On Sat, 27 Oct 2007 12:54:12 -0700, Diamond Dave
wrote:

On Sat, 27 Oct 2007 14:40:54 -0500, Ignoramus2057
wrote:

Since I found a pair of 7209 Fafnir Abec 7 bearing amongs some of the
stuff I took home recently, I did a little research. Looks like ABEC 7
refers to a very precise grade of bearings that are usable at very
high RPM in machine tool spindles. (this one seems to be good for 22k
RPM, for example). This stuff is god awful expensive, like $300 per
such bearing at McMaster.

At the same time, if you search for ABEC 7 on eBay, you will see a
huge quantity of a buck a dozen "ABEC 7" skateboard or roller skate
bearings.

I have hard times believing that they are really made to such
specs. (or that skateboards need such precision)

Are those skateboard bearings really made to ABEC 7? Or is that some
clever marketing ploy?

Probably more of a lie than clever marketing. I use ABEC-7 bearings in my
Shimano Curado fishing reels and they really are slick. I get them he
http://mikesreelrepair.com/
And they aren't that cheap, but Mike sells them for less than anywhere else I've
found.
As far as I can tell, ABEC-7 bearing are supposed to have ceramic balls/rollers
and I have my doubts about how much shock they could take on a skate board
type use.

ceramic bearings are used in a locally made, internationally marketed,
model jet turbine.
I asked the guy how much shock load a ceramic bearing could take.
"Hmmm let me show you"
He had a beairng that they had cut apart using a dremel cutoff blade
and took a ball out of the bearing.
on the back peening pad on his 6" bench vise he placed the ball.
then he gave it one almighty whack with the largest size ball pein
engineers hammer. I mean he really laid into it!
on the bench vise could be seen a hemispherical dimple that looked to
be half the size of the ball. in the face of the hammer was a smaller
hemispherical divot.
the ball itself was lost down the back of the workshop because we
heard it smack the rear door.

some of those little balls can be damn near indestructable.

Stealth Pilot