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How bad is this SB 10L head stock bearing

Gard

Aluminum
Joined
Mar 18, 2016
Working on rebuilding this lathe. I checked the headstock bearing by the book. Pulled up on a shaft thru the headstock with 75 lb and measure spindle movement, I got 0.0020" play on the front and 0.0013" on the back. This is pretty close to what is recommended so I figured it was in good shape. Took the bearing caps off. This older lathe has the segmented iron bearings with some significant scoring. I attached a dial indicator to the carriage and see most of the scratches are less than 0.0003" deep, there are 2 narrow bands that are 0.002" deep. There are a couple of corresponding small lumps on the spindle I stoned off after taking the photo.

My thoughts are to reinstall the spindle without caps, turn it on and polish the spindle with a very fine stone. Than use a flexible cylinder hone on the insides of the bearing after installing the caps. Not trying to get all surfaces perfect just get the high points off. Disassemble and clean everything. Install new felts and adjust bearing play. Any opinions?

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john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
Unfortunately ,every hit with abrasive is less metal and more wear.....id polish the journal with something like the tape crank grinders use to polish cranks....I think youd be better served removing any loose metal from the bearing with a fine wire brush and maybe a pointed scraper.....if you use a hone there ,you will never remove all the loose abrasive.
 

Gard

Aluminum
Joined
Mar 18, 2016
Thanks, I am not familiar with tape crank grinders what does that material look like? I tried removing that lump with a scraper and it was welded on there pretty good. I don't think a wire brush would of had any effect. Perhaps I should of just left it there and let it ride in the grove it had created? Too late now, its all polished off (I used a very fine stone) without removing any of the surrounding crank.
The shims I removed are 0.0215 and 0.0255 on the chuck side and 0.031 and 0.0315 on the gear side. I will get some measurements but I think a light stoning will remove less than 0.001". I am also concerned about grit trapped in there. The headstock will be removed (so I can get at the gear box), stripped and thoroughly cleaned in multiple passes of diesel and gasoline with stiff brush and compressed air. Perhaps final clean with detergent. Probably makes sense to paint before reassembly.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
The tape is an abrasive material about 1 " wide on a roll ...Id think someone like 3M would make it .....I suspect its about 1200 grit......if there is nasty steel welded to the surface,then a coarser abrasive may be needed.
 

JST

Diamond
Joined
Jun 16, 2001
Location
St Louis
Unless there is real material transfer, the "scoring" may not be any problem at all.

I've always been told to leave the bearings in their present condition unless there is a real issue. They "ran-in" like that, and will continue to work.
 

Gard

Aluminum
Joined
Mar 18, 2016
Unless there is real material transfer, the "scoring" may not be any problem at all.

I've always been told to leave the bearings in their present condition unless there is a real issue. They "ran-in" like that, and will continue to work.
Thanks for the comments, in my photos you can see some lumps of material that were transferred from the bearing to the spindle, these seemed pretty high but I did not measure them before stoning them off. The bearing clearance was only 0.002" which is not too bad so perhaps I should of left them alone. I had only used the lathe for an hour or so before I started fixing various things and one thing led to another... So I do not know if there was a real issue with the HS bearings. I certainty did not notice any weird noise, smell or heat.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
I would make sure the pieces embedded in the spindle were not loose and likely to do further damage ...probably try to pry them out with a sharp tool like a small chisel ,or screwdriver sharpened to a edge,then give the spindle a polish with very fine grit paper .
 

jim rozen

Diamond
Joined
Feb 26, 2004
Location
peekskill, NY
" So I do not know if there was a real issue with the HS bearings. I certainty did not notice any weird noise, smell or heat."

Possibly a solution in search of a problem...
 








 
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