ATM Newport's plate glass tools.

[Richard Schwartz <richas@idt.net>]

David, John Dobson has written that "faults of the tool are not
contagious onto the mirror".

However, it is my humble opinion that you should set the glass tool
aside and make one from tiles and dental stone.   This will be really
easy for you because the approximate curve is already pressed into your
mirror blank.  At this time, you can also make a dental stone foundation
for your pitch lap.   If you are really lucky, you will never discover
the advantage of a separate pitch lap foundation.

The main advantage of the tile tool is superior fine grinding,
especially at the edge of the mirror.   This advantage comes about
because the channels between the tiles allow a better distribution of
the grit over the grinding surfaces.

Plate glass tools are generally not thick enough to make decent mirrors,
but if you want to try it, I can BEND the curve into it for you.   That
way you minimize the removal of glass from a piece that is already too
thin, and you save a lot of the work of hogging out a curve.  You also
get some assurance that the plate glass is properly annealed.

Anyhow, it is something to think about.

. . . Richard

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Date: Thu, 31 Dec 1998 03:47:58 -0800
From: "David Reynolds" <davidrey@ij.net>
Subject: ATM Newport's plate glass tools.

Hi, my name is David.
I am starting my first mirror and received a kit (KITED800B) from
Newport
yesterday.
Both tool and mirror have f/8 machine generated curves. The tool in the
kit
has concentric rings radiating out from the center. I noticed that there
is
a low zone on the SURFACE of one of the rings that didn't get ground
when
the curve was generated. The low area follows the ring about 3/4 the way

around and occupies the entire width of that ring (about 3/8 inch wide
and
1
1/2 inch from center.) It just appears as an area that has not been
abraded
with a few places inside that have been. It doesn't seem very deep (less

than the thickness of a page from the newspaper). How will this affect
grinding the mirror? What precautions should I take?
Also, has anyone here used this type (ringed) tool before? What is the
proper way to use this type of tool?