# Threading, Atlas/clausing Mk2



## T Bredehoft (Jun 24, 2016)

OK, I need help. I'm trying to make an ER40 collet holder to screw on the spindle. I'm to the point of chasing 1" x 10 threads. The first three passes were OK, then things started going wrong. I finally realized that the lead screw was shifting to the right as I engaged the half nut, giving me multiple tracks. 
So. I moved it all the way to the right (it won't shift any more) and the gears are enough out of alignment that they wobble and vibrate, threatening to jump apart. 

This thread is scrap, I can reverse the piece of material and start over at the other end, but if I can't depend on the lathe, what's the point?

Is there a way I can pin the lead screw at the left end of it's travel?  put a dowel pin in it? or is there something I'm missing.  At one time I spent 8 hrs a day chasing threads for a living, so its' not me.


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## wa5cab (Jun 24, 2016)

Tom,

This reply was in error and applied to 10" and 12" but not to 6".


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## T Bredehoft (Jun 24, 2016)

I thought that would solve my problem, went to adjust it, found that there is no shoulder at the end of the thread, it won't seat against the support. Or did I misunderstand you?




*UPDATE*

I figured out what I'm doing wrong.  I'm threading internal threads, run the spindle backwards, cut on the back, back the tool out. The lead screw is not supported for that option. Guess I'll hve to cut the threads blind.


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## wa5cab (Jun 24, 2016)

Hmmm.  Well, live and learn.  They did do it differently on the 6".  If you will look at Page 15 of the 10100-01 manual, #4 is the lead screw and collar assembly.  #19 and 18 are another collar and set screw.  The position of #19 will determine how far the lead screw and gear can move to the left.  Either the collar on #4 or the shoulder on the right end of the lead screw will determine how far to the right it can move.  According to the drawing, the collar on the left end of the lead screw is larger in diameter than the hole through the change gear bracket.  So if it takes the thrust from the threading operation, it would be rubbing on the bracket.  Which doesn't seem a good idea.

However, it may be that one of the two collars are out of their proper location.  If the lead screw needs to move to the right (as in your photo above) in order for the screw gear to mesh properly with the gear driving it, then you need to adjust collar #19.


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## mattthemuppet2 (Jun 24, 2016)

on my mk1, there's a collar between the banjo and the leadscrew support and another collar on the other side of the left leadscrew support. The one under the banjo should be pinned (a previous OP drilled mine out and replaced it with a set screw) and the other one has a set screw. You need to make sure they are both snug up against the leadscrew support without binding, then you're good to go.

I had the same issue cutting a LH thread away from the chuck and doing the above stopped it happening. You can quickly check by engaging the halfnuts and then trying to move the carriage back and forwards. it shouldn't 

You can also cut those threads towards the chuck if you cut a relief groove at the end for the tool to stop in. That's what I did when I made my ER25 collet chuck. I also worked out the change gears for various metric threads (tried 0.5 and 1.0) which I can send you or I can dig out the program I used (nthreadsb or something similar).


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## T Bredehoft (Jun 24, 2016)

Matt, I found in the Manual the set up for cutting Metric threads, they call out the gears, just like for normal American threads. 

P 15, manual, shows the gear end of the lead screw, No. 19 is the last piece in the train away from the gears, it's a collar.  (L2-682).  On page 14, det 10 (M6-16) Feed Screw Bearing is shown, but the feed screw and any bushing is absent.  The 'bearing' has an as cast end on its' left end. if I made a bushing to press against it, I'd have to machine it to keep from tearing the bushing up. 

Nowhere is the left end bearing called out, although part of it can be seen in the illustration, lower right on page 13 of the assembled gears and head.


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## mattthemuppet2 (Jun 24, 2016)

neat, I'd missed or forgotten about that for some reason, RTFM! Still, wouldn't have helped with the 0.5mm pitch threads as those need an extra position.

I don't have the Mk2 manual to hand, sorry, just telling you what it looks like on the Mk1.


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## wa5cab (Jun 24, 2016)

Tom,

Item 17 on page 15 in the 10100 manual is the left bearing.  It is the whole casting.  The externally visible collar is Item 19 on that page.  If the collar shown drawn on the lead screw on Page 15 is pinned to the lead screw, then the end float adjustment is made by, with the gear cover off, pushing and holding the lead screw toward the tailstock.  Slip a slotted sheet of 20# typing paper between the Item 17 casting (left bearing) and the collar #19.  Slide #19 lightly against #17 and tighten the set screw.  Pull out the paper and squirt some oil in there.


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## T Bredehoft (Jun 26, 2016)

Continuing update....

Back to chasing the 1" 10 internal threads.  I've been having problems....
"Who will rid me of this troublesome Lathe?" to paraphrase Henry VIII.
 I got all set up to chase the threads, made four passes, everything working peachy.  then the bearing on the left end of the feed/lead screw bound up, seized up tight. 
I walked away for the rest of the day, came back this morning, disassembled the gear train, removed the lead screw, filed the buggers off of where it had galled. and put it back together. Lots of Oil and Wheel Bearing Grease in the appropriate places. I've tried four times to pick up the thread, you can see each one clearly. 



I've done this before, but not for 20 years. What's changed since then? how do I pick up my threads so I can make one groove?  

I don't really expect an answer, but if someone had solved this problem, I'll be glad to accept advice.

I'm certain that it can be done, put the tool in the farthest in groove and continue, but you can see what's going on, apparently there is some slack I'm not considering.


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## T Bredehoft (Jun 26, 2016)

*Success*

No Pix, I'm ashamed of the threads, but they screw onto the arbor with no shake.  The crests are a bit ragged, though.  Now to make it into an ER 40 collet holder.


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