On Wed, 2 Dec 2009 08:02:47 -0800 (PST), "
wrote:

On Dec 2, 2:31*pm, Ned Simmons wrote:


That may be true of resistors, but not bearings. For example, Barden
makes *only* precision bearings. Precision bearings also have
different cages than the bearing you get if you simply ask for a 6206.

I think it is true for most manufacturers. It has been sometime since
I read whatever I read.

I don't know for sure one way or the other. But besides the matter of
the cages I mentioned before, it seems marking would also be a
problem. Marking the part number would certainly have to be done
before final grinding of the assembled bearing, and more likely even
before heat treat of the components, which I assume is done after
rough turning but before the races are ground. That's pretty early in
the process to be selecting components.

I may have been reading about roller bearing
at the time with the emphasis on using the sizes that are relatively
cheap because they are manufactured for use on semi-trucks.


This is true. I was told by an SKF engineer that most of their ABEC 1
deep row bearings will meet ABEC 5 standards, and I've verified this
in a couple cases where I built very low speed spindles with sub-tenth
runout using ABEC 1 bearings. The fallback plan was to replace the
bearings with precision units, but it wasn't necessary.

So if most meet ABEC 5, what are the chances that some meet ABEC 7 or
9?

I wouldn't be surprised if the occasional bearing meets at least some
of the specs. My understanding is that the geometry and finish
requirements to meet electric motor bearing standards, which are for
the most part quietness specs, are the same things required to make a
true running bearing. On the other hand, EM quality does not require
especially tight tolerances on the overall dimensions of the bearing,
so standard bearings may be less likely to exceed their class in that
regard.

Like Ed, I've formed these impressions based on conversations I've had
with various tech support persons over the years, so take them with a
grain of salt.

--
Ned Simmons