Re: [ATM] Grinding questions

["Stuart Hutchins" <stuart452@earthlink.net>]

John,

Nate's advice is good.  All mirror making literature emphasizes learning the
techniques of glasswork on a 6 or 8 inch relatively long focal length
mirror.  I have forgotten from your previous posts what F ratio you are
trying to make, but anything below F/5 becomes progressively more difficult
to figure and to test using Foucault. Even your sphere will need to be
figured to get it right.

But with luck, a reasonable sphere will come out of polishing.  Since you
will figure a sphere, not a paraboloid, the task is easier, and with
patience and persistence you can succeed.

I have dealt in the past with Bill Hill, one of the sales people at United
Lens.  Phone is 508-765-0500.
They have standardized sizes for small Pyrex blanks.  8 inch dia is 1.38
thick.  You order by specifying material (Pyrex), fine annealed or better,
diameter, and thickness(standard).  For curve generating specify either ROC
or focal ratio.  Blanks from United will be ground flat on the back, ROC
will be approximate +-1 inch, and there will be a slight bevel on the edges.

Hope this helps.

Stuart


----- Original Message ----- 
From: "John Stephen" <atmlist.net@johnstephen.org>
To: "'ATM List'" <atm@atmlist.net>
Sent: Friday, October 08, 2004 11:02 AM
Subject: Re: [ATM] Grinding questions


> What sort of things will places like this need to know, or more
> specifically, what do I need to ask for?  I feel a little intimidated
about
> approaching a serious manufacturer like this (or any others suggested by
the
> group) since I'm just a beginner ATMer.  I'm sure I'll have to know what
> type of glass, the diameter, and the thickness, but how do I ask for an
> initial curve?  ATMer's call it hogging out, but what do the professional
> optical shops call it?  Will they want to know the desired F ratio or SAG
or
> what?  Also, are there any services I'd be wise to ask specifically for
such
> as edging?
>
> In case you can't tell, I'm a mild sociophobe which is why I'm going at
this
> 'alone' with only the web, books, and this group to guide me.  A couple of
> months ago I contacted RF Royce about simply making a finished mirror for
me
> and he declined to make it.  I felt pretty awful about having someone
judge
> me as unworthy of their services (or quality) and don't want a repeat of
> that.  Of course that was sort of a blessing since it put me on the path
to
> making my own mirror which has been pretty cool so far :-)
>
> Thanks,
> - John
> ----- Original Message ----- 
> From: "Nate Jones" <njones@newlintech.com>
>
> > I have used (3) United Lens Co. Pyrex blanks and they turned out
fabulous.
> > I have also heard that Willman-bell kits are nice because they give you
2
> > blanks (one as a tool) so you could make a plaster tool and then you
could
> > make 2 mirrors (binocular scope??) ;)
>
>
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>


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