tiny little mill was irresistable as was the delightful thread about its construction and design. Lord knows I have enough extra step motors and stuff floating around here I can probably get it running. Maybe I'll bring it into the office to show my cohorts just how crazy I am. I reckon the knowledge I've gained reading Widgitmaster's various posts was well worth what I paid for this little mill, so it's just another way for me to thank him.

1/30/07

Nicely Made!

I recently saw this item on eBay, and got to admiring how nicely it is finished. It is an "Ornamental Turning Horizontal Milling Cutting Frame", and I have no idea what that is, but I would like to be able to finish my shop made tooling so it looks this nice:

3 Double Vises: No Waiting!

Here's a nifty setup on a Haas Mini Mill:

3 double vises = 6x the capacity of 1 vise!

They're Kurt knock-offs. The fellow says they work great. They sure let him set up a lot of parts at once! He has a business making precision shooting goodies at Seekins Precision. Very nice!

Managing the Chips in Your Flood Coolant System...

I don't know when I will decide to implement a flood cooling system, but it seems inevitable once I get onto CNC. The biggest challenge will be an enclosure so the whole shop doesn't take a hosing down in coolant and chips when I fire it up. A secondary challenge will be managing the chips that run around the system. They will screw things up if the pump ingests them, and it would be nice to have a method to separate them from the coolant return flow and make it nice and easy to clean them up while we're at it. Others have discussed this problem at many times.

Enter ChipTrap. This is a product intended for the purpose that looks very easy to reproduce in the home shop. Imagine you have a round hole at the bottom of your enclosure through which the coolant is expected to drain into a big tub with pump that sits on the floor underneath the hole. Chip Trap is a removable plastic tray with filter that captures the chips before they drop into the tub reservoir with the pump. It looks to me like nothing more than a rectangular plastic tray with a holey bottom and some fish tank filter floss pad or similar material sitting atop the holes to catch the finer contaminants. Change the filter floss every so often when it gets too nasty, but otherwise just flip the thing upside down and the chips go into your recycle receptacle (or whereever). The hole at the bottom of your enclosure also becomes a handy way to collect chips out of the enclosure. Move the coolant reservoir out of the way (maybe it goes on a furniture dolly or some such), put a collection bin underneath, and sweep 'em out the hole and into the bin.

There is apparently a stainless steel strainer/colander used in the food service industry called a "China Hat" (seems not very PC!) that can also be well used for this. Another fellow suggests making sure your coolant system can be quickly rigged to flow in reverse and flush itself out. Several suggest running a whole house filter on the pump pickup to keep it clear of trouble. These are just 40 mesh stainless strainers available at plumbing supply houses with 1/2" NPT fittings. Seems a good idea.

One last thought someone mentioned was putting some screening around the base of their mill so the chips wouldn't wind up underneath. That seems a pious thought and is one I will incorporate if/when I get around to my own flood cooling system. Miles to go before I sleep or even think of getting to that though!

1/29/07

Mysterious Vibration in My Lathe, Better Finishes, and Fenner Belts...

For a while now I have been ignoring a slight vibration in my lathe, hoping it would go away. Stupid, I know, but I will be the first to admit I am lazy!

Finally tracked it down. I happened to be fiddling with setting up my 4-jaw chuck and spinning the spindle by hand when I felt a little "pop" in the motion. I thought, "Oh boy Virginia, this is the big one, my spindle bearings have gone!" So I opened up the gear area and fiddled around until I got the pop to repeat itself. Suddenly it all became clear. My timing belt was not tensioned quite properly and it would occassionally pop a tooth out fo the timing belt pulley.

SWEET RELIEF!

I suspect the motor shifted a bit. What I need to do is work out a proper tensioning arrangement. I either need to mill some slots on the motor mount (I didn't own a mill when I made the original DC treadmill motor mod 2 years ago!), or install some kind of an idler. It's funny because the vibration would disappear if I revved up the spindle rpm, and then I would back down to the desired rpm after the vibe was gone. I looked at the belt and it didn't seem worn, but its a wonder it didn't wear through.

What has all of this to do with finishes and Fenner belts? Well, I was reading another thread about a guy putting a real 3 phase motor and VFD on his mini-lathe and it jogged loose some memories of other threads and thoughts. First, I have read and been told in more than one place that a lathe running 3 phase will simply leave a smoother finish than one running single phase. Evidently you can see the pulsing of the motor on fewer phases in the finish. Hmmm, says I. Now another fella on this VFD thread opines as how he things timing belts give a rougher finish than v-belts. Hmmm again, says I, and I suddenly recall reading that running the belt a tad bit loose is good for surface finish. I think that's an old SouthBend trick or something. Now the timing belt can't exactly be loosened, or it starts to skip a step every now and again, like mine is doing.

