"RoyJ" wrote in message
m...
Current ball bearings are made to better tolerances than older ones. The
ABEC numbers (higher is better) have stayed the same but a 30 year old
ABEC-3 is pretty close to a current ABEC-1. And even the import specials
are pretty good.

Ball bearings are good for higher speed and lower friction. Sleeve
bearings are good for lower speeds, higher average loads, but have
slightly higher friction (means heat in the bearing). A sleeve bearing
actually floats on a film of oil (assuming it's properly lubed) so there
is no metal to metal contact. Ball bearing have metal to metal contact
because the balls squeeze the lube out of the point of contact.

Actually no; when the design is right there is still a very thin oil film
there (although it is vulnerable to dirt in the lube). Google EHL

Everything is hardened but there is still the wear factor.

Sleeve bearings take severe impact loadings better. The relevant surface
area of a 3/4" shaft is around 1/2" wide. Compare that to the 3 or 4 ball
point contacts in a ball bearing. Of course a roller bearing has much more
contact area, they are used for the high impact applications.

I have some bearing balls out of a race car CV joint that show nasty
cratering under a 10x magnification. You can see rows of chips taken out
of the hardened surface, look almost like the gouge marks from a backhoe
tooth on a concrete road surface.

No again, the cratering will be pits produced by fatigue cracking, caused by
stress cycles. But as you say, the stress levels are very high

Ignoramus20387 wrote:
On 2009-03-13, RoyJ wrote:
1) properly lubed sleeve bearing have a longer service life in certain
applications like furnace blowers. In the 'old' days, they were used in
the majority of motors since ball bearings had both shorter life and
were much more expensive.
What about modern balll bearings?
i