[ATM] Pitch laps!!!

[Richard Ozer]

Norm,

For a new tool:

Cover the mirror with aluminum foil or thick plastic wrap. Then, build a
cardboard dam around the mirror (or use a springform pan if you can find one
that large.  It's then safe to pour the plaster and match the curve.  It's
better not to use a flat disk.

Regarding using the tile tool.  We do that all the time in our workshop...
however, if you find that you need to go back to fine grinding, having the
tool covered with pitch is not particularly helpful :-p


-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Norm Prince
Sent: Sunday, April 08, 2007 1:59 PM
To: atm at atmlist.net
Subject: [ATM] Pitch laps!!!

Okay I spent an hour and change searching the archives on the subject of 
pitch laps and learned a bunch of stuff and found some great ideas to help 
me make one for this 12" project.  Alas i didn't find the answer to the 
question that's been sloshing around in my head.  I'm about to move on to 
5AO so as usual i'm trying to think ahead.

Here is what i've been thinking:  I'd rather not make the lap out of the 
tile tool I've been using to grind on the chance that I might have to go 
back to grinding if I've made any horrible mistakes that will take forever 
to polish out.  So I was going to pour another plaster disk to use as a base

for the pitch lap, but i'm really freaked out about scratching things and 
don't want to get plaster anywhere near the mirror.

The question(s) is then will a flat plaster disk be acceptable...or should 
it have the same curve as the mirror to become a pitch lap?  Should I just 
go ahead and pour the lap on the tile tool i've been using?

I also came across an opinion in the archives that plaster would be bad to 
use for a pitch lap...anybody have any info on that?...is a sealed plaster 
disk okay?

any nudges in the right direction would be greatly appreciated as always.

-norm prince-
Georgia, USA 


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