So, methinks I ought to consider swapping out the timing belt for something else. I don't know if this will improve my finish or not, but I have heard that the best belts for reducing vibration are Fenner belts. That link is just one source, I've heard it in a lot of places. It sure is tempting to look into a Fenner (also called a "link" belt) that would fit the lathe, swap out my pulleys, maybe consider a little different ratio, and get a proper tensioning arrangement. OTOH, one fellow has reviewed every belt known to mankind and feels the vibration advantages of link belts are marginal compared to cogged v- belts.

Yippee, more stuff I won't find time to get to!

Portable CNC Plasma Table

For those of us who have big garages, but that still do not have enough room for:

- A 4' x 8' router table

- A 4' x 8' plasma table

- The loading dock and forklift needed to feed said 4 x 8 machines with raw material

- A full sized CNC mill or VMC

- A full sized CNC lathe

- A good sized welding table to Tig/Mig all those newly cut parts together

- A decent workbench/worktable

- Rollaway tool chests for all the goodies

- yada, yada, yada

Thank you! It's about darned time!

A portable/swing away/doesn't-take-a-lot-of-room-when-not-in-use-plasma table seems like a beautiful thing. I'm sure someone must have done this before, but this is the first time I've seen one that is simple and is meant to be put aside out of the way when not in use. I would love something that pivots down over my welding area or some such. This fellow has created a "clamp on" CNC plasma cutter:

A Clamp On CNC Plasma Cutter...

Trigger Mechanism is a Fixed Chain (Wingnut adjusts tension) that is pulled as the Z-axis lowers: Low-Tech KISS Works!

Another fella on the thread mentions he had a little 20" x 20" cutter that was designed to sit on top of a 55 gallon drum. I love the idea of these little machines! How often do you really need to cut a 4' x 8' sheet of metal? At home?!??

I also love his dead simple trigger mechanism, which is simply a chain that squeezes the trigger as the Z-axis is lowered. His only complaint is he says the skate bearing on angle iron guides sometimes bind up. I think that could have to do with the fact that he is driving it on one side only and not in the middle, which will make his gantry "cock" a bit.

Other than the cost of the plasma cutter itself, its almost ridiculous to consider how cheaply one of these little guys could be made. Very small step motors, low end smaller drives (no need for Geckos), and a quick and easy breakout board oughta do it. Biggest issue is gonna be dragging a PC over by the durned thing to run it. I suppose if you run an NCPod, you could just plug a laptop into it as needed.

Rhino Cage Editing...

Someone asked on one of the boards how to take a flat leaf drawn in Rhino, and curve it to look more realistic. I thought of the new "CageEdit" command in Rhino 4, which basically lets you deform an object by grabbing control points on another object. I drew the flat leaf by tracing a curve over a bitmap and then extruding it to get a 3D surface. I then drew two lines and used them to deform the leaf along two axes. The result works for me:

1/28/07

And Now For The Really Fancy Stuff!

Here is a job that uses some very sophisticated shop-built indexing fixtures to make 6 aluminum manifolds at a time on each of 2 Haas VF-3 machining centers. First the parts:

Complex aluminum manifolds are machined on all 4 sides!

A view of the custom built indexing fixtures. They even incorporate an Omron switch used as a tool height sensor...

So what all is going on here? Well the job requires 41 tools (thank my lucky stars these VMC's have tool changers!), each block has 140 holes (holy mackerel!), and most holes require custom form tools with 3-4 different diameters +-.001. and different angles and square bottom. The custom indexer holds 6 blocks, and can position them at 90 degree steps so all 4 sides are accessible. The indexer was built entirely from parts ordered from McMaster-Carr and cost about $3000 and 2 weeks to build. Each block has 2 side plates screwed in that mate to the indexer. Another machine is used to drill some really large holes before the blocks are installed in the fixture.

The indexer is powered by air, and the center section has the power. Clamping force between centers on the blocks i 5 tons. The fixture locates the blocks on 90 degree intervals with adequate precision that they are delivered raw and squared in the indexing fixture. The inside of the fixture includes an oil bath, which has kept things running smoothly and precisely for 4 years.

The job would have required 60 tools, but the changer only accomodates 41, so the machinist had to get creative. One trick involved modifying the end of a tap so it could be used as an engraving tool to put the lettering onto the parts. All tools on the job are cryogenically treated, which the machinist said increases their life 2x to 3x.

These machines run 24x6 lights out, usually only 2 shifts--a day run and an overnight run. They routinely make 12,000 to 15,000 parts a year.

