SB 13 bearing nightmare?

I recently bought a nice looking 13 and have used it a couple of times. Tonight I decided to check the bearing clearance. The large bearing was about right but the rear had over .002 per the book procedure. As I disassembled it, I was surprised that the bearing cap bolts were no more than finger tight. When I took the cap off, there was a collection of hand cut brass shims along with some small pieces of other shim stock thrown in. So I took the large bearing cap off and found the same thing. Not good. If the small bearing cap is tightened, the spindle gets very tight. The spindle bearing surface looks Ok from what I can see. It is not an old lathe, about 1984 I think, the rest of it appears to be in good condition.

What do I do now? Cut myself some more homemade shims? Buy new replacement shims? Sell it on Ebay? Go to sleep and forget the whole thing?

Can one just order up new bearing shells and start again? According to my old parts book these came as a set with expanders, wicks, and shims. Can this be done by the reasonably talented amateur, or are specialized honing and fitting skill required? How thick is the shim stack normally? The collection of scraps in mine is around .009 each side on the small bearing.

I don't mind spending the money for new bearing shells if that is the way to go (and they are available).

Any help from the experts woudl be appreciated!

HI There,

If you have read the procedure for bearing adjustment, you know that shims are supposed to be in there. It sound like the original laminate shims have been lost and someone cut their own shims from loose shim stock to replace them. There is nothing wrong with this, provided that it was done relatively clean and neatly. The important thing is that the bearing has the proper clearance. If in your judgement the hand cut shims were poorly done, you can get some shim stock and make your own. Laminate shim stock can be bought and cut to size. Buying shims from Leblond will be expensive (probably more that a sheet of laminate shim stock). Or you can just use loose shim stock. Either way, you should have a piece of .001" shim stock for fine tuning. What I would do is measure the shim packs from each bearing, replace poorly made shims and add some more shims (to the tight bearing) and start the bearing adjusting procedure over again. When the bearings caps are bolted down, the shims won't move.

I hope this helps!
Good Luck!
-Blue Chips-
Webb

Don't forget that the bearing expanders need to be correctly tightened. If they are too loose, the bearing will be tight enough to stop the spindle.
IF you price new bearings from South bend, be sure you are sitting down.

Dave

Thanks for the advice.

I assume the originals where cut to the approximate shape of the cap cross section? Is that important or are little pieces enough? Were they made of brass or steel?

What is "laminate shim stock"? I don't think I have heard of this. A stack of shim material stuck together?

I assume you need to tighten the cap bolts fairly tightly to compress and hold the shims.

OK, I see laminated shim stock sold by McMaster and others. It appears that .002 per lamination is what's available in steel or brass. Cut this to shape somehow and add one .001 for fine adjustment? Brass or steel or does it matter?

Hi There,

Originally they were brass. But considering costs, I would be tempted to use aluminum.

Dave is correct about proper adjustment of the bearing adjusters. If you have the SBL parts manual, the bearing adjustment procedure is in there. I think you can find it on-line if you look for it.

I mentioned having some .001" shim stock for fine tuning But you may not need it. As you mentioned, the laminates in the laminated shim stock are .002" thick. Peeling one laminate can change a bearing from being too loose to too tight. That is why you should have some .001" shim stock for fine tuning. Consider this cenario: Your bearing is too loose; you peel a laminate (.002") off; now your bearing is too tight (maybe); if too tight, cut out a .001" shim and put it in. That is a very simplified outline of the bearing adjustment. Like I said, use the bearing adjustment procedure published in the SBL parts manual. Also, when removing laminates, alternate the removal between the two sides of the bearing. You want to keep the two shim packs as close as possible to being equal in height (i.e. no more than .002" difference).

If you are going to make your own shims, try to cut them out in the shape of the bearing cap's contact area (slightly undersized is okay). They don't have to be perfect but you do want good contact area.

You mentioned that you had little bits of shim. This pobably is because someone tried to adjust the bearings. When they peeled the shim off, it tore into pieces (they are fragile and tear easily). Then they found out that they took too much shim off. So, they put the pieces back.

I hope this information is helpful.
Good Luck!
-Blue Chips-
Webb

The stock laminated shims are indeed cut to
the shape of the cap mating surface, and are
0.002 thick per peel. SB also installed a
0.001 individual shim in the bearings, so
that is added in or left out to trim the
clearances to within a thou.

Jim