Re: ATM Hogging Out

[Guy Brandenburg <gfbranden@earthlink.net>]

Have you tried simply moving the mirror (MOT) around in a very wide
circle over the tool? Digs out a lot of glass in a hurry, we find. Of
course, you get an absolutely horrible figure; but that can easily be
smoothed out later with a traditional 1/3 COC stroke.
Guy Brandenburg

Bill Kelley wrote:
> 
>   To all:
> 
>   It occurred to a young friend and I, as we were hogging out an 8 inch
> mirror tonight, and starting with two 8 inch blanks, that perhaps the
> chordal stroke that everyone seems to use for hogging out is not the fastest
> way to dig a hole in the center of the mirror.  So we put the mirror on the
> bottom, sprinkled 80 grit, and spread it around with the tool.  Then our
> hogging stroke consisted of pressure on the edge of the tool sweeping back
> and forth over the center of the mirror with about a 4 inch stroke and heavy
> pressure on the edge of the tool.  As the edge of the tool was being driven
> into the center of the mirror, we continued the usual rotation of the tool
> and walk around the barrel.  This dug a hole very quickly; much faster than
> the traditional chordal stroke mirror on top.  To bring the rough figure
> back to a sphere; every third charge of grit, tool still on top and heavy
> edge pressure, we started our strokes with the tool concentric on the
> mirror, and the edge of the tool stroked just across the center of the
> mirror.
> 
>     We didn't do a sharpie test, but with the mirror back on top and with
> very wet worn out grinding slurry, the bubbles that formed distributed
> uniformly, moved off the tool and left us with two congruent surfaces that
> did not seem to stick.
> 
>     I may well be that there is nothing new about this, but when you don't
> know about something and you try it and it works very well, it is very
> rewarding.     : ^ )
> 
> Bill Kelley