Re: ATM 21" f/6 - Status report and a question

[Hugues_Laroche@ses-astra.com]

Hi Ken,

>Question:
>=========
>I'm planning on using gugloz #64 pitch

Can't comment on this (never used Gugolz)

>on a full size pitch lap, MOT to do the polishing.

When contact will be good, a 21" lap will be _very_ difficult
to move. You will probably not be able to do more than
10-30 min polishing at a time before to be exhausted and if you
do too much at a time, your back will ache for a few days.
Did it very recently (20" lap), TOT on a 26". When you work MOT
just make sure the mirror does not slip and fly across the room:
experience has shown that mirrors do not fly well and rarely
come back like a boomerang ;-)

>  I think I'll use the method described by Texereau to make
>the lap - pouring the pitch into molds and cutting tile squares.  What
size
>pitch square do you all think is good for a 21" polishing lap?  The book
>shows 3/4" squares, but will larger ones work?

My 20" lap has 1" squares made a la Texereau. Very neat, I never
made a nicer lap by another method. But what a p... in the b...,
I was nearly driven mad by doing it... would never do this again:
I tend to prefer quicker methods now.

Keep working on it, a good 21" mirror is something to have!
Happy ATMing,

Hugues