Atlas MFC Mill - Rebuild/drawbar ?

After much procrastination, I finally got around to finishing the rebuild on a Atlas MFC horizontal mill that I purchased several years ago. Now that It's back togetrher and running, I noticed that the arbor is threaded on one end. Is this for a drawbar ? If so, does anybody have a drawing for one ?

Thanks,

BW

Reply to
BW
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Yes it is for the drawbar.

Mine is an origonal but making a duplicate would not be hard. Actually I have to repair mine as the previous owner damaged it by crossthreading it into a morse collet.

I will post some deminsions this evening as my MFC is at work.

Hugh

Reply to
Hugh Prescott

It *should* be threaded on *both* ends. a female thread at the end which fits into the mill spindle to accept the drawbar, and a male thread on the other end for the nut which clamps the stack of spacers and cutters onto the arbor. There should also be provisions for a bearing to support the outboard end. This bearing point may protrude past the stack clamp nut, or it may be a bearing sleeve which is part of the stack, depending on the particular mill and its overarm. (This above is presuming an arbor for the standard side milling cutters (which look like fat circular saw blades). If you have an end-mill holder, or a stub arbor, this may not apply.

My experience is on a Nichols horizontal "hand miller" (lever feed in X-axis -- with optional leadscrew X-axis feed), which is somewhat larger than what you have, I believe. Isn't your Atlas a benchtop machine? The only Atlas horizontal millers which I have seen were.

A drawbar is not difficult to make. It can even be made with some allthread, a couple of nuts (to lock together), and (perhaps) a shoulder washer to fit the allthread to the ID of the spindle so it runs on center.

Mine came with a drawbar which someone had made by threading both ends of some steel rod, putting a nut onto the end away from the arbor, and welding it at the right position to allow proper lock-up. However -- there are two different drawbar threads on 40 taper arbors, and when using a 30-taper end mill holder in an adaptor sleeve, you need yet another thread -- plus a perhaps little more length. I made the second drawbar from allthread and a pair of nuts locked together to define the bar's length. That has worked quite well for me.

I would advise about a 30-45 degree taper on the end of the rod to make the drawbar easier to start into the arbor or end-mill holder.

When I got the vertical head for my Nichols mill, it had an interesting drawbar. The bar was threaded a different thread on each end, to match one or the other of the standard 40-taper threads, and the nut was a cylinder with a pair of opposed wrench flats, and drilled and tapped at each end for the two threads. So -- to change from one thread of arbor to the other, you simply disassemble the drawbar, and turn both the nut and the bar end for end, and reassemble. You *could* consider it to be removing the nut from the end of the drawbar, and moving it to the other end and screwing it back on, and *then* turning the assembly end for end.

But basically, a drawbar is not rocket science. All it needs is a thread at one end to match the arbor, and something at the other end which won't go down into the spindle so it can exert a pull on the arbor to fix it firmly into the spindle.

Make one using the right size of allthread so you can determine the proper position of the nut. Once you get that right, you can (if you so desire) make a nicer drawbar by single-point threading the appropriate diameter bar in your lathe, and turning up a proper nut to fit the outer end (whose thread need not match that at the arbor end). While you've got the allthread one, use it to hold the arbor and cutter while you cut wrench flats on the nut which you just made. You might wish to use loctite (or a weld bead) to make the assembly of the nut to the drawbar permanent, if you don't need to make a dual-thread one like I described.

I have also seen drawings (in _Machinery's Handbook_ of drawbars with two threads on the same end, but I don't remember whether the assumption was that the smaller thread would reach more deeply into the proper arbor, or that there may have been adjustment at the nut end.

Enjoy, DoN.

Reply to
DoN. Nichols

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