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[ATM] Finished fine grinding
While waiting for my basement to warm up, (It was 55 degrees F tonight) I
have resumed a very old project. I was working on a pre-generated 12.5 inch
f/7 or so mirror I bought some years ago, ground to my long forgotten spec.
When I began the project, I started years ago with 220 SiO as I recall. I
resumed a few weeks ago and gave it an hour with 220, followed by 320, and
500 SiO. I then began with the white powder. 15 Micron, then 9, 5 and
tonight I finished with 3 micron. Each grade from 220 on down lasted an
hour, The wets after 330 each lasted ten minutes each of true glass over
glass time. (Occasionally I had to add some water during the wet to keep
things moving along.) I spent the first three wets of each grade with the
mirror on top followed by a good scrubbing and then three wets of tool on
top. Everything was cleaned to within an inch of it's life between grades
of abrasives.
I applied no pressure while grinding other than the weight of the glass
itself. I know that there are diverse views on the subject, but this method
seems to work fine for me.
The motion of the glass over glass was as smooth as... well... glass. I
suspect that I have a very good spherical form right now.
My next project will be the pitch lap, followed by waiting for the weather
to turn, not likely too soon as we are expecting a righteous snow storm in
the northern suburbs of NYC over the next two days.
Once that is done, I will begin to make the patterns for my various casting
projects including a mirror mount, pedestal feet, altazimuth mount, and
finder scope holder, and probably more. That should lend itself to working
upstairs, which will definitely make my wife happy as she will get to see
me again in the evening.
Warmest regards to all,
Francis J. O'Reilly
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