To: atm{at}shore.net
From: jsgrmfg{at}gracemfg.com
Reply-To: jsgrmfg{at}gracemfg.com


>The secret I found to making a good sphere without going through every
>defect in the books is keeping  the channels of the lap open to the same
>width.across the diameter of the lap. It does not take long before the
>channels will start to close in the center. This causes the surface area
of
>the lap that is in contact with the mirror to increase which cause more
>polishing action. For every 10 to 15 minutes of polishing, I stop and run
a
>hot soldering iron down the channels so they are at the same width. By
>doing this, I do not  have any major surface defects like turn down edge
>and it doesn't take a large effort to arrive at a perfect sphere.

    If only laps were so predictable.  And fixable. I have
seen beautifully made laps, precise to the point of prissiness and
thoroughly pressed, do awful and wholly unexpected things to a mirror.  I
have also seen ratty looking laps with half closed, irregular channels
behave perfectly and do fine work.  Pitch laps are terrible and mysterious
things.  At least the old ATM writers got that one right.  I think every
one of them warned about the unpredictability of pitch laps.

Jim Sturtevant

--- BBBS/NT v4.00 MP