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Mark Harry
Carpal Tunnel
Reged: 09/05/05
Posts: 2490
Loc: Northeast
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Where can you get Pyrex sheet, of about 1/2" thickness? Or has the supply factor made it unavailable?
Mark
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Scopes in the works-
Too many for putting down here! Favorites- 8" F/6, 8" F/4.72, 4.5" F/5.4, 14" F/4.455, all completed.
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Mike I. Jones
Pooh-Bah
Reged: 07/02/06
Posts: 1102
Loc: Fort Worth TX
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Did you try Newport Glass or Glass Fab?
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and a new design you'll like.
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Glig
sage
Reged: 10/02/05
Posts: 270
Loc: Baltimore, MD
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United Lens sells 12 X 12 inch square sheets 0.5 inch thick for $45. Its precision annealed pyrex in rolled sheets.
Pyrex glass at 0.5 inch should be water jet cut. You can get almost the full diameter that way.
Plate glass at 0.5 inch, should be circle cut.
Circle cutting by hand costs nothing but is wastefull of glass by comparison: the most you can get out of a 12 inch square is 8 inches diameter. There needs to be 2 inches minimum distance to the edge all the way around, otherwise the cut will leave an gouged and rough circle. But for 1/2 inch plate, circle cutting makes much more sense.
With the circle cut done you use a blunt chisel, hammer and pliers  to break away the excess. You don't want to try your hand at circle cutting if you've never seen it done.  tricky stuff. 
I've gotten a lot of blanks circle cut myself. BTW done right, the circle cut side is as round as water jetting can do. The other side, well is not so good. But I've seen water jet do just as poorly on its bad side!
You may want to consider the cheap and dirty option of using plate glass: You can forgo the added expense of grinding both sides flat, water jet cutting, and the higher price of pyrex.
United Lens are also the best place to buy standard thickness molded blanks. I've bought a lot of blanks from them. Maybe 50 in all. They can send you a PDF price list by e-mail.
United Lens Phone# 508-765-5421
Richard
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Richard Caldwell
Edited by Glig (11/27/07 09:39 PM)
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Mark Harry
Carpal Tunnel
Reged: 09/05/05
Posts: 2490
Loc: Northeast
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I did inquire at Newport, but got no reply. I'd be cutting secondaries from it, nothing large as primaries. M.
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Scopes in the works-
Too many for putting down here! Favorites- 8" F/6, 8" F/4.72, 4.5" F/5.4, 14" F/4.455, all completed.
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Glig
sage
Reged: 10/02/05
Posts: 270
Loc: Baltimore, MD
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If I were making secondaries I would go one step farther and use fused silica. I would contact Reco labs or Superior Optical supply. United lens should do just fine for Pyrex though.
I always thought making secondaries were a big undertaking unless you have a nice setup for it like a planetary polisher. Do you have something like that?
Richard
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Richard Caldwell
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Mark Harry
Carpal Tunnel
Reged: 09/05/05
Posts: 2490
Loc: Northeast
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No, I'm referring to Cass secondaries, mostly finite ROCs. I can make flats easy enough, but not in the sizes I want/ quantities I'm interested in, at least for now.
I could block up 50 or so 1" elliptical pieces, but what do I do with such a quantity? Not exactly the direction I care to go at the moment.
I have capacity to cut 1-3" round blanks. If I had the specified thickness pyrex available....(fill in the blank time) Mark
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Scopes in the works-
Too many for putting down here! Favorites- 8" F/6, 8" F/4.72, 4.5" F/5.4, 14" F/4.455, all completed.
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Glig
sage
Reged: 10/02/05
Posts: 270
Loc: Baltimore, MD
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Quote:
If I had the specified thickness pyrex available....(fill in the blank time) Mark
Well you DO have that available.  United Lens sells it as I've mentioned.
"United Lens sells 12 X 12 inch square sheets 0.5 inch thick for $45. Its precision annealed pyrex in rolled sheets."
Richard
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Richard Caldwell
Edited by Glig (11/29/07 12:39 AM)
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