Re: [ATM] recycling grit

["Bob May" <bobmay@nethere.com>]

Hogging out the sag. is what I mean.
The process is pretty easy.  Grab a 4" wheel and attach it to a
speaker magnet that is a out 3" of so in diameter for a handle
(no screws through to bother the other side).  Harbor Freight
sells these at 3 different disks for $10 on sale frequently.
Splash some water on the mirror blank and start stroking the
glass with firm pressure and you will see it erode quite quickly.
Using significant pressure and good speed and you can carve out a
12" mirror in a few hours to a F5 shape.  Remember to stay away
from the edges until the final grinding part otherwise yoiu will
just be removing glass without getting any deeper with the sag.
Straight strokes or doing circles with the diamond both work well
and you will probably want to mix them to gain  more glass
removal.  The only thing that you end up with is glass dust
which, of course, needs to stay wet.  Cleaning of the surface
should be done before the water and glass turn to a cream as at
that point you will be regrinding the ground off glass more than
actually grinding more glass off of the blank.
It's been a year since I've used one of the irno tools to do the
coarse grinding to make the hole in a blank and the reduction in
the need for 80 grit has gone down a lot.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

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