# Tumbler gear replacement questions



## cdhknives (Mar 10, 2018)

I bought 3 new gears from Clausing about a month ago and was installing them today.  Some questions/issues are below.  Maybe I'm paranoid...but the perfectionist gene is pretty strong in my family!  Thanks in advance!

Both tumbler gears (20 and 24 tooth) and the spindle gear they mesh with were replaced:

1) The inner bushing/sleeve (forget the correct term) was a very tight fit into the new gears.  Is it normal that I had to press them in with a vise?  It wasn't particularly hard, but way too much for hand fit.  They basically fell out of the old gears.  I did not deburr anything and though after the fact that maybe the new gears had a bit of flashing...too late to check now.

2)  The only adjustment for gear mesh is the plate the tumber lock pin goes into, right?  I move it all the way up and still have this much slop in the gears.  Is there a better solution?






2A)  When set all the way up like that, the 24T gear is barely touching the spindle gear.  I can go past the standard detent hole and get this much mesh but the tumbler pin is in the top of the plate's slot:






3) The wear pattern on the new spindle gear looks poor to me.  Will this 'wear in' or is there another adjustment I need to use to get better gear to gear contact alignment?  This was not under load, basically just running to check fit and function...


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## cathead (Mar 10, 2018)

I agree that the lack of full meshing of the gear in the top photo is reason for concern(the one below the big gear).  
It's hard to tell from a photo but maybe the gear could be moved up by using some sort of eccentric bushing.  The 
wear pattern is not a big concern as they will wear in over time.  A press fit on the gear bushing makes sense to me.      
If the gear in question gets moved into place, maybe something could be adjusted to get it to move a bit more up.  
You mention a standard detent hole, maybe that could be repositioned for better fit of the gear.


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## wa5cab (Mar 10, 2018)

You don't want the bushing turning in the gear.  So the bushing should be a light press fit in the gear.

How much radial clearance is there between the new gears and the shoulder bolts that they run on?  I would have replaced them, too.  

How much vertical movement is there between the tumbler and the 10-1547 Stud?  Try rotating it 180 deg as most of the wear will be on the top.


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## cdhknives (Mar 10, 2018)

The inner bushing has anti-rotation ears.  It does not need a press fit to prevent rotation.  They have no real slop on the studs/shoulder bolts.


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## cdhknives (Mar 10, 2018)

cathead said:


> You mention a standard detent hole, maybe that could be repositioned for better fit of the gear.



This has already been done.  Moving it all the way ended up with what you see in the pics, and left the reverse direction literally not meshing in the standard position.  Running the tumbler down to the stops allows good meshing but there is no standard detent in that position, only the top of the adjustment slot.


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## cathead (Mar 10, 2018)

cdhknives said:


> This has already been done.  Moving it all the way ended up with what you see in the pics, and left the reverse direction literally not meshing in the standard position.  Running the tumbler down to the stops allows good meshing but there is no standard detent in that position, only the top of the adjustment slot.



Maybe look at the geometry of the parts and see what can be altered to move the gear where you want it.  If that's an idler gear, 
you could put in a gear with several more teeth...


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## jrkorman (Mar 11, 2018)

I've found that if relatively dry the bushings can be a hard fit. A couple drops of 30 wt oil and they go together fine.


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## Alittlerusty (Mar 11, 2018)

It appears that the 2 tumbler gears are different size . Shouldn’t they be the same size so when you reverse them the gear ratios remain the same


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## Asm109 (Mar 11, 2018)

They are idlers, they just change directions. No effect on ratios.


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## Alittlerusty (Mar 11, 2018)

In the first pic the 20 drives the 24 then the 24 drives the rest of the gear train and in the fourth pic the 20 drives nothing and the 24 is driven by the spindle and drives the rest of the gear train in the opposite direction so in my head the elimination of the 20 definitely changes the ratio as well as direction of the rest of the gear train but I’m not fully coffeed up yet.


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## Alittlerusty (Mar 11, 2018)

I’m just wondering if someone changed the size of one of the gears to cut a special thread


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## cdhknives (Mar 11, 2018)

Alittlerusty said:


> I’m just wondering if someone changed the size of one of the gears to cut a special thread


I have only cut 'normal' threads and the QCGB is correct.  The gears also match the Atlas parts list.  The 24T gear runs the saddle L->R which is opposite normal threading and the 20T is engaged for L<-R.


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## Asm109 (Mar 11, 2018)

In one direction the power runs through one of the idlers on the arm.  Output gear turns same direction as input gear.
Flip the arm to the other direction and the power runs from input gear to one idler then to the other idler then to the output gear.
Output gear turns opposite direction of input gear.


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## Alittlerusty (Mar 11, 2018)

Assuming a 48 tooth spindle gear in either position other than center, one revolution of spindle turns the 24 tooth gear 2 revolutions. Got it. Did u compare the diameter of the new gears to the old?


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## RJSakowski (Mar 11, 2018)

Alittlerusty said:


> In the first pic the 20 drives the 24 then the 24 drives the rest of the gear train and in the fourth pic the 20 drives nothing and the 24 is driven by the spindle and drives the rest of the gear train in the opposite direction so in my head the elimination of the 20 definitely changes the ratio as well as direction of the rest of the gear train but I’m not fully coffeed up yet.


If there are n teeth on the driving gear and m teeth on the driven gear, the ratio would be 20/n x 24/20 x m/24 in the first case and  24/n x m/24 in the second case.  In either case, the overall ratio is m/n.


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## RJSakowski (Mar 11, 2018)

It looks like the detent plate in photos 2 & 3 still has some adjustment.  Have you tried adjusting that?  If you are at the end of the adjustment and clearance is still excessive, the tumbler detent pin may be worn or the spring weak.  Either of those conditions would increase the tooth clearance.  If that was not the cause.  It looks like you can increase the travel of the detent by filing the slot longer.  Barring that,  I would just make a new detent mechanism with the holes moved slightly upward.  

When I added a reversing tumbler to my 602, I set the tumble for the proper tooth clearance and marked the position of the tumbler.  Then I drilled the detent holes.


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## cdhknives (Mar 11, 2018)

The picture of the detent plate has it jammed to its stops.  The end of the plate bottoms out before the groove.  I could remake it or grind the end off.  Right now if I get it just about perfectly centered the bottom of the slots acts like a second detent hole and the gears mesh better...but the detent pin does not appear to be fully engaged so I worry it will pop out at a bad time and ruin a threading project.  I am still studying it.  Different screws and a countersink might help too.


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## wa5cab (Mar 17, 2018)

To reiterate the subject of spur gear trains, if you have two parallel shafts each with a spur gear on it, regardless of how many other gears you might put between them, so long as all gears are in the same plane, the overall ratio of the assembly is the ratio of the first and last gears (in this case the 32T spindle bear and either the screw gear (change gear lathes) or the first gear inside the gear box (32T input gear of Atlas QCGB).  The only way that you can change the input to output ratio is to introduce one or more compound gears (two gears on a common axis with one driven and the other driving).


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## BtoVin83 (Mar 17, 2018)

Just throwing it out there but is the detent plate upside own


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