Last ditch attempt at reclaiming a damaged unit:

I have a water steriliser for a garden pond. It consists of an
ultra-violet fluorescent tube, which passes through a larger chamber
through which water is pumped.

The fluorescent tube is separated from the water by means of being
contained within a test-tube shaped quartz glass tube, about a foot
long and an inch-and-a-half wide, the wall thickness being
approximately 1mm (sorry to mix metric & imperial measurements.. I was
brought up on the changeover!)

cutaway view, side-on:

 water                     water
 inlet                     outlet
__| |________________________| |_
|            water               |
|    /'''''''''''''''''''''''''''''
|   |      ========================<---------- fluorescent tube
|    \.............................<---------- glass 'test tube'
|  water                         |\
'''''''''''''''''''''''''''''''''' \___damaged lip of 'test tube'

Now, my problem is, that whilst cleaning the innards of the unit, the
'lip' of the quartz glass 'test tube' became damaged - a piece being
chipped off the rim. This means that the tube no longer seals in it's
mounting, which is a rubber 'o' ring lining the inside diameter of a
hole at one end of the unit's casing - water can pour out at the end
via the chipped portion of the tube.

What I'm wondering, is that since there is plenty of spare length on
the quartz tube, could I repair the unit by slicing off the end of
said tube - so that the open end of said tube would once again seat
correctly in it's rubber-lined hole at the end of the casing?

Specifically, I remember a method of making 'attractive ornamental
glass rings' from a childhood arts and crafts book. As I remember, the
method involved filling an old glass bottle with oil, and then
plunging a red-hot poker into the oil. The result was supposed to be
that the bottle cracked cleanly around it's circumference, at the
level of the oil's surface. You then repeated the process to produce
your glass rings.

I'd like to know if I can employ this method to take off about 1cm
from the end of my tube, removing the damaged section, and leaving a
clean, level rim. What would be
the procedure - is oil the correct thing to use, should it be
pre-heated, should the glass be pre-scored where the break is intended
to occur? Is there anything else I should do to try and ensure best
results?

If information you supply results in my reclaiming this unit, a tip
will be in order. If not, and things go 'pear-shaped', nothing's lost,
I shall just have to replace the full unit.

If you need question clarification please ask, I'll be paying
attention.

Thanks for your time.

---

Clarification of Question by gan-ga on 30 Dec 2002 16:32 PST

Here are the searchterms I've already tried on Google, whilst trying
to find a reference to this method of cutting glass:

"will crack around the"
"the glass will crack"
"the glass will crack cleanly"
glass bottle "crack cleanly"
glass hoops
"glass hoop" crack
"making glass rings"

couple of possible searchterms not tried yet before I go to bed:
from
http://www.kimble-kontes.com/pdfs/glass_fabricating_terms.pdf
thermal shock
local temperature shock
crack-off

---

Request for Question Clarification by sublime1-ga on 30 Dec 2002 19:45 PST

gan...

I find no references to the particular method you describe.
Are you set on doing it in this manner, or will you accept
alternative methods as an answer?

sublime1-ga

---

Clarification of Question by gan-ga on 30 Dec 2002 21:03 PST

Hello Sublime-1,

Sure, any method will do, that I can employ using readily available /
fashionable tools &/or jigs - all I need is to get back to a fully
perpendicular 'end' to the tube, without the missing chunk. If
possible I'd like to avoid going to the lengths of having it cut
professionally; I'm guessing that would be prohibitively expensive?

I've had a flying crack at the oil / hot poker method & must admit,
doesn't seem to work on a wine bottle, at least. I did think about
trying an angle grinder but stopped myself in the nick of time ;-)

gan...

I believe the following tool will be more effective
than an angle grinder, and I hope it falls within
your definition of "readily available". Item 79022,
on the following page, is a glass cutter designed 
to cut tubes of up to 1.5 inches in diameter, and
is available from the Wheeler-Rex Company:
http://www.wheelerrex.com/glass_cutter.html

I don't see a way to order online. 

Contact info:
Wheeler Manufacturing - division of Rex Int'l USA
P.O. Box 688  
3744 Jefferson Road  
Ashtabula, OH 44005
Ph: 440-998-2788  
Fax: 440-992-2925  
Toll Free: 1-800-321-7950


KHUE.com offers a variety of stained-glass and
glass-related products, including the bottle 
cutter on this page:
http://www.khue.com/dept/cutt/bott.htm

While the bottle cutter itself might be a bit wide
for your purposes, the instructions for its use
are very relevant to your situation. The instructions
start here:
http://www.khue.com/dept/cutt/bott1.htm

It continues with instructions for etching the
glass, using a very light etch, and only one
revolution. The next step outlines heating the
etched line with a candle, followed by cooling
it with an ice cube, which causes the etch to
become a crack, allowing the piece to be easily
removed:
http://www.khue.com/dept/cutt/bott3.htm

These procedures, in combination with a cutter
such as the one above, should make it a 'snap'
to cut your tube. If you are not willing to 
wait while the cutter above is delivered, you 
might even find a way to use a regular glass
cutter, assuming you can find a way to stabilize
the etch through some alignment process as 
might be used on a table saw, e.g.

Perhaps you could hold the glass cutter in a
vise, and find some means of rotating the tube
against it with adequate stability to produce
a straight line around the tube. You could 
practice on bottles until you got it down pat.

I'm not sure, but perhaps the process and the 
results would be improved by the use of glass
cutting oil available on the KHUE site here:
http://www.khue.com/dept/chem/cutto.htm

Presumably, this reduces splintering on a 
microscopic level, and produces a cleaner etch.
Maybe 3-in-1 oil would work just as well?

Please do not rate this answer until you are satisfied that
the answer cannot be improved upon by means of a dialog with
the researcher through the "Request for Clarification" process.

sublime1-ga


Searches done, via Google:

glass tube cutter
://www.google.com/search?num=50&hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=glass+tube+cutter

glass cutting tube
://www.google.com/search?num=50&hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=glass+cutting+tube&btnG=Google+Search

"glass cutting" tube
://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=%22glass+cutting%22+tube

Useful answer! I've some old carbide lathe turning tools somewhere
which'll serve nicely to score the glass, & I'm sure I can rig up a
jig from scrap to keep the scored line true. Candle and ice cube..
worth a go! Thanks for the above info.

I am familiar with small glass tubing, such as neon lights and  small
lab tubing, where typicaly the tube is scored with a file and snapped,
but this is probably not that simple with a larger diameter, and
quartz glass has some different properties.

You might however check at a local Neon sign shop, where there would
be some experts at handling glass tubing
  
Also - found this site, and some alternatives
http://www.geocities.com/heartland/village/3131/uv.html

gan...

I just gotta say Kudos on the creative graphics!