Re: [ATM] figure stroke ten inch

[Mike Lockwood <melockwo@uiuc.edu>]

Hi,

Tom Fredrickson wrote:
> I'm working on a 10 inch mirror full size lap. I turned the edge and
> went to work with short coc strokes to clean it up. Now I need to add
> correction to the edge. I have been working the edge and it is going
> the wrong way. I feel I need to work the center and make it deeper.

As you can tell from the widely varying advice you've received on the 
list, there are many ways to make a mirror.  Allow me to submit my two 
cents worth......

A 10" F/5 should be able to be figured with a full-size lap if the 
pitch is soft enough.  If the pitch is not soft enough, you will get 
to a point where the mirror just won't correct anymore, and if you 
force it, bad things may happen.

The pitch can be made softer by warming it or working in a warmer 
room.  This should get you to full correction.

I'm not sure if you've read my full-size lap figuring page, so here's 
a link - hope it helps:
http://bi-staff.beckman.uiuc.edu/~melockwo/mirror_making/full_lap/full_lap.html

What I say there will also help you judge the hardness of your pitch, 
which is key in this situation.

If you have made other mirrors and are ready to try subdiameter laps, 
this mirror would be a good one to start learning on.  I would use a 
6" lap, personally.

	Mike Lockwood

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