Re: ATM - Incredible offer

[James P Crombie <jpcrombie@pei.eastlink.ca>]

The marks on the glass in photo two are left by surface grinding on a 
Blanchard grinder.  Commonly used to grind the two surfaces parallel.
For something this large it was problably done on something like this
http://www.blackclawson-cm.com/grinder.html
Big sucker :-)

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Date: Wed, 29 Oct 2003 12:02:31 +1100
From: Mark Suchting <masuch@cia.com.au>
Subject: Re: ATM Incredible Offer.

Joe

As far as I know, Corning only sells #7740 Pyrex in that size in 2 1/4"
thick sheets. They do not _mold_ telescope blanks. Post -processors like
Newport, United lens etc do the cutting, generating and annealing.

The ripply low spots remaining in the photo:

http://www.mwt.net/~nss/mirrors-2.jpg   look typical of the artifacts of
drawn sheet Pyrex to me.
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James P Crombie

Summerside		     Machinist
Prince Edward Island	     Amateur Astronomer
Canada			     3D Designer

E-mail			     jpcrombie@pei.eastlink.ca
Astronomy webpage 	     http://www.jamescrombie.com
Rhinoceros 3D webpage	     http://www.jamescrombie.com/rhino/
Mirror Grinder page          http://www.jamescrombie.com/pics/
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