This is how the really good shops make money--this guy can make these parts more efficiently than anyone else after setting up like this.

Home Shop CNC Parts

What have people made with their CNC machines at home? I thought I would start this gallery.

A Sample from the Gallery: Done on a Round Column Mill Conversion!

1/27/07

Starting Up a CNC Business

There are some pretty good gems I saw in a PM thread recently. I've been trying to make my own list as well for people to consider. I try to combine what I've learned founding software companies with what I'm learning about the manufacturing and machining world. Some thoughts:

1. There's more money in products than running a job shop, but only if the product is differentiated.

A differentiated product is one that is unique. Differentiated products have an innate profit margin because you are the only supplier. Hence, they offer profit. Job shops are all competing to see who can do the same things more cheaply, hence they are commodities and margins are thinner. If your shop has a special skill or capability to bring to the table, you may beat this.

But, it's hard to find the right product. Once you have found it, you may sell it for a while, only to find out later that someone copies it and sells it more cheaply, leaving you with an undifferentiated product and a business that suddenly makes a lot less or no profit. The moral is that you can never have too many products. You'll need to budget time to always be working out new products that nobody else has.

Investigate ways of protecting your products from being copied as well. Patents are a good example.

2. The most important thing when you are starting out is learning.

If you are not already a trained machinist, start out small and consider every learning opportunity to be of great value. Consider that your learning may limit your ability to make profits in the short term. View it as a long term investment, but keep the overheads low until you can cash in on your learning by being more productive.

Learning also extends to the market and product, not just the machine work and manufacturing efficiencies. There is a lot to learn in running a soup to nuts manufacturing business. Be sure to plan for the "learning expense" so you won't be surprised if everything takes longer and is more expensive than it ought to be.

3. Small business needs to keep overheads low. Profitability is elusive, capital is scarce, and it can lead to an expensive failure if overhead gets out of control.

Towards this end, there are a lot of ways to learn and be productive while keeping overheads low:

- Buy a used or hobby class machine to start learning on. Restoring a used machine is a learning experience that will teach you a lot of good machinist basics. Some of this you'll have no time to learn if your product "hits it big", but you need that foundation.

- Sub out volume production at first. Focus your efforts on prototyping and finding the right product.

- Beware of debt. You can buy a much better machine with financing, but are you ready to use it? Those interest payments will go to funding your education. If you are a trained machinist with a good product idea ready to go, time to market may make it worth diving in. But what's the hurry? You could as easily still sub parts for quite a while.

Don't Underestimate the Pipe and MDF Router Crowd

You can actually build a darned nifty CNC router from MDF and pipe:

Corian inlay done on an MDF and Pipe Router!

This is the router under construction. Plans available on CNCZone for free!

One guy even built an automatic tool changer for it!

Quite A Lot of Info on Setting Up Mach 3 For Tool Changing Here!

When a Toolpost Grinder is Just a Grinder

Whoa!

Grinding a ballscrew OD for bearings. Oughta cover those ways!

1/26/07

Increasing Height Gage Accuracy

After reading my HSM post on the Z-axis presetter, one fellow recommends replacing the scriber on the height gage with a tenths DTI for increased sensitivity and accuracy. Great idea, and I've no doubt it would greatly increase the accuracy of one of my favorite measuring tools.

Hones are the Way to Go Rather than Toolpost Grinders for Tenths Work

Amid an interesting PM thread on the better grades of Asian lathe (a subject of great interest to me, but I digress), I found Forrest Addy popping up to talk about honing. The thread starter is actually the same fellow I bought my second IH mill from. He is looking to upgrade his lathe to a machine capable of doing very precision work in order to fit ABEC-7 bearings to ID/OD tolerances.

The responses are interesting, with many responders dismissing this as a task that is not well suited to a lathe. Professional machinists will advocate grinders, and will pretty well dismiss lathe toolpost grinders as inadequate at best and very damaging to the lathe (abrasive grit, you know) at worst. Nevertheless, one does sometimes want to fit bearings, and I am no exception to this. I had read on 5Bears site of some techniques which looked like the best approach for an HSM. One must take into account that Swede (who runs the site) is an exceptional machinist, and that he is doing the work on a Hardinge lathe (or clone), which was designed for precision from the start. Nevertheless, I have meant to give these techniques a try. What's lacking at present is sufficient time spend improving my HSS tool grinding skills to get the geometry that Sweded recommends for a fine shaving cutting tool:

5Bears tool for making very fine cuts in steel...

Swede comments that you can make cuts no greater than 0.004" with the tool, but that by using your compound at an angle for infeed you can cut as little as 0.0002" or less! That would be handy for sneaking up on tight dimensions.

