From: Dave Baker
Subject: Re: Grinding aluminum?
Date: 18 Feb 1999
Newsgroups: rec.crafts.metalworking

>From: Dale Borgeson <dalebor@yuck.net>
>
>In the intro machine shop course I took the instructor took great pains to
>make sure that we NEVER used aluminum on the the pedistal grinder. He said
>that it would clog it. Every once in a while a wayward student would grind
>some Al and it certainly did clog the grinding wheel and the instructor
>would go balistic.
>
>So my question is: Is there a gringing wheel which is appropriate for Al?
>I can't find any reference to this in any of my books or in the MSC
>catalog.
>
>On a similar line, what is the appropriate grinding wheel material for
>Carbide?

It isn't common to need to grind aluminium because there are no situations
where it can be heat treated to a hardness that prevents conventional
machining. There are applications requiring great accuracy though and one of
these is on Formula 1 type engines which do not use gaskets between the head
and block. In fact gaskets are only necessary to overcome machining
inaccuracies in conventional assemblies and many machines would operate better
without them if surfaces were true enough.

On F1 engines the blocks and heads are surface ground to a tolerance of 1/4 of
a thou over the length and width of the engine and special surface grinding
equipment has been developed to do this. Grinding of aluminium is therefore
perfectly possible with the correct grade wheels and lubrication. For ferrous
materials, aluminium oxide wheels are most commonly used whereas silicon
carbide grits will grind non ferrous materials. The harder the material to be
ground the softer the grinding wheel which may appear odd in terms of
conventional machining.

Carbide is the hardest material in common use and the wheel to grind it is
therefore the softest - i.e. green grit wheels as has already been said. Normal
wheels will generate excessive heat when grinding carbide and they remove very
little material. Green grit wheels generate adequate stock removal but wear out
extremely fast themselves. This is necessary so that the wheel continually
exposes fresh cutting surfaces to the carbide. For accurate finishing of
carbide tool bits it is more usual to use a diamond impregnated lapping wheel
which is used well lubricated with oil. Very fine grit conventional wheels will
also put a good finish on brazed carbide tip tools but with high stock removal
from the wheel itself.


Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. .