Re: [ATM] Polishing pads

["Bob May" <rmay@nethere.com>]

There are many on this thread that have had bad results with the
pads.  I attribute this mostly to the idea that they are
expecting a nice smooth sphere when they get done with the pads.
Nothing further from the truth is the fact.  The pads are to
polish up the surface so that the nice figure desired can be done
in short order to get that desirable figure on the glass surfaee.
I've tried with omse mirrors to do figruing with the pads and
have never gotten a decent figure (better than a half wave) and
even that was not a really nice figurre.
The pure object to using pads is to get the rough polishing out
of the way in short order.  As such, the pads can be used to
quickly get a smoothed surface without any pits in it for the
final job of figuring the surface.  I've seen zones, hyperbolas,
oblate spheroids and everything in between.  It is just a means
to get the job done without spending hours and hours slowly
pushing the glass back and forth.   Polishing pads are used like
you do hogging - fast and hard! Do a pad tool slow and it does
take a long time to do, just as if you did the work with a good
cutting lap.  (If you're going to be doing your stroking in
strokes per hour, you might as well do your work with pitch as
the time difference wont' be that much.
So, go and do your pad work hard and fast with a lot of pressure
and things will get done fast.  The pads don't move about like
pitch does with pressure so the surface won't develop something
strange that will take hours to get rid of like a deep hole in
the center.
I'll note that I prefer to use the most agressive thin pads
available as they will remove the most material in the shortest
period of time.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net


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