From: "Russell Jocoy" 
To: klowther{at}cisnet.com, tac{at}i1.net
Cc: ATM{at}shore.net
Reply-To: "Russell Jocoy" 






>From: hermit 
>Reply-To: hermit 
>To: Bob Walker 
>CC: ATM Group 
>Subject: Re: ATM Too big, too thin?
>Date: Tue, 25 Feb 2003 19:30:58 -0500
>
>
>Dave Sopchak thinks he was right up against the limit with a 18" X
7/8".
>
>Ken
>
>Bob Walker wrote:
> >
> > I have just obtained an interesting piece of glass.  It's nice plate
>glass
> > 36" in diameter and 3/4" thick with a well finished
edge ... okay, it's
>a
> > table top.  The question is, what should I do with it???  The obvious
>first
> > choice would be to make a 36" mirror out of it.  From my
readings on the
> > List and elsewhere, I tend to think this is impossible.  But, the hope
>that
> > springs eternal and all that impels me to ask, has anyone tried it?
>What's
> > the biggest 3/4" mirror you know of? (Successful one, that is!  Mel?)
> > Another intriguing thought is grinding four 14" or so off-axis mirrors
>out
> > of it.  That has the advantage of being feasible, at least marginally
>so.
> > Then, of course, it could just be chopped up into a number of small
> > blanks -- seven 11 inchers or five 12 inchers plus a 10" ... etc etc.
>Any
> > suggestions on practical ways to proceed will be welcome.  I've got
>plenty
> > of time to mull this over; I don't expect to have my current projects
> > completed for a year!
> >
> >  *  Best regards, Bob
> > *
> >          *           *   *
> >
> >             *         *
>
("atm{at}shore.net")

   Bob,  I just got finished last week cutting a 30" x 69" table
top of 3/4"
plate. When I say cutting I
mean rounding out the rest of my blanks.  In the beginning I was going to
cut a 20" blank out of
the square as my largest diameter. I decided that for 3/4" plate that
16 should be the largest diameter
for digging a hole in. Remember the larger the diameter the longer the
focal lenght, and the only way
to shorten the focal length is to deepen your curve.  If you wanted an f4
with a 36" diameter there
wouldn't be too much glass left in the center with a 3/4" thick blank..
              16" seems to be the limit on 3/4" that I have heard on the
net...

                           RUSS JOCOY...may all your spheres come true
("atm{at}shore.net")

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