Re: ATM chasing spheres $%$^&*(%^&$%^!!!!!

[Cary Chleborad <bennu@ns.net>]

Richard Schwartz wrote:
> 
> You did not say the size of your aluminum tool; I presume it is 8" just like your 
>mirror.
>

Whoops! Forgot to specify, I'm using a full sized tool.

 
> I suggest that you grind with a pipe flange, or even a flat stone, 4" >in diameter.  
>Try to concentrate the grinding on the center of the >mirror. You will hog out a nice 
>curve.  After you get the saggita >right, go back to aluminum for a superior fine g
>rind.

I've been fully hogged out since i started 120 grit.  My sagatta is
right on, well within .001" and I'm nearly spherical, I just can't seem
to get full contact between the tool and mirror.  Am I being too picky
at this grit for a machine?  I know I can get what I want by hand, but
that's not the point.

I'm using graphite to test the contact between the tool and mirror and
there is a raised ring from the 37% to 75% of the radius.