[ATM] Re: polishing and figuring a 32"

["Mike Conran" <mike@guidesys.com>]

Fabio Falchi writes:

> Dear friends,
> it is quite a while that I don't post and I've also changed e-mail address.
> To cure our aperture fever we bought from Reginato (www.reginato.it) a 80 cm (nearly 32") pregenerated pyrex blank. It is ready for polishing. We have a 46 cm (18") tool.
> My question are:
> - what are the movements (pattern) the tool has to follow in polishing?
> - what are the movements (pattern) the tool has to follow in getting a parabola?
> In the past we used only full diameter tools to polish, so we are at the first experience with a subdiameter tool.
> I know that for the US standards a 32" is not BIG, but here in Italy it is.
> Fabio Falchi
> _______________________________________________
> ATM mailing list http://www.atmlist.net/

Fabio, 

That is considered a big scope in the US too. 

What is the focal ratio intended on the mirror?  I ask that because if it is 
a short one, you will likely need to use several small tools to parabolize.  
Not difficult to do, really as the small tools will allow you to localize 
polishing actions in figuring. 

Will you be using a machine to grind and polish?  The 18 inch tool will work 
just make your grinding and polishing stroke long enough to cover the 
mirror's diameter.  I am assuming you will do the work mirror face up, TOT. 


Mike Conron 
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