Ken, this sounds like some type of tempered glass. I recall a
highschool assembly put on by, I think, GE. This was in the 1950's.
They demonstrated pounding a large spike into a wood timber using what
appeared to be a common flask from a chemical lab. Then when done,
just dropped a piece of carborundum into the flask and it shattered.
Very impressive!

Do you have the ability to aneal the glass tube? Then try one of the
cutting methods mentioned in other posts.

Paul

(Ken Sterling) wrote in message ws.com...
On 24 Jun 2004 15:07:00 -0700, (pragmatist)
wrote:

(Ken Sterling) wrote in message ws.com...
Gang,
Got a piece of glass tubing (similar to Pyrex) which is .490 ID,
.625OD and I need to cut a piece about 11/16 long. File won't touch
it, glass cutter won't do it, have been trying to score the outside
with a thin "cutoff wheel", which scores it, but the stuff won't "snap
off" as expected... just shatters, even past the score mark. Am I
going to have to cut completely through with the cutoff wheel to do
this?
Ken.

Old Glasscutting trick, works on 'flint glass`, :
(Might work on pyrex even with its lower coefficient of expansion).
Once you've got it scored wet the score mark with water.
Then touch the score mark at one point with a red hot piece of
metal, (large nail, etc.).
The thermal expansion does the cracking.
Reportedly, turpentine works better, or is this just an old grandad's
tale. He always dipped his cutting wheel in turpentine before scoring
the glass.
Gerry :-)}
London, Canada
Just as an update.... I've tried a few different suggestions (with not
much luck), even tried, just for the sake of it, the engraving tool
with carbide point.... it would score the glass but I still couldn't
get a clean break that I could dress up for finish. This is a
borosilicate glass tube from McMaster Carr. I haven't tried the "hot
rod/wire" as of yet, but nothing else is getting the job done. I may
have to take it to someone with the proper equipment. Another poster
questioned length - it is going to be eleven sixteenths (spelled for
clarity, although a decimal would have worked G). I have tried
several methods of "scratching" the outside - not much success. I'll
succeed, but it may be due to someone elses help :-)
Thanks to everyone for all the posts. I'll post a followup shortly.
Ken.