Looking for (constructive) recommendations

R

rficalora

H-M Supporter - Silver Member
H-M Supporter - Silver Member
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Dec 23, 2020
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Go easy on me; I am a newbie. I am not a machinist, but am working to learn.

Right now, I am trying to clean up and functionally restore a lathe I recently bought and I have an issue with one of the shafts in the gearbox.

This is the main input shaft to the gearbox. I assume it should spin freely and smoothly when fully seated but it gets tight. In the video below, I insert it to about 3/32" from fully in. If I go further, I can't turn it by hand without putting the drive gear on to get more leverage.


I'm considering chucking/spinning it in the lathe and using some emery paper to clean up the shaft.

Am I right that it should rotate freely/smoothly?

Assuming so, what are your thoughts about whether using emery paper would address the issue? Or, would you recommend a different solution?
 
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I agree it should turn freely. I would check for burrs in the bosses and shaft, check the shaft for a slight bend.
 
I'm also a complete newbie so don't laugh if this is all wrong :)
Maybe dykem or felt pen the shaft to see where the high point is as a start?
 
First, clean the bearing surfaces of the housing and shaft. Apply oil to both surfaces and see if that helps.

Do you have a dial indicator? If yes, put the shaft in as far as it will go and still turn by hand. Then use the dial indicator to see if the input end of the shaft is running true. If the reading is changing more than a couple of thousandths, the shaft is bent.

If the shaft isn't bent, polish the input shaft where it runs in the housing, but very little. You want to smooth it, but not reduce the diameter of the shaft.

Then report back.
 
It looks like it is not straight.

If the outside bearing has shifted it causes the shaft to not properly align with other end.

It could have moved when torn down.

Look closely as it goes into second bearing.

You may gently tap the shaft with a chunk of 2x4 to see if it lines up better.

Sent from my SM-G781V using Tapatalk
 
Ok, I have it running smoother, but I believe, based on this, the shaft is bent. This is with the end of the shaft just before going into the 2nd hole.


But, by running some 320 emory paper over it for a few seconds it is running smoother.


It does not spin freely but does not have a lot of resistance either.

Next steps?

I assume I will need to make a new shaft. Correct? Or can it be straightened?

If it needs to be re-made, can I use this shaft as it is to reassemble the lathe to do that (I have a mill to cut the key slots).
 
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Glad that you are making progress.

Now insert it fully and check the input end of the shaft for runout with your indicator.
 
Looks like only about 6-7 thousanths bent. Borderline usable. Take all the measurements of it and plan on making a replacement. You probably could make a replacement now without the gearbox in fact if the rest of the lathe is up and running
You could try straightening it also
 
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