In article , Jeff Rininger
says...

When you have the headstock set up for boring, would it make sense to
bore for some sort of tapered roller bearing to replace the stock
sleeve bearing?

No, not on a 9" south bend. The ones where the steel spindle
runs right in the cast iron headstock casting don't really have
enough meat around the bearing to put in a tapered roller bearing.

Because the bearing has to be shim-adjustable by clamping down
on the clamp bolt, that region has to be thin enough to flex
and close down when the shim is removed and the bolt tightened.

It's not clear that tapered roller bearings are really better
in this application, either. Those journal bearings in those
machines may well be one of the most widely disseminated kind
of spindle ever made - south bend must have made a bazillion
of those 9" machines, and most of them are still out there
kicking around, working.

Jim

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