To: ATm{at}shore.net
From: "Matthew L. Brown" 
Reply-To: "Matthew L. Brown" 


Bill,
  Don't fret too much about the chips, but DO keep the edges beveled.  My
1st mirror had an equivalent chip in it, with a sharp edge. I kept it
bevelled with an oilstone, and it caused no harm during the entire grinding
and polishing process.   It was actually useful during
final figuring stages where I used it to insure I made an integer number of
mirror revolutions.

It's too deep to grind out.  But it won't detract much from the reflective
area of the mirror, and will mostly be hidden in the 1/8"wide bevel
you will grind into the edge of the blank.

Do check for strain (a nice photo of the polarizer test is here:
http://www.megspace.com/science/sfe/i_fa_art.html#strn )

KEEP ALL EDGES BEVELLED.
Link for how to bevel it:
http://www.stellafane.com/atm/atm_grind/atm_bevel.htm Bevel early.  Bevel
often.

=Matt


>>Hello,
>>I have a 16.5 inch port hole, and is 1 inch thick. On one side, it says
>>Heat Treated", do I take this to mean that it is stressed
glass?. To get a
>>quick response from everyone  " Can this be used as a mirror
blank"? If so,
>>each side has a minor chip along the outer edge, the smaller of the two, is
>>1.5 inches long, 1/16 deep and 3/16 wide (across the glass surface). The
>>other is not much worse, just longer and slightly deeper. Can this be ground
>>out?; the surface seems to be fairly flat using a metal carpenters measure.
>>I would like to make a RFT, if I can use this thin glass.
>>
>>Thank you,
>>
>>Bill Morgan
>>(alias.. Arthur)

--- BBBS/NT v4.01 Flag-4