How tight should the Bull gear be

kvt

kvt

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Ok, working on the lathe, but need to know how tight should the bull gear be on the spindle. When I took it apart I had to use the shop press tp press the spindle out of the bull gear while still in the head. But now I have my new bearings and seals. But even after cleaning up the spindle and the bull gear, it is so tight that I am unable to get the bull gear to slid onto the spindle shaft after freezing the spindle and a little heat of the bull gear. I verified that the key way in the bull gear and on the spindle are not what is causing the problems with assembly.
So how tight should the bull gear be on the spindle. An old 1977 model of a Taiwanese made lathe.
any suggestions, experiences etc. No where have I read that it should be that hard to get the bull gear on and off, as you have to remove the spindle to change the belt.
 
If your bull gear is keyed and then held in position with a set screw, there is no reason I can think of for it to be that tight. I am just thinking about the lathes that I've had apart, but they might be completely different. If it does have the set screw and the spindle is not galled up keeping it from sliding on, I would work on the bore of the gear until it's a tight slip fit.
 
No set screw on the bull gear, One side sits against a edge on the spindle and the other side is against the pulley set up, which is held in place by a collar with a set screw.
Ken
 
This might be completely wrong but were it mine I would chuck up the bull gear and polish the bore until I got a fit I could work with. It sounds like it's captured by the cone pulley so there shouldn't be any worry about lateral movement.
 
When working on my lathe the bull gear was a very tight slip fit.
Had to use a bar on each side to wedge it off it's fit and was later able to knock the spindle back into it with a large rubber mallet.
Just be careful not to pound a bearing or damage any shoulders on the spindle.
I did lightly polish the spindle and the bore of the bull gear before assembly to make it easyer.
I tested by assembling on the bench before installing it innto the headsto
Have had no problems.
Because of the dimensions of the bull gear, heating it could cause the material to swell into the boar, making assembly harder.
Dry ice packed into the spindle and a super thin coat ( so thin it might not be vizable ) of graphite or nickle antisieze rubbed in the bore and on the fit
will help.
Keeping the gear square to the spindle is critical
 
Thanks, Also tried at room temp with a frozen spindle, Lets put it this way to pop it out took the 20ton press a bit, I found a few gall marks on both the bull gear that I polished out but still not sliding on even with a fair amount of force. I did notice that it looked like at some point the key may have split as there is a real ruff spot on one side of the keyway in the bull gear. The only time I have seen that on a pulley was when a key sheared off. I have no other lathe large enough to grab the bull gear so that I could clean it up that way. Did what I could with piece of round stock and fine emery cloth.
Will keep working at it. Thanks for the info everyone.
 
Have you measured the OD of the spindle and the ID of the gear? I'd be interested to know what kind of interference you're dealing with.
 
I agree with Chuck K. Measure in multiple areas for dimension, roundness, and any high spots from galling.
Since the gear is keyed it shouldn't need more than a light press fit.
If the key was once started off axis, it could have caused the galling you described.
 
Ken,

If it's any help, the bull gear on my 14" Rockwell lathe and the 13" Sheldon lathe are a slip fit to the spindle. About .0005" to .0015" loose. Both held in place with a key and and a bearing take up nut.

I agree, that's too much interference fit. No more than .0005" Any more than that, yeah, a 20 ton press is needed.

Even on much larger lathes I've worked on many years ago, the bull gears were never press fit on the spindle. They were heck getting off though!

Ken
 
Do not have a a 1 to 2 or a 2-3 mike so doing this with a calipers, 2.040 on a frozen shaft, and 2.03o for the hole on the bull gear.
Back side of the Bull is against a step in the spindle the other side is the pulley which is also at a step to keep it pushing into the bull gear.
The other end of the pulley assembly is a spacer collar with a set screw to hold it.

spindle.jpg
 
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