Re: [ATM] make pitch lap tool

[Dave Gee <dave4gee@yahoo.com.au>]

G'day Horace,

I cast a dental plaster lap about 25mm thick for a
10inch mirror.  For a 16, I'd go for about 30 to 35mm.

FWIW, once I start polishing, the tool never leaves
the glass for as long as I can manage it. 10hours or
more.

After casting and a day or two drying, I drill a 10mm
hole through at about the 70% zone.  after a further
week I varnish it and pour the lap and fashion the
facets, putting the hole at the intersection of a pair
of grooves.  CeO is then injected through the hole
every 1/2 hour or so with a syringe.  Every 3 or 4
hours I stop the machine and inspect the condition of
the lap through the glass and if the facets arn't
merging I continue on, not separating the tool and
mirror. 

Here is a movie of my machine "Donkey" polishing...
http://www.youtube.com/watch?v=HVyyrI49LpQ

and for good measure, here is a movie of Donkey rough
grinding the back...
http://www.youtube.com/watch?v=DFQ3EkMYnQo

The method you mention (90% and tip down) is the way I
separate them, after I can't stand the wait any
longer. :-)

Regards
DaveGault
AUSTRALIA

> I am getting ready to make a 16 in pitch lap tool...
> backing and weight ?...pulling the tool 90% I tip it
> down to break suction...is there a better method ?


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