Re: [ATM] Polishing to a sphere

[Mike Lockwood <melockwo@uiuc.edu>]

Gil,

Gilbert Gagne wrote:
> I thought my turned edge had gone but a Ronchigram outside of focus 
> brought it back!
> http://www.atmlist.net/contrib/ggagne-at-clearwire-dot-net/14-4out.jpg
> 
> I also took a Ronchigram with only one line showing, per Ken Hunter, and 
> it shows roughness and a slight central depression.
> http://www.atmlist.net/contrib/ggagne-at-clearwire-dot-net/114-1bar.jpg
> 
> My next step is to redo the lap with softer pitch to work with these 
> cooler FL winter temperatures.
> Thanks to everyone for the helpful comments.

In my experience, unboiled natural linseed oil does better at 
softening pitch than turpentine.  It does not evaporate out nearly as 
quickly, so the pitch does not get harder as quickly.  I notice only 
very slight hardening (if any), and I use laps for months.

As far as spherizing, my short article on that subject may be helpful:
http://bi-staff.beckman.uiuc.edu/~melockwo/mirror_making/oblate/oblate.html

Nice to see someone looking to go to softer pitch for spherizing 
rather than harder!

	Mike Lockwood

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