What does all of this have to do with Forrest's comments? Nothing really, I'm just setting the stage for my understanding of how to get to these tolerances on a lathe, and as we'll see, Forrest feels he has a better mousetrap. According to Forrest, regardless of whether he is using a brand new Monarch 10EE or a clapped out lathe, he doesn't bother getting closer than 0.001" with his lathe:

I shoot for + a couple of thou oversize and dress it down to size with a Sunnen external honing stone. I have sunnen honing stones I've cut in halves and thirds each to support specific bearing fits. They not only make sneaking up on the size duck soup but round up and refine the tooled finish as well.

A little artistic work with a slip stone or 320 grit wet or dry backed up with a flat file works well too but there's no rounding action. With careful micrometer feed back and reference to a thermometer and a accurate size standard, you can hit 0.0002" size tolerance on a short diameter in very little time.

I have heard him mention these hones before. Apparently the maintain the roundness very well, and create a precision result. Forrest has been around the block so many times that I would trust what he has to say implicitly. I have asked him for more information from him on the HSM board in hopes of getting more detail on this technique.

Forget Seeing My Etchings, Would You Like To See My Laps?

There are many great contributors on the HSM board, and McGyver is one who is very understated, but does excellent work and whose advice is always worth a listen. His response to my post asking Forrest to explain honing was to suggest lapping. In the post he presents pictures of a collection of laps he has made to facilitate piston work on model engines over the years:

Each one uses soft copper so the grit will embed in the copper, and each is adjustable as well. McGyver advocates using the laps handheld at low speeds for a precise feel of what's happening to the bore.

What a neat and well made set of shop tools for precisely setting up cylinder bores!

Now, FWIW, I have heard Forrest Addy advocate brake cylinder hones for similar purposes.

World's Best Way to Set Up a 4-Jaw Lathe Chuck

Another great HSM thread raised the perennial "How do I set up my 4-jaw" question. I didn't expect to learn much, but as soon as you think that, the world throws you a new curve ball that tells you to pay closer attention. Buried in the thread was what sounds to me like The World's best Way to Set Up a 4-Jaw Chuck. The technique requires no more than 2 revolutions of the chuck, and is performed as follows:

1. After rough aligning to the chuck rings, using a dial indicator on the work-piece, rotate the spindle through one complete revolution noting the highest and lowest indicator readings;

2. Continue rotating the spindle and halt at exactly Midway between the above two readings, then zero the indicator bezel to the needle;

3. Rotate the spindle to bring jaw #1 ‘on plunger’ and adjust jaws #1 and #3 to re-zero the indicator; finally

4. Rotate the spindle 90 degrees and adjust jaws #2 and #4 to zero the indicator once again.

This is one of those things where I read it, it made total sense, it was elegant, and it made me feel stupid for not having thought of it myself.

Accurate Lathe Work On a 3-Jaw Chuck

Wow! The action on HSM won't let up today.

This is a note from Sir John Stevenson from the same thread as the 4-Jaw setup method noted below. His position is that time spent changing chucks is time wasted, and that one can do work in a 3-jaw accurate to 1 or 2 thousandths. He admits to it being controversial, but holds his ground from an economics and efficiency point of view. John is always worth listening too as he is a very talented professional machinist and inventor.

What are his secrets?

First, he rapidly converts a 3-jaw setup to turn between centers for work that has to be removable. This is done by turning short pieces to act as centers and then catching the lathe dog on the chuck jaws to turn the piece. I admit I had heard of this trick before, but it is a very good one.

His second secret is all about getting the work done without removing the workpiece from the chuck. He is correct when he says that any crap 3-jaw turns fine, the setup is just not repeatable. So, turn the full length diameter, don't try to flip the part around. Turn inner and outers that have to be concentric in one sitting. Again, this is good common sense, and a practice I had already been following out of sheer laziness and fear of screwing things up if I didn't get things all done in one setup.

Kap Pullen (whom I bought my excellent Phase II 8" Rotary Table from) amplifies on John's tips with a few of his own:

1) If the job runs out a couple thou in the chuck, put a .001 feeler under the high jaw to bring it in.

2) Rough it ALL out before you start to finish.

3) Make all finish cuts in the same setup (chucking).

4) For multipal parts, do the job in operations leaving a finish true up cut. Mark the stock, and one jaw, to reset the parts in the chuck the same way.

5) I turn a chucking diameter to hold on to that will prevent the stock pushing back in the chuck. This is the piece John cuts off and discards.

6) On thin wall parts, make a plug to support the jaws, and/or chuck very gingerly!

