From: "Dave McCarter" 
To: "Don Bates" ,
        "ATM" 
Reply-To: "Dave McCarter" 


> Should I pour a new lap prior to beginning the
> figuring phase?

Absolutely. The job of polishing and creating a sphere requires a hard thin
lap, else the edge will be turned and the surface will have zones and
roughness called dog biscuit.

Figuring requires that the pitch be slightly soft, as you are creating a
complex surface and the pitch must be able to more easily flow to match the
surface, even if you are using a sub diameter lap. It should be at least a
quarter inch thick.

If you need to cold press for an hour, then so be it. The new lap must be
well matched to the mirror.

The best shape to cut the channels leaves a star lap, and you figure from
the center to the edge.

Dave

--- BBBS/NT v4.00 MP