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Old 06-01-2019, 08:11 PM
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billdan (Bill)
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Join Date: Mar 2012
Location: Narangba, SE QLD
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For use as a primary mirror the glass would have to be reasonably thick.

The Diameter / Thickness ratio should not exceed 10:1 to be safe, e.g. a 250mm diam glass should be no thinner than 25mm. However I have read some amateurs going to a 20:1 ratio with no problems.

Also you can't use tempered or toughened glass as it will shatter during the grinding process.
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