Draw Bar For Atlas Mill

[JPMacG]

I dropped and lost the bushing for the draw bar on my Atlas mill. I mean the bushing with a through hole for the draw bar shaft and a taper at the end that contacts the spindle. I spent 3 hours on my hands and knees looking for it. I took the change-o-matic assembly off and looked everywhere inside. It has vanished. I think it fell through a worm hole into a parallel anti-matter universe and is being tossed around by Schroedinger's cat.

Can anyone point me to a drawing of the bushing? I just need its overall length and the length of the taper.

Thanks

 

[wrat]

It's nothing so fantastic as a wormhole or a tear in the space-time continuum. You've just encountered steel that is "concrete soluble".

Because of some mechanical or machining quality that i don't understand, it seems most small screws are made of this material, in that when it hits the floor, they instantly dissolve into the concrete without even leaving a stain. Usually after 2 or 3 bounces.

This may be among the larger parts made of such steel. But it's certainly not impossible. I've heard of remarkably large parts suffering the same fate.

Wrat

 

[wa5cab]

Mine isn't accessible (buttoned up in a crate with the mill). All that I came up with is this verbal description:

******************************
All I have to measure it with is a steel rule and a vernier caliper, so these aren't
precise measurements but they should be close enough. The draw bar is 10-11/16" in
overall length. With the bearing removed, the distance from the shoulder to the end
of the threads is 6-11/16". The bearing is 1-1/8" long, so the distance from the end
of the bearing shoulder to the end of the threads is 5-9/16". Let me know if you need
more dimensions.

VSAncona
******************************

This does not match the one reverse engineered Draw Bar drawing we have that shows the length of the 3/8" diameter part as being 6-5/16" instead of 6-11/16".

A quick and dirty way to determine a length that will work is to seat something (preferable something short like a milling cutter holder) in the spindle taper. Stick the draw bar through the spindle and hold it against the holder, and measure the clearance. Subtract about 3/8" and make the bearing that length. If you are going to bevel the bearing, the bevel is 45 degrees and the small end should be about 7/16" diameter. I don't like the tapered bearings and always use a 1/8" long step with an OD just under the spindle bore diameter. The tapered bearing takes two hands. The stepped one only one, with the other hand free to hold the item being installed.

 

[kd4gij]

It is them pesky shop gremlins I tell ya. Just wait, when you get a new one made thy will return it.

 

[JPMacG]

Thank you everyone. I will do the measurement that WA5CAB described to get the length. I'll try to post a sketch for the next time the question comes up.

 

[Mondo]

I think a simpler solution is to clean the shop, especially the floor. Reach around at floor level under cabinets and benches with a magnet on a stick or telescopic handle. That magical tool will drag out anything magnetic, often with other non-magnetic debris that gets tangled with the chips!

Spiral_Chips

 

[JPMacG]

I went ahead and made a replacement bushing out of some free cutting brass stock that I had left over from another project. In order to engage three or four threads on my collets I had to shorten the bushing to about 0.6 inches. This length does not match the length given by VSAncona (above) nor does it appear to match photos that I have seen here and on eBay.

So I'm thinking that my draw bar is not the original Atlas part but was home made by a previous owner of the mill. It does have the square drive and looks like the Atlas part, other than the shoulder being closer to the threads. Nevertheless, it works.

Now that I have made a replacement bushing, I expect to find the lost bushing in some completely obvious place any day now.

 

[mattthemuppet2]

I'm surprised you didn't find it the instant you finished the replacement! Good job on the replacement though

 

[Harley80]

I have to make the whole drawbar. It was missing when I got my mill. A made the 1” arbor already but still have to fab the spacers. Looking for some heavy wall tubing to start with.

 

[Bi11Hudson]

I have to make the whole drawbar. It was missing when I got my mill. A made the 1” arbor already but still have to fab the spacers. Looking for some heavy wall tubing to start with.

The drawbar on my MF-C is threaded for 3/8-16 as a solid. The taper is cut on the end of the drawbar shaft, there was no bushing. I do a number of shenanigans with the mill, some based on end mill holders for milling cutters from a vertical mill. Of these end mill holders, some are threaded for 3/8-16, some for M10-1.25. (I think, it may be M10-1.5) In any event, the M10 all-thread I use is non-plated stock from a supply house. If I am using all-thread, either one, I made a thick brass washer with no taper and a nut to fit the particular drawbar. It isn't like I am jerry-rigging anything on the mill, just using unconventional assemblies. I saw no need for using a hollow tube, there is nothing I run that requires it. The all thread serves to hold the mandrel in place, that's its' only function on either milling machine.

.