7) When making the finish cuts, turn the machine on before you move that dial. Even a fine lathe will creep a couple tenths from cross feed screw pressure from the starting vibration.

Computer Wheel Balancer?!??

There was an interesting thread on HSM that really got my wheels turning. It introduced one of those, "Aha! I never would of thought of that, but it sure makes sense," moments. It seems this fellow had just gotten a smoking deal on a computerized wheel balancer:

Snap-On WB400 Wheel Balancer...

As you may or may not know, I fool around with cars quite a bit, and I could almost justify a balancer and wheel mounter, but not quite. I wouldn't use them that often, and they would take up enough room in my shop for another lathe or surface grinder. But there is more here than meets the eye. First, this is a really compact unit, which would save on space. More importantly though, were the remarks that the balancer could be used to balance almost anything if one were handy enough to make the appropriate adapters.

Whoa! The lights went on! You can use this to balance almost anything!

Now they had my attention. There've been a number of articles I've come across on balancing tools and machines to improve their performance, and its something I've wanted to learn more about. For example, I recently read about a guy that bought what he thought was a nice American Iron lathe of some kind, but it had terrible vibration above 600 rpm. The guy thought his bearings were shot and he was looking at a costly tune up. A professional machinist friend came over and they rapidly determined that the only problem was his chuck was out of balance. They balanced the chuck and the machine ran smoothly and quietly up to max rpms. The idea that a gizmo like this could make work like that real easy to do and would work for tires too is fascinating to me.

Another interesting post in that same thread mentions driveline balancing. One fellow was familiar with a shop that did it using a converted lathe. The stick one end of the driveline into the 3 jaw chuck. The far end goes into a stead rest made of 3 Go kart tires. The tires are inflated to grip the shaft, and the works are spun up to 500 rpm. In the toolholder goes a piece of chalk, which is advanced slowly until it starks to chalk part of the shaft. The chalk will mark the heavy part of the shaft. Weights are attached with hose clamps and the process completed until the chalk goes all the way around. I tell you this balancing stuff is a fascinating. I have visions of tuning up my Chinese machines until they run smooth as silk. Oh well, we have to dream don't we? LOL

1/25/07

Making Fan Covers with an Industrial Hobbies CNC Mill

I wish I could lay claim to this excellent work, but a fellow over on CNCZone did it:

Cool cover isn't it? He used a 2 flute end mill at 3000 rpm and 3-4 IPM feedrate. That's just about exactly what ME Consultant Pro would recommend. He said the job took 4 hours with a 1/16" DOC. FWIW, ME Consultant Pro would recommend a 0.1" DOC, which is not quite 2x the depth, and so it might halve the time on the job. For coolant, he ran a Noga mister with Kool Mist.

I love seeing the parts people make on these machines. Amazing how professionally they come out, no? A shape like this fellow's fan cover would be really hard to do manually without CNC too. He said he started the run, shut off the lights, and came back hours later to find his part finished.

Machinery Rigger's Delight: Lift Platform Trailers

Are you a home shop machinist who dreads the idea of recieving new machinery to their shop because of the ordeal moving the machine in can produce? Perhaps you even hesitate to look at a lot of machines for sale because the challenge fo lining up rigging and trucking seems like too much trouble? I have those problems, much as I like to purchase toys. I live in a house that has a steep driveway. 18 wheelers that show up will often drop their load at the bottom, refusing to come near my garage shop. I had my little surface grinder sitting down below for almost 2 weeks until I could get my brother to help me rig up a means of dragging the crate up the driveway to get it situated.

While people complain that they don't live in the rust belt where great old machinery is plentiful and cheap, there are a remarkable number of "deals" that appear withing driving distance of a couple of hundred miles. What the heck, if something shows up in Southern California, I can take the kids to Disneyland while we pick up dad's new pride and joy! Except I have no way to haul said pride and joy around. U-haul is a possibility, and I keep thinking of getting a trailer to go get the steel so I can build my smoker, but then I saw this thread on PM and loved the idea:

Pride and joy (Monarch 10EE, drool!) fits on trailer like any other...

Trailer can lower itself down flat to the road!

Machinery can be slid off the back, preferably with an electric pallet jack...

This fellow said his trailer was a Primco 660T with a capacity of 4000lbs on the single axle. Others I found on the Internet include:

Bil-Jax: Elevating platform trailers. Several sizes.

Lift-A-Load Trailers: Nice, dual axle versions available.

Trailevator: Elevating platform trailers. Lower capacity, probably not that suitable for machinery moving.

