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Re: [ATM] [offlist] New Tool?

Re: [offlist] New Tool?Thanks, Stan. Does that mean that instead of my stroke going 2" over the edge in each direction it should go 3" over the edge for grinding and 2 5/8' over the edge for polishing? (for a 12.5 inch mirror)

  By the way, I have already perforated the mirror with a relatively small diameter hole. I plan to mount the Nasmyth tertiary mirror on a rod through the hole to increase ease of alignment and to avoid another spider vane.

  My wife & I loved Maui when we were there for our 25th anniversary a number of years ago.
  John
  ----- Original Message ----- 
  From: Stan Truitt 
  To: John K. LaShell 
  Sent: Tuesday, March 20, 2007 7:33 PM
  Subject: Re: [offlist] New Tool?


  [offlist]




    Hi, Everybody.
    I'm working (slowly) on a 12.5" alt azimuth Gregorian. I plan for the focus to come out through the altitude bearing. I am almost done rough grinding with a tile tool. (I had to put a second layer of tile on it a while back.) Here is my question. The tool is 9.5 inches in diameter. Should I keep on using it or should I make a new tool the same diameter as the mirror? If I use the 9.5 inch tool, what kind of stroke should I use to get a spherical surface without a turned down edge?
    John LaShell
    P.S. The reason I'm making a Gregorian is that I don't want to attempt a convex secondary such as a Cass. uses.


  Aloha John,


  Greetings from Maui!


  Adjust your grinding stroke length, increasing it (radially) by about an inch. For polishing, work a bit more slowly and increase the stroke by about 5/8ths, radially.


  Taking your focus out Nasmyth style also avoids perforating the primary, and that pesky turned edge around the I.D.




  Best regards,


  Stan
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