Shattering Stone

Shattering Stone

Last week when I was explaining the steps on how I created my shift knob, and it was pointed out to me by a fellow Ferrari fan and aircraft mechanic that using a grinding wheel to remove soft metals is dangerous. The soft metal embeds itself in the grinding stone causing an imbalance which can cause the stone to shatter! Here’s what he suggests using instead:

We use a lot of different sanding tools with aluminum.  For those indents, there are some drill-mounted tools that could help.  One type is a sanding disc mounted on a rubber disk mandrel.  What we use now is the Roloc system made by 3M.  We use one inch and three inch diameter holders and disks.  There are a wide variety of grits of abrasives available.  In sandpaper, I have seen from 36 grit up to 180 (280?).  There are also disks of different grades of Scotch-Brite material, and also disks that are more of a polishing type.

We also use drill-mounted sanding drums.  Expanding cylindrical rubber drums of 1/2 inch, one inch, and two inch diameter.  The drums are from about 3/4 inch to one inch long.  And with these also there is a variety of grits of sandpaper available.  I don’t know the vendor for these.

Drills are not the only way we run these tools.  We also use small pneumatic high-speed grinders….10,000 rpm or so.  You can remove a lot of metal!!

Another type of portable-powered tool would be a rotary file.  There are dozens, if not hundreds, of shapes.  Put it in your drill or high-speed, and start making chips!!

I don’t know where to tell you to go to get this stuff.  I just go to the tool crib at work.  What I can do is check the names of some industrial supply catalogs and send those to you.  Two national companies I remember off-hand are Grainger and McMaster-Carr ( and, but I don’t know without searching what they have along the lines I’ve mentioned.

Back to the bench grinder.  Generally speaking, nothing should be worked on a grinding wheel that leaves bits of itself behind stuck to the wheel.  Brass, bronze, aluminum, copper, etc. are all too soft.  The material being worked has to be hard enough to take material off the grinding wheel at the same time the wheel is grinding away material.  Did that make sense?  Bottom line, a stone that comes apart at 1700 rpm will do nasty things to nearby Ferraris……and people, too!

There.  I’m done preaching.  Thanks again for sharing your experiences with your car(s).  It’s a lot more affordable for me to read about it than do it!!

Jerry Mahler

Thanks Jerry for showing me the right way, and the safe way, to do things!

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