I would love to track down a trailer like this, though I would prefer a dual axle model. I would put a winch up at the top and with a pallet jack there wouldn't be much you couldn't go get with one of these!

1/24/07

Accurate Z-Axis Adjustment on the Mill (aka I love it when a gadget actually works!)

In working on the Turner's Cube, being able to determine Z-axis precisely is imperative. In addition, I am still having a hard time achieving the level of accuracy I routinely get on my lathe over on my mill. On the lathe, getting it accurate to a thousandth is never a problem, and even if I am not paying much attention, things come within 3 or 4 thousandths. I haven't spent much time fiddling with tenths yet, but someday I will. On the mill, I seem to be doing good if I hit the high single digit thousandths, say accurate to 7 or 8 thousandths. I know its my technique, and its just not good enough.

I mention somewhere below that one has to allocate time to experimentation, so tonight I resolved to experiment with z-axis accuracy, and along the way, dug out a purchase I had almost forgotten to test for the purpose. In the end, I tried four different methods. In each case I used my granite surface plate and digital height gage to determine how closely I had come.

Using the granite surface plate and height gage to determine z-axis positioning accuracy...

To use the height gage, I zero it on the 1-2-3 block and then add 1" to the reading off the top of my aluminum cube. On the mill, I used each of 4 methods to find the top of the block, zeroed my quill DRO, dialed in a desired depth of cut with the fine quill adjustment, made the cut under power feed, and then checked how close I came to the expected result. Incidentally, the process of finding the top of the workpiece (or side on a lathe) is called a "touch off."

Here are the results of each z-axis setting method:

Touch off by feel: For my 1st Method, with the spindle stopped, clunk down the cutter onto the top of the workpiece. Zero the DRO and go from there. This produced a result with an error of 0.012". Not very good! The error was relatively repeatable, so one could add the fudge factor. In the end of the day, the cut was 0.012" deeper than desired.

Touch off by sound: For my 2nd try, I was gently lower the spindle under power and listen for when the cutter started to cut. This method proved slightly more accuate, and resulted in 0.0085" too deep a cut. Still not very good.

Touch off with paper: The traditional old school method involves holding a piece of cigarette paper (rumored to be exactly 0.001" thick) on the workpiece and gradually lowering the cutter until it starts to catch the paper. Add another 0.001" and you are at zero! Not having any cigarette papers, I used standard laser printer paper. I cut a 1/2" wide strip so I could hold onto one end from a safe distance, and waited for the cutter to grab. In my case, I got a grab at 0.010", not 0.001", but at least it was a nice round number and pretty repeatable.

Z-axis Presetter: At this point, I thought I was done and would be using the good old paper trick. But I had a vague recollection that finally came back to me. Did you ever by a gadget that looked like a good idea, but before it ever arrived you started doubting it would work well, stuck it up on a shelf, and never actually tried it? I do that way too often. In this case, thing I remembered was a Z-axis Presetter I bought off eBay around 8 months ago. Search for "Z Axis Presetter" on eBay, and you'll find the ubiquitous 800watt listed Chinese machine tool gadget. They look like this:

A Z-axis Presetter from eBay seller 800watt...

I have a dim recollection of some CNC guys recommending one of these to use with CNC machines. How does it work? Simple. There is a little knurled knob visible on the bottom left. It has a "test" and a "use" position. Set it to "test" and an internal standard swings into place so that if you press the anvil on top with your finger until you hit the stop, you'll have exactly 2" from top of anvil to bottom of gadget. You rotate the dial to zero in that position. Now reset the knob to "use", place it atop the workpiece, bring the cutter down until the needle registers, zero the needle, zero your DRO, and you should be exactly 2" above whatever the presetter is sitting on.

So, not expecting much, I plunked the sucker down atop my aluminum cube in my Kurt vise on the mill, cranked the head until the cutter almost touched. Locked the head and cranked the quill with the fine adjust until the needle zeroed, zeroed my DRO, removed the presetter, cranked down another 2" with the fine adjust, zeroed the DRO again, added 0.010" for a modest cut, ran the cube through under power feed, and hauled the block over to the surface plate to see what I had done.

The desired result was 2.396". I brought the height gage down to take a reading which was, drumroll please, 2.396"!!!!

Holy uncanny accuracy, Batman! The silly presetter actually worked, and it worked well, and even though the quill travelled 2", and I expected the worst, it came out deadly accurate!

Hooray for the gadget that actually worked. I guess I'll be using the silly thing more often. At $39, it was worth it!

