Re: [ATM] Pitch Substitute for very fast mirrors

[Kevin MIchael Zabbo <chaosopher23@yahoo.com>]

Even that subdiameter lap has .0002" space between the
high and low part of the contact area.  Heavy weight
during figuring gives a rough surface.

Also, silicone is a bit cheaper than pitch and doesn't
form that stench that my wife hates.  She can deal
with a little vinegar (foodlike) rather than
turpentine burning.  Better a happy wife than a nice
pitch lap?

Kevin of Forest, Mississippi
Found the darkness

--- hermit <hermit@outofoptions.org> wrote:

> Kevin MIchael Zabbo wrote:
> > Pitch does have a lot of useful characteristics
> that I
> > won't get into here, but it has a flaw that I need
> to
> > point out.
> >
> > Fast and large mirrors, say 13" f/3, have a
> deviation
> > from sphere that can be measured on a decent
> > micrometer, which is far too big a gap for pitch
> to
> > conform.  The pitch, even if soft, takes a long
> time
> > to flow.
> >
> >   
> Have you tried heavy weight with pitch?  It works
> better if you have a 
> machine, but slow speeds and heavy weights work
> well.  Plus, you are 
> using a sub diameter lap so there should be less of
> an issue in terms of 
> flow.
> 
> Ken Lowther
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


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