Re: [ATM] artificial convex curve for pitch lap

[Ken Hunter <atm_ken_hunter@yahoo.com>]

First off... 
   
  Do away with all the paper stuff. It will only give you grief slipping and sliding all over the place under your lap. Then get rid of all the plywood (even the good stuff isn't good enough). 
   
  Once you get the curve made in the glass, pour a cement, dental plaster or similar tool (upon which you will pour the pitch for the tool) using the curve in the glass as a mold for the tool. Directions are all over the I'net for doing this.
   
  Really simple and stable PLUS... less expensive and time consuming than any other method.
   
  Ken Hunter
   
  

jeff newsom <triolian@earthlink.net> wrote:
  Howdy folks-
This one's probably over the top but......... 
So,I've got a 14.5" piece of glass ,with an f/5 curve(hypothetically,soon to be a reality). This is approx as I'm not allowing for the bevel . I'm making the pitch lap base ahead of time out of layers of baltic birch(the good stuff! shite!) and the diameter is 10.5" . I'm using layers of poster board to simulate the convex curve. I've figured the sag roughly to be .181 and with a micrometer figured the number of pieces of poster board I'd need to be about ten.I've cut smaller and smaller paper discs all roughly 1/4 smaller than the previous one. But this is obviously building up the central region too much.Now I'm guessing it probably won't matter that much after I poured pitch over it and pressed it, but how could I determine more accurately the different disc diameters?????? Thanks---JN
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