1/22/07

Turner's Cube Dimensions

The Turner's Cube is a fascinating object. In the old days, novice machinist's were handed one and told to work out how to make one of their own. It was considered a good test to give a budding machinist to see whether they could first understand how to go about making one and second to see whether they could operate the machinery to the level of precision needed to produce a nice cube. After seeing enough different examples go by on the web, I got the bug and decided to try to make one. Working out the dimensions is the first problem. For a given cube, one needs to understand the diameter and depth of bore needed to produce the desired effect. This sounds like a job for a spreadsheet!

The depth calculation is fairly easy. Take the total width of the cube along the dimension parallel to the bore, subtract the desired width of the interior cube whose face the bore determines, and divide the result by two. This is how deeply you must bore a hole to reach the face of the hidden cube in each of the 6 faces of the overall cube.

The diameter of the bore is a bit trickier. A circle that circumscribes the face of a square, meaning it just touches the square at each corner, will be the square's width divided by 0.7071 in diameter. A circle that just fits inside of the square (the "inscribed" circle) will be the square's width in diameter. If we cut to the circumscribed diameter, the inner cube will be freed, and will not stay inside the overall cube. If we cut to the diameter of the inscribed circle, we only see holes, and the edges of the inner cubes will not be visible. I came up with the idea of an "overlap" parameter that interpolates between these two values. Simply take the difference between the two, multiply by the overlap, and add it to the inscribed diameter. As a percentage, the overlap tells how much of the square's edge will be opened up for view. I found through a few quick iterations looking at Rhino 3D models that about 75% seems to create a pleasing result:

A Turner's Cube Dimensioned by an G-Wizard Calculator...

I'll write up the overall project on its own page, but I thought you might enjoy seeing how the dimensions are calculated.

1/19/07

New Blog Index

I've added an index page for the blog. I do not guarantee to keep it always up to date, but I will be working it from oldest to newest. I got tired of having to search every blog page to find things.

Tip: Holding a Big Plate in the Kurt Vise

Put the jaws on the outside of the Kurt vise to hold a big plate...

Slick Lathe Carriage Stop

These are not something you'd need with CNC, but are really nice for manual work. This fellow's was unusually well done out of black anodized aluminum. It looks using a quick twist of the knob to turn an eccentric pin:

1/18/07

Spindle Bearing Lubrication

I decided to explore the bearing speed factor (dN) for my spindle design project this evening. It's a simple calculation to make that just involves spindle rpm, bearing ID, and bearing OD. What's interesting is the results help you to understand what sort of lubrication is needed. It turns out for my planned speed regime of 6,000 to 8,000 rpm, I am near a transition between just greasing the bearings and using some form of oil lubrication. This chart shows the results:

I'll have to think carefully about whether I really need 8,000 rpm or could live with 6,000 to 6,500 rpm, which would be solidly in the regime where the factory grease in the bearings should be fine. A 1/8" end mill ideally wants to run at 8,500 rpm with aluminum, and a 1/2" end mill can live with 4,000 rpm according to my copy of the excellent ME Pro software that I use to figure feeds and speeds.

1/16/07

CNC Lathe Progress

My brother and I got busy weekend before last and welded up most of a rack and swingarm system to hold the PC and driver electronics enclosures for the lathe. It's not quite finished, but it's come along quite well. I think I will really like the form factor. The swing arm was easily fabricated too. I'll give some pictures when I get the thing painted and a little more presentable. No rocket science here, just rectangular tubing and Tig welding.

Tapered Drawbar Spacer

I came across this idea over on the HSM Board, and I think its great. This fellow replaced his drawbar washer with a tapered spacer that does a better job of keeping the drawbar centered:

Every now and then my drawbar gets cocked a bit and the powered drawbar has to work to engage the socket to it. It manages, but a bushing like this would make things run more smoothly.

Update 1/26/07: I made my own spacer. It took all of a half hour. Boy, what a difference! I made mine to fit fairly snugly in the spindle and leave a nice easy fit for the drawbar to go in and out. The drawbar is now very closely centered every time, the spindle seems to run more smoothly (better balanced or just my imagination, who knows?) and it was well worth doing. I am updating the drawbar page to reflect that this is a "must have" part of the project. I think it will reduce wear on the drawbar nut since the socket will be closer to right on.

Take Time Out to Experiment

It's good to take some time out to experiment and try some new things. This last weekend, other than picking up my second IH mill, I took a little time out to experiment. I tried to grind an HSS lathe tool with tons of positive rake and a very small radius. I was striving for something similar to what 5Bears talks about on his web site for taking very fine precise cuts. I need to spend some more time on getting the shape exactly right. It cuts well, but I was not completely pleased with the surface finish, so something is not quite right there.

