Another Atlas 12x36 Acquisition

[wa5cab]

Ryan,

Although 3AT and 3C collets normally come in 1/32" increments and 3AT at least can be found in 1/64" increments, 2MT and 3MT collets commonly come in 1/16" increments. So decide what milling cutter and drill diameters you need and buy them with 1/16" increment shanks (and you will need to use single-ended milling cutters). Not much that you can do about drill bits below 1/4" except to use a headstock drill chuck. Buy 3MT collets with 3/8"-16 drawbar threads to fit the cutters.

1. I would buy one, myself, as I have other things I need to do. But...

2. Make the draw bar out of 3/8" round stock, not hex stock. It needs to be round at least on both ends, round stock is cheaper than hex, and there is no benefit to having it hex in the middle anyway. Cut the threads with a die nut. You only need about 3/4" threaded on the collet end. If you can borrow a tailstock die nut holder, you can use that and be able to say you did it on the lathe (in back gear). The Atlas has no brake, so if you try to thread the rod with a single point tool, you would probably need to cut a relief groove for the cutter runout or the main practice you would get would be in checking your blood pressure.

3. You could make the rod out of all thread but if you are going to make a drawbar, you may as well make it look decent. And you will be less likely to bend the solid rod than the all thread. Do not use a hex nut and wrench. If you do, you will soon come to hate it. And the first time that you forget and leave the wrench on the nut and turn on the motor, you will really hate it. Plus, you have to have something on the left end to hit when you want to remove the collet from the spindle (I use a piece of 2X4 oak block about 6" long.

Put a handwheel on the left end. Diameter between 2-3/4" (factory) and 3-1/2" (an aftermarket drawbar that I have). The left face of the handwheel should be approximately in the plane of the left vertical face of the gear cover up to an inch or so to the right of that. Between the left face of the spindle and the right face of the handwheel hub you need a spacer/thrust bearing. OD 1" to 1-1/4". ID 3/8". Length depends on design of the handwheel. Turn about 1/8" of the right end of the spacer down to a diameter of about 3/4" so that it is a slip fit into the spindle bore. This centers the drawbar in the spindle. You will see some spacers (including factory ones) for both drawbars and drawtubes that are beveled on the end instead of having a reduced diameter pilot. The latter works better all around, both when hooking up and tightening the collet, and when removing it from the spindle. With the beveled spacer, releasing the collet is a two hand operation. After looseining the hand wheel about two turns, you need to hold the beveled spacer into the slight countersink in the left end of the spindle while you hit the handle (and the knuckle of your right index finger) with a block or something. The piloted spacer will stay in place all by itself.

The length from the face on the left end of the spindle to the right end of the rod should be between 8-1/4" and 8-3/8". So the total rod length needs to be that plus an amount that will vary depending upon handwheel design.

Robert D.

 

[Smudgemo]

I finally got a chance to pick up the milling attachment. I can't say for sure, but it looks like new.


As for mitering tubes, this is the idea:


I ran a scrap tube through it just to see what would happen, and it appears to be successful. Setting angles will be fairly easy. I think the thing I'll need to figure out is how fast to run the cutter and what feed-rate works best with this thin-wall tubing.

 

[wa5cab]

Yes, the milling attachment does look like it's had little to no use.

I would expect that Milwaukee has a web site. Try that for a recommended RPM chart. Or some of the other vendors. That's a good idea to use a hole saw for that operation. I sometimes use them for rapid diameter reduction on short workpieces that are going to have a hole through them anyway.

Robert D.

 

[Smudgemo]

Hey Robert,

Something along the lines of this?


It's been a few years since I last cut threads, and using a length of drill rod didn't make the job any easier. But they seem to be acceptable and do indeed hold the collets. I made the relief because it greatly simplifies the process.



I added a thrust washer and went with a cone shape for the centering part. A set-screw holds against a ground flat on the rod, and I left it a bit long to have something to tap against to release the tool.



This is one job I won't miss doing by hand. Slitting the ends of the forks or seat/chain stays for bikes with a hacksaw and files so the dropout fits snugly for brazing (this is just a scrap tube), and doing it at a 5-10* angle so you don't need to bend anything isn't easy.


I'm thinking of adding a snap-ring to hold the cone and washer in place, but I'm not sure how I'd cut a thin groove. I must say that using the lathe to make a part for itself is pretty cool.

-Ryan

 

[wa5cab]

Ryan,

Yes. That looks like a pretty typical drawbar. Except that I would have to cut off the rod flush with the left end of the handwheel. Sooner or later, I would forget and reach around with my left hand to smack the handwheel to release the collet and put a bloody D-hole in my left palm. :-( Once you are satisfied with the thread engagement in the collets, I would drill and pin the rod to the wheel. And not depend upon the set screw. Or alternatively groove the rod for a circlip.

As far as a tool to make circlip grooves, I have for years used a grooving and cutoff tool made by Kaiser Tool Co. They call it "Thinbit". The tool holders come in various square sizes. I use 3/8" square holders as that's what fits my QC holders. The cutters mount in the end of the holders somewhat like replacable insert carbide tooling. but on the side instead of the top. The cutters come in various widths and lengths. For grooving you would use the shortest length and for small circlips the 0.029" wide one would probably work OK. I forget what other widths they come in. I use short or long 0.062" ones for parting off. The short ones for tubing and the longer ones for solid. They aren't what I would call particularly expensive. Aside from choice of left hand or right hand, one tool holder fits the entire range of cutters. So you could get by with only one holder if you don't mind the time it takes to change cutters. The holders come in left hand and right hand Unless you run it into the chuck, a holder should last forever. Breaking off a cutter won't generally damage the holder (I've broken a few). The tools are also useful for making O-ring grooves.

Robert D.