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

["John Murray" <johnm@chello.com.au>]

Hi,
        A friend is almost ready to start grinding a 250mm mirror using a metal
tool. However the design of the tool needs to be finalised. What we have is
a 250mm diameter disc with a sagitta of 2.6mm cut into it(The curve
naturally is convex, Bad ascii art is below). 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? Any advice is appreciated.

Cheers

John Murray
Whyalla
South Australia

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