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Scoring damage on bearing bore seat

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5ubtle

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#1
I found some scoring damage on the bearing seat for the upper bearing on my mill's spindle. The bearing is a 6006, so this OD is 30mm. I believe that the raised portions are raised about 0.003" (just a guess. I can feel them with my fingertip). I expect that this could be cleaned up with a honing stone of some type, but I've never done this before, and don't have a honing stone.

Do you have experience fixing similar damage? What is a good way to fix this?

DSCF5373b, Scoring on upper bearing seat of spindle.jpg
 

Latinrascalrg1

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#2
Check out this video, should be what you're looking for using a Loctite Metal repair paste.
 

P. Waller

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#3
Yes, file it off, this almost certainly happened during the original assembly.

If this is a 30,000 + RPM spindle you may want to look for advice elsewhere, if a typical 3000 RPM hobby machine spindle ignore it.
If as a hobbyist you are truly concerned about this sort of thing replace the spindle.
 

benmychree

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#4
This damage would sem to indicate that the bearing fit is too loose on the shaft, and the shaft has been spinning in the bearing inner race; the damage to be seen would have not been done at assembly, if so the burrs would be parallel with the shaft, not circumfrential as seen in the pics; yes, lightly file them off, and assemble the bearing with a little dab of Loctite.
 

GL

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#5
Loctite in this case would be the bearing mount type, not the thread locker type. Fills in the gaps and locks the race to the shaft.
 

Latinrascalrg1

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#6
Correct! The method i recommend uses the loctite surface repair epoxy with metal filler that is machine-able and should tighten up that loose race surface so this doesn't happen again if done correctly.
 

5ubtle

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#7
Thank you for the replies.

This is a 3,000 rpm spindle, so nothing exotic. Replacing the spindle is not really an option since the machine is 53 years old. Pictures of the machine are here.

Obviously, I am not an expect on this topic, so take these opinions as just my guesses.

I believe that the scoring was causing during assembly and not due to the shaft spinning in the inner race. I have two reasons for this. 1) The scoring does not go all the way around the circumference. The scoring covers only about 240 degrees of the circumference. 2) The score marks appear to me to indicate that metal was displaced along the length of the spindle (instead of around the circumference of the bearing seat). My camera is not able to capture the fine detail which suggests this.

After making some measurements, I believe that the high points (which stand proud of the normal surface) are only about 0.0002" high. I realized that I do have a fine stone for knife sharpening and my plan is use it hone down the high spots. After honing, the bearing seat should be within 0.0001" of 30mm. I will check the press fit and then decide if I need Loctite. Maybe it's not even worth the time to stone it.

DSCF5378.JPG
 

Cadillac

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#8
My opinion is the marks were made on assembly. So when they went to press bearing it went on crooked then with a little more pressure it straightened out. They would of had a spacer to span the spindle to press so everything wasn’t aligned before mounting bearing. Ive had this happen to me when juggling spacers and so to press bearings. I just use a fine stone and take burr off then polish with some emery. A little dab of Loctite won’t hurt anything.
 
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