I was working a thin (3mm) piece of aluminum plate with a rotating disc
on a hand drill. On the disc was a cutout of scotchbrite. *All of a
sudden* the aluminum went from having beautifully fine arcing scratch
marks to this hard marble orange peely crap. I assume that *something I
did was wrong* and that the work is now "work-hardened"?

If so, or not, how would I prevent such a thing? Is it a matter of use,
speed, heat, or what? And how can I remove it from the piece I have.

As always TIA.

Shon Shampain wrote:

I assume that *something I did was wrong* and that the work is now
"work-hardened"?

The pad got to hot and melted?


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de

Any chance the pad loaded up with galled aluminum, so that you were
basically trying to polish aluminum *with* aluminum?

Abrade or machine it flat and start over...

wrote:
Any chance the pad loaded up with galled aluminum, so that you were
basically trying to polish aluminum *with* aluminum?

Abrade or machine it flat and start over...


I think that is exactly what is happening, as I have seen this exact
behavior with normal abrasive discs as well. And I know they clog up
readily, as the splotch of aluminum is hard to miss. I suspect that if
I include a cleaning step every pass, the problem may disappear.

On Tue, 27 Sep 2005 13:51:10 +0200, Shon Shampain
wrote:

I was working a thin (3mm) piece of aluminum plate with a rotating disc
on a hand drill. On the disc was a cutout of scotchbrite. *All of a
sudden* the aluminum went from having beautifully fine arcing scratch
marks to this hard marble orange peely crap. I assume that *something I
did was wrong* and that the work is now "work-hardened"?

If so, or not, how would I prevent such a thing? Is it a matter of use,
speed, heat, or what? And how can I remove it from the piece I have.

As always TIA.
You are trying to abrade aluminum oxide. It's hard. Clean the
scotcbrite or use new. Use some kind of cutting lubricant. Kerosene,
WD-40, light cutting oil, wax etc.
ERS

Another thought - try using the silicon carbide grades of Scotchbrite.
They cost a bit more but you will be hitting the surface with a grit
that's harder than the aluminum oxide coat already there.

Eric R Snow wrote:
On Tue, 27 Sep 2005 13:51:10 +0200, Shon Shampain
wrote:


I was working a thin (3mm) piece of aluminum plate with a rotating disc
on a hand drill. On the disc was a cutout of scotchbrite. *All of a
sudden* the aluminum went from having beautifully fine arcing scratch
marks to this hard marble orange peely crap. I assume that *something I
did was wrong* and that the work is now "work-hardened"?

If so, or not, how would I prevent such a thing? Is it a matter of use,
speed, heat, or what? And how can I remove it from the piece I have.

As always TIA.

You are trying to abrade aluminum oxide. It's hard. Clean the
scotcbrite or use new. Use some kind of cutting lubricant. Kerosene,
WD-40, light cutting oil, wax etc.
ERS

Using SiC really doesn't help at all because just as soon as the aluminum
starts sticking to it, you end up with the same problem. The only thing to
do is to use a lubricant to keep the aluminum from attaching itself to the
abrasive and thus cause the problem.

--
Why do penguins walk so far to get to their nesting grounds?

A little dish soap + water avoids that problem when blending aluminum
panels. We've found in our process that SC pads last longer and yield a
better finish than AO pads.

Bob May wrote:
Using SiC really doesn't help at all because just as soon as the aluminum
starts sticking to it, you end up with the same problem. The only thing to
do is to use a lubricant to keep the aluminum from attaching itself to the
abrasive and thus cause the problem.

--
Why do penguins walk so far to get to their nesting grounds?

"Tim Killian" wrote in message
...
A little dish soap + water avoids that problem when blending aluminum
panels. We've found in our process that SC pads last longer and yield a
better finish than AO pads.


It's commonly accepted that silicon carbide is the abrasive of choice for
sanding or grinding aluminum.

Harold