From: John Lynch 
To: Ricardo Dunna , atm 
Cc: john_p_lynch2003{at}yahoo.com, John.P.Lynch{at}nasa.gov
Reply-To: John Lynch 


Ricardo,

I built the Twyman viscosity tester described in Texereau to make pitch
laps for a 6" f/6 mirror. It's a good tool to have because my laps
were pretty consistent.  I think that's 14 degrees total angle. And, don't
forget the 0.04 flat spot on the end. Also, I used 5/16ths inch steel rod
that was attached to an evaporated milk can, filled with machine nuts to
weigh exactly 2.2 lbs.  If you can find some bathroom fixtures with
thin-walled brass 3/8th inch tubing, I found that the steel rod fits nicely
through this as a support.  You might also want to consider the Texereau
method for pouring pitch lap strips and cutting squares out of them;
remember to cover the wood base and separators with aluminum foil to keep
the pitch from sticking.  Good luck!

Regards,

John Lynch


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