Re: [ATM] Tom's back - Parabolizing Plate Glass 12.5" x 0.73" f/5.5

["Mel Bartels" <mbartels@bbastrodesigns.com>]

> What do you mean by "heavy towards the center and lighter towards the
> edge."
> I'm having a hard time picturing what you are describing.


Imagine the inner portion of a parabolic curve that's plotted on graph
paper.  It has a very gentle spherical curve with slightly increasing
curvature near the ends.  That's the shape of the pitch channels.

Start with 1 inch pitch squares with 1/8 inch channels.  Very gradually
increase the width of the channels so that at the 70% zone the width is 2/8
inch thick and at the 100% zone the width is 3/8 inch thick.  This is a
partial parabolizing lap which I've found best.  Actually the best is an
oversized partial parabolizing lap, but since oversized laps are relatively
unknown in the amateur world I won't mention them much here.

Mel Bartels


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