"Karl Townsend" remove .NOT to reply wrote
in message ink.net...
Pay attention to the caution already offered on grinding steel. Diamond
is
destroyed by steel when applied at high speed----it actually is
dissolved
into the steel, cutting its useful life very short by dulling it until
it
doesn't cut well. Relieving it on an aluminum oxide wheel at a
greater
angle is the typical method of avoiding contact with a diamond wheel.
Using
a green wheel presents the same problems that diamond does---it, too, is
soluble in steel. It's silicon carbide.

Harold,

I've gotten fair life out of the green wheel for ruffing brazed carbide
bits
on the the Baldor grinder. But I'm sure I'll have to replace it sometime.
I've not seen aluminum oxide Baldor wheels, are they made?

I trust you're talking about the steel backed wheels, on which you use the
face to grind, not the periphery. Yes, they're available, but are not
cheap. If you intend to stay with the green wheels for carbide (I don't
recommend it, and if you once try diamond you won't either) it's easy enough
to go to an aluminum oxide wheel on a different spindle to grind the steel
back to avoid contact. You'd do that with a diamond wheel, exactly the same
way. That's what I've always done with diamond wheels, or when I had no
choice but to use the green wheels.


Will aluminum
oxide cut carbide at all? I always thought carbide just bounces off.

You've pretty much got it. Aluminum oxide is a lot softer than silicon
carbide, but grinds steel far better because it *doesn't* dissolve into the
steel the way silicon carbide does. Carbide is slowly ground by aluminum
oxide, but at the expense of dulling the grain prematurely, much the same
way steel does silicon carbide, but for different reasons.

I've always used the green wheel cause I don't know any better.

In the scheme of things, it doesn't make a big difference, Karl. If you
are the typical home shop type that occasionally sharpens some brazed
carbide, the worst case scenario is you'll buy one extra wheel in your life
time because you waste a little when you grind steel. Because green wheels
are bonded softly, they are quite friable and break down quickly, which is
the chief reason they work as well as they do when grinding carbide. Keep
in mind that the silicon carbide is *not* any softer, just the bond. If
they didn't break down, the dulling would quickly bring the grinding to a
halt. When you grind on steel, although it's quite soft, the grains
dull very quickly and are shed, exposing new, sharp grains. That's where
you experience the loss. As I said, for casual use, no big deal. The
only real issue would be a health one, which is silicosis. Breathing the
dust is not a good idea, and you make plenty of it when you shed the wheel.

Harold