Re: ATM A question on Metal tool design........

[Mimas@aol.com]

Jonh Murray wrote:

>We would like clarification on whether 3 concentric grooves and 3 radial 
grooves >would be sufficient. Also, should the radial grooves meet in the 
middle of the tool
>or should they terminate at the innermost concentric groove AND go all the 
way to >the edge of the tool?

John, I made a 10" metal tool from part of an old manhole cover.  I didn't 
make any grooves, either radial or concentric.  Initially, there were 
concentric ridges where the sagitta curve was stepped, (I calculated radius 
for every .001" change) but these were gone after I attained desired radius 
in the mirror blank with 80 grit.  I then made a dental stone tool with hex 
ceramic for subsequent grits.

If you intend to use the metal tool beyond rough grinding, I would be 
concerned with symmetric grooves as these might produce zones in the mirror.

Regards,