ARRRGH...Atlas Mk.2 popping out of direct drive ??...

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56type

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Here's the problem... Atlas 10100 Mk.2 set to it's lowest speed in direct drive and the drive pulley is backing away from the drive coupling ?? THE DRIVE COUPLING IS NOT MOVING, THE DRIVE PULLEY IS CLIMBING LEFT-TO-RIGHT AND DISENGAGING ITSELF FROM THE DRIVE COUPLING !!! The problem doesn't appear to be the drive coupling but rather the pulley assembly is backing away from it (drive coupling) under power.

Is there a spacer or other part missing ?? There seems to about 1/8" in. play/gap that's allowing the pulley assembly to climb away from the drive coupling... Here's a pic of the gap, also there seems to be a set screw on the gear assembly behind the drive pulley shown in the pic, should I loosen the set screw and try to move the gear back against the drive pulley to take up the slack or would I be screwing up an adjustment that I can't quite see due to the headstock housing covering the forward portion ?? The pic was taken with the drive coupling engaged for direct drive (pushed in to the right til it engaged the bosses on the pulley assembly) and the gap shown in the pic is how it is. Thanks...
 
The set screw isn't part of the gear. Its just a collar( I believe it just holds the "spindle back gear" on) The back gear is basically the only thing between the collar(with the set screw) and the spindle housing other than another key to marry the gear to the spindle. Inside that is the spindle bearing and housing. My 3950 had a shim in the gap you show, but it didn't take up ALL the slack. The parts book does NOT show any shim in there at all. I added another shim, now there are 2 shims, to take up most of the slack, but yet it still has minimal freeplay and it seems to work fine.
 
Yes I just checked mine (I have the ball-bearing version) and I have a gap too, but not enough to cause a problem-yet. The drive coupling is I think a weak point on these, the factory probably should have included a spacer to compensate for wear. Looks like you'll have to make one. Check the left hand end of the spindle- is the snap ring in place? Also is the little detent ball and spring in there? You'll need to take the coupling off to check.
There are two headstock versions for the MK2- the ball bearing version has a thicker spindle diameter at the left hand end and the couplers have different IDs, different part numbers; they are not interchangeable.
It could be that your backgear/collar is screwed in too far?- I don't see threads on my exposed section like your picture shows. Might want to check that.
Mark S.
 
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I just checked the factory drawing again, there are two snap rings: one outer and one just behind the coupling; make sure they are both there.
The gap you show is most likely due to wear on one or more of the gear faces, the factory didn't provide a way to adjust for that so you'll have fab something.
These lathes are not made for heavy duty use and the coupling system is a high wear point. The factory should have used two keys instead of one or some kind of spline arrangement but they were cutting costs. I ended up buying a whole 'nuther used headstock for mine because of shipping damage. Buying the parts from Clausing is too pricey. You could get a whole headstock for less than the price of the coupler and spindle.
Mark S.
 
My machine has the rollered Timken bearing in it according to a small sticker on the headstock cover. That's why I asked about bearing preload. Went to the local hardware store and picked up several "machine bushings" (as they were labeled), which were really 14ga. & 18ga. flat washers. Got two different I.D. sizes 3/4" & 7/8" in. to fit both the unthreaded and threaded portions of the spindle shaft. The 7/8" was a bit loose on the threaded portion and doubling up on the 7/8" made the shim too large to allow the drive pulley assembly to go back on and the snap ring to seat correctly.
What I wound up doing was taking one each of the 14ga. & 18ga. washers in 3/4" I.D. and opening up the I.D. from 3/4" to 7/8"in. and stacking them together. This took up the gap and allowed the drive pulley assembly to mount and the snap ring to seat and left zero play in the drive pulley assembly while sill allowing it to turn freely on the spindle shaft. I made a trial run cutting some 1" in. round stock and everything seems to be working as it should.
At some point I'll probably use the lathe to make a one-piece spacer to replace the "machine bushings" in there now for a cleaner look and possibly give it a bit more clearance.


I did mod the drive coupling by tapping it to accept a 6-32 x 1/8" in. set screw in the hole that contains the detent ball & spring. This allowed me to set the tension on the spring to compensate for any wear that may occur and to not have the spring and detent ball go flying off to parts unknown if I have to remove the drive coupling again at some point. Since the ball & spring are not under tension until the set screw is inserted and tightened down even with the outside surface of the drive coupling.
 
markba633csi said:
I just checked the factory drawing again, there are two snap rings: one outer and one just behind the coupling; make sure they are both there.
The gap you show is most likely due to wear on one or more of the gear faces, the factory didn't provide a way to adjust for that so you'll have fab something.
These lathes are not made for heavy duty use and the coupling system is a high wear point. The factory should have used two keys instead of one or some kind of spline arrangement but they were cutting costs. I ended up buying a whole 'nuther used headstock for mine because of shipping damage. Buying the parts from Clausing is too pricey. You could get a whole headstock for less than the price of the coupler and spindle.
Mark S.
Click to expand...

Yeah, I checked with Clausing while ordering a few other parts and the spindle assembly was 2/3 the price I paid for the lathe!! I think these Atlas lathes are still a bargain despite not being as heavy-duty as larger models, depending on what you're trying to do with it of course. Other than the astronomical price for replacement parts (though I confess I'm glad Clausing still supports these after all this time) it's a decent small lathe.
 
The Clausing prices for new parts are unfortunately typical of what the equivalent parts would cost for any roughly similar of the few machine parts still being made in the USA.
 
56: Sounds like you're going to be another resident MK2 expert in no time :D I spent lots of hours on mine, making brass gibs, freeing up the tailstock quill, lots of stuff.
I like your mod for the collar detent spring- great idea. I found also that the belt idler pulley wears the bushing out real fast- I bored mine and put a needle bearing in there, then made a new shaft from hardened steel. A little sae 30wt once in a while and no more wear and chattering.
A variable speed motor is a great addition to these lathes.
I wanted to add a second keyway to the coupler someday and make it live longer but I might just get a bigger machine- wouldn't mind a Logan or Sheldon!
Mark S.
 
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