ATM Polishing with pads lesson learned.

[Dale Eason <atmpob@yahoo.com>]

I found my problem.  The tool had I high center.  
Thanks Richard S., Bob May and others.

Now for how that happened.  I cast a tool from my fine
ground blank.  I used two pieces of Saran wrap.  I was
not carefull and the Saran wrap had several wrinkles
across the middle of the tool.  At the time I was not
concerned because I was going to use pitch on top of
it.  Then I decided to use the pads.  I thought the
wrinkles only went down into the tool but didn't think
much of it one way or the other.  I should have fine
ground the tool to the mirror.

How I diagnosed the problem:
The outside was not polishing.  Many things can cause
that.  The tool would rotate very easily. Never used
pads before so didn't know if that was bad.  Foucault
showed steep hole getting steeper each 30 minute
session.  Not getting any better so maybe time to
diagnose.

After the tool dried out I could see that pads in the
center had a different appearance than the edge pads. 
I think only center were touching.   I decided to try
using the Sharpie test.  After about 5 strokes the
center lines on the mirror were gone but the last 2
inches of edge stayed and stayed.  Thats when I new
for sure that the edge was not being touched.

Richard said remove some pads and that got me thinking
why should they be high.  Then I realized that the
wrinkles in the hydrostone also went above the surface
and so some pads were raised.  All of the pads on the
wrinkles had a different appearance.

I fixed the problem by putting pads on the tile tool
used for fine grinding.  It is hard to rotate and push
(ok so now I know).  After 1 hr of polishing much of
the remaining sharpie has disappeared and the foucault
image is showing it heading back to a sphere.  More of
the outside is polished.

Thanks all.

Dale Eason

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