From: "John McLean" 
To: "Jerry B. Hillman" 
Cc: atm{at}shore.net
Reply-To: "John McLean" 


Hi Jerry,
 I have been working a 16" f4.5 mirror for a while now. I used Durhams
"Rock Hard" water putty for my tool. This stuff is sold in 5#
cans and it take 3 cans to make a good 2" thick tool. It looks just
like dental plaster but it's easier to get. I also put some threaded rod
pieces in it for reinforcement. When it was dried thoroughly I coated it
with epoxy a couple times. The best thing about this lap is that you can
strip off the pitch with a heat gun and a putty knife without the base
coming up too.
  The other thing I have found is that a full size lap works the edges
more than the center and so I have done all my figuring with a 10" lap
and a 4.5" lap without any turned down edge so far. Good luck,
John

----- Original Message Follows -----
>
> Hi all,
> So it didn't work.  The pitch lap mold is great for 12" and smaller
> but is hard for larger mirrors.  In redoing it I discovered that the
> portland cement between the tiles was coming up with the pitch.  So, a
> brand new can of pitch ruined.
> I guess it is back to TOT with the 10" sub diameter tool.
> Clear skies, Jerry
>
> BTW - my web site is back up.
> http://www.convertabarn.com/Figuring_2.htm
>
>

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