A second experiment I did involved trying some engine turning. I had gotten some Craytex abrasive cylinders off eBay. These are little rubber cylinders impregnated with grit that are supposed to be ideal for engine turning. I didn't fool with it very long because I could see the tool marks on my test piece where going to make it hard to appreciate the engine turned effect unless I could polish them out first. Need to get my surface grinder running!

The third experiment was by far the most successful of the three. I had purchased a set of corner rounding mills some time ago and wanted to try them out. They worked great and left a decent surface finish. These are just some no-name Asian imports I got off eBay. I didn't push them very hard, and the test subject was aluminum, but I think I'll be using them to make some trim pieces for my lathe enclosure rack, so stay tuned.

Are 2 Mills Better Than 1?

I picked up a second Industrial Hobbies mill over the weekend. A local fellow had it for sale quite cheaply, and I just needed to show up with a stack of 100's to relieve him of it. He had a great looking new Jet Bridgie clone, had been planning to convert the IH to CNC, but never got to it. He wanted to liberate some capital to work on a CNC router table (this guy is heavy into woodworking as a business), so I helped facilitate that for him. I'm not sure I really needed a second mill, but the price was right, and I figure this will let me work on the mill CNC conversion without having to tear down my happily working mill. I'll keep you posted on how that works out.

30 Taper ER 32 Collet Chuck

I recieved my El Cheapo 30 taper collet chuck from eBay today. The thing may turn out to have a half inch of runout or something for all I know, but it sure does look cool. It's dramatically more substantial and beefy than the R8 equivalent. I just wanted to have some piece of 30 taper tooling on hand to look at, and I only had to give $28 for this, so I bought it. Someday I hope to use it when I complete my belt drive with ISO 30 taper spindle for the mill.

I Blew Up My Power Feed

This stream of consciousness blog entry is getting a bit long because I'm combining stuff from two weekends and a bit more I should've written up sooner. Bear with me, this is my last entry.

I managed to strip a gear in my power feed for my mill. Calamity! I was so used to having the luxury of a power feed. I am not sure completely what the root cause of it all was, other than to say that the needle bearing fell apart and dropped the needles down into the bevel gears. These jammed and the motor proceeded to rip about an inch of teeth out of the nylon drive gear at the bottom of the feed. I shut it down immediately, but it was just too late and the gear was too delicate.

When I took it apart and saw what had happened, I briefly entertained making a new gear. Unfortunately, these are helical gears rather than straight spur gears, and are not at all easy to make. The project would be very time consuming, might not turn out well, and meanwhile I would be sorely missing my power feed.

So I ordered another one off eBay. They cost about $160. The first one I got was a total no-name Asian product, whereas my latest feed is an Asong. The Asong is noticeably better made than the original unit was and runs very smoothly. I am hopeful it will last longer!

In any event, I am back in business, everything in the shop is working well, so I am back to making progress on my project backlog.

1/13/07

Shop Air System

I took down the powered drawbar link from Current Projects and Doings (above) as it is finished and working well. In its place I have added a Shop Air link. I have a simple shop air system based around a Sears 2HP compressor, but I am planning to drastically upgrade it with a bigger compressor and a more permanent air distribution system.

1/2/07

Fabricated the X-Axis Home/Limit Switches for the CNC Lathe Conversion...

I am using two switches on each axis as combination home/limit switches. The X-axis (long axis on the lathe) is constructed using simple clamp-on brackets to hold roller microswitches:

X-Axis Home/Limit Switch

X-Axis Home/Limit Switch

The plan is to wire these switches in series in a normally closed configuration. If the limit is hit on any axis, the switch will open the series circuit. Likewise, if there is a connection problem, the system will fail open and the limit will be tripped.

 

Earlier Entries in the Blog...


Blog Archives

Index

Current

 

 

 

Featured Articles

Step-By-Step Guide to Making CNC Parts

CNC Router Cutter Types

Why Use a Single Flute Endmill?

Step and Servo Motor Sizing

The Truth About Tool Deflection

10 TIps for Router Aluminum Cutting

2 Tools for Calculating Cut Depth and Stepover

CNC Machine Hourly Rate Calculator

Special Purpose CNC Calculators

Feeds and Speeds Guide

CNC Cutter Guide

Feeds and Speeds By Material

G-Code Tutorial

  Feed Rate Calculator

Sales, and Special Deals

 

GCode is complicated.
G-Wizard Editor
makes it easy.

Try It!

 

Feeds and Speeds:
Made Easy.

Try G-Wizard

 

 

Do you want to be a better CNC'er in 37 Seconds?

Get Better Tool Life, Surface Finish, and Material Removal Rates Fast.

It's that easy. You can install and get results now.

 

Start Now, It's Free!