From: "mlbrown{at}everstrive.com" 
To: atm{at}shore.net
Reply-To: "mlbrown{at}everstrive.com" 


Here's a foucaultgram of a 6" f8 with a big chip taken out of the side
(look at the 12 o'clock position, next to the safety clip). This chip was
due to the blank being dropped onto the tool in the bucket during rough
grinding.

http://host67.everstrive.com/~mlbrown/ASTRONOMY/FoucaultTest6s.jpg

Works fine.  Keep the edge bevelled, contouring around the chip.  It'll be
easy to spall off little chips as you bevel, so clean the mirror carefully
after bevelling (note short 1/4" scratch at 8:30 position, about 2/3
radius).

Also, take some care when pressing the lap to insure that there isn't any
lap material where the chip is -- otherwise that part of the lap will
protrude high and polish a ring there.  Talk about turned-down-edge!

=Matt






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