From: "Frank Q" 
To: "CSC" ,
        "Atm" 
Reply-To: "Frank Q" 


Hi All

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.

The positioning of this groove is critical - it has to be exactly where you
want to split the blank as it is the guide for the rest of the cutting
operation.

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.

Final comment - if the wire is thin (about 1 mm = 1/25") then the
groove should not be much wider than this, so your blanks should be thicker
than the 1.38" you mentioned in your posting.

Anyhow, that's my suggestion. I can see a few problems with it but they can
be overcome with a little imagination.

Keep us posted on your progress.

Cheers

Frank Q

----- Original Message -----
From: "CSC" 
To: "Atm" 
Sent: Wednesday, December 11, 2002 4:13 PM Subject: FW: ATM thick mirror blanks


>
>
>
> -----Original Message-----
> From: CSC [mailto:optic{at}gwi.net]
> Sent: Wednesday, December 11, 2002 12:32 AM
> To: Jerry B. Hillman
> Subject: RE: ATM thick mirror blanks
>
>
> Our club has two 16" x 3" thick blanks.  It is old Pyrex,
originally cast
> for a reference flat.  It has a shallow machined groove in the back which
> been flattened, and is blanchard ground fully in front.  There are some
> seeds, etc which might show when you grind in your saggita. We were asking
> $500 at S'fane with no takers. That's half the United Lens price for new
> Pyrex. Whaddya bid?
>
> I'm looking for a way to split one into two 1.38" thin blanks, myself.
I'm
> tired of thick stuff.
>
> Colin
>
> -----Original Message-----
> From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of Jerry
> B. Hillman
> Sent: Tuesday, December 10, 2002 6:33 PM
> To: atm{at}shore.net
> Subject: ATM thick mirror blanks
>
>
>
> Hi all,
> Anyone got a source for thick pyrex?  Reply off list please.
> I need a large pyrex mirror blank. My 10" isn't big enough.
> Clear skies,
> Jerry
>
>
>

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