From: "Frank Ward" 
To: "Bob Mazzullo" 
Cc: 
Reply-To: "Frank Ward" 


Bob,

>If I am completely wrong in my assumptions here, would someone please
explain to me where the differences lie?<


Howard, among others suggested microfaceting back in the early 60s. I've
done it since then. The large squares allow the pitch to move around with
the changing shape of the glass. That's their purpose. Microfaceting is in
addition to the squares. In the last stages of polishing I use a mat from
Wal-Mart's craft department used for needlepoint. The squares are around
1/8" inch. I blowtorch the lap surface, lay down the mat, press with a
CEO'd mirror with 40lbs for ten minutes. The resulting points are what you
want. When I remove the mat it is in the sink under warm water. I have
found that removing it just by pulling will remove a lot of the points too.

Now you have squares with thousands of little points on top. Get the lap
warm again and repress the mirror to take off the points on the micro
facets. When you sprinkle CEO and add water the resulting squeaking is
music to your ears.

As you finish polishing and start the beginning of figuring add one more
touch. The points will have worn down by now so add the finest screening
you can find. I use a disposable hair net. Just lay it on top of the lap
and cold press over night. The hair net is so fine it hardly sticks to the
lap. Now you are ready to figure.

It takes a lot of work to get a fine surface. If you are willing to settle
for a 1/8th wave mirror don't bother, but if you want 1/teens wave mirrors
you have to go the extra mile. At least that's my opinion.

The microfaceting gives a surface that readily adjusts to the changes in
the mirror surface. That way you can use a harder pitch for a better
surface but still retain the "adjustable" qualities of the pitch.

Frank Ward
Still Raining.
-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of Bob
Mazzullo
Sent: Wednesday, August 20, 2003 11:22 AM To: atm-digest{at}shore.net
Subject: ATM re: microfacetting pitch lap during final mirror steps



Hello everyone....

A techniques which I see sometimes mentioned is microfacetting of the pitch
lap with window screen, plastic netting, etc. Are there distinct advantages
to microfacetting the pitch lap during polishing and /or figuring that
would indicate that it should be done as a necessary step? Also, if
microfacetting is beneficial, why are the pitch squares themselves cut
fairly large, instead of smaller, when you are making the pitch lap to
begin with? I may be shooting from the lip here, but wouldn't it be more
efficient to cut smaller pitch squares, and use microfacetting as well?

If I am completely wrong in my assumptions here, would someone please
explain to me where the differences lie?

Thanks,

Bob Mazzullo

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