From: 
To: Frank Q 
Cc: tkrajci{at}san.osd.mil, atm{at}shore.net
Reply-To: 


A bunch of decades ago, I saw a setup something like this at some cathedral
in France (Notre-Dame de Paris, I think) where they were cutting stones to
replace old ones. I recall that they had a continuous cable that ran on
pulleys and had springs to maintain tension and a water slurry or something
to do the actual cutting; it was used to cut the stones, as I said.
Whenever I visted the place the machine was running constantly. But again,
the memory of a 9-year-old, 43 years later, is not necessarily too
reliable. I don't remember if they cut from the top or from the side, but I
think that the cable ran in one direction rather than going back and forth.

Guy B

On Fri, 13 Dec 2002 10:02:12 +1000 Frank Q  wrote:

>
>
> ----- Original Message -----
> From:
> To:
> Sent: Friday, December 13, 2002 3:24 AM
> Subject: Re: ATM Splitting thick mirror blanks
>
>
> >
> > > From: "Frank Q"
> > >
> > > Here's my suggestion at splitting the 3"
> thick blank into 2 x 1.5" thick
> > > blanks...
> > > Grind a groove around the cylindrical
> surface of the blank....
> > > Put the blank on a grinding table and put a
> length of thin wire in the
> > > groove.
> > > The wire should go around about 75% of the
> circumference - that way the
> > > operation takes less time and more
> importantly, it will cut through the
> > > blank
> > > exactly where you want.
> > > Put some tension on the wire, spin up the
> grinding machine, feed grit
> into
> > > the
> > > groove, turn off your brain etc etc etc....
> > >...Anyhow, that's my suggestion. I can see a
> few problems with it but
> they
> > > can be overcome with a little
> imagination....
>
> >
> /*****************************************************/
>
> > As you cut with the wire into the glass
> (while the table is
> rotating)...you
> > cut a deep groove into the glass.  As the
> groove gets deeper, you have a
> > heavy, unsupported 'shelf' of glass, putting
> more and more stress on the
> > smaller and smaller section of uncut glass.
> How do you support the glass
> > shelf, while also allowing the glass to
> rotate?  The wire and 'shelf
> support'
> > would interfere, no?
> >
> > As I see it, you may have to keep the glass
> stationary, and move the wire
> or
> > other cutting blade in a back/forth motion.
> Then you will be able to
> support
> > the growing 'glass shelf' without interfering
> with the wire/blade.  Or is
> my
> > imagination letting me down here?
> >
> > Tom Krajci
> > Tashkent, Uzbekistan
>
> /******************************************************/
>
> The intention is to ROTATE THE GLASS so that
> the wire grinds its way
> evenly towards the centre of the blank. That
> way you will have a disk
> supported AT ITS CENTRE by a cylinder of uncut
> glass and so it
> will be balanced.
>
> My GUESS (I say again "GUESS") is that for a
> 16" blank, when the
> central "support" gets down to about an  inch
> or so, it will snap cleanly
> across.
>
> Do you see what I am trying to say ?
>
> I shudder to think how long this operation will
> take.
>
> PS If I remember correctly, the device used to
> cut holes in glass is/was
> called a "biscuit cutter" (and I have had lots
> of fun with those). Maybe
> we could call the above technique a "cheese
> cutter" as it reminded me
> of the wire contraption found in the kitchen
> used to cut cheese !!
>
> Cheers
> Frank Q
>
>
>

--- BBBS/NT v4.00 MP