Re: [APD] Cutting Glass -- or - Cracking the Method of Parting Crystals

["S. Hieber" <shieber at yahoo_com>]

Are you talking about straight cuts or curved cuts?

Glass loves to crack, it wants to crack, it's crystal
structure makes it ready and waiting to crack, longing to
crack -- it just needs to be told where to crack. That's
what a hand-held glass cutter does.

3/16" Single plate glass is petty cheap from a glass store
and might be worth considering rather than trying to
disassemble an old aquarium.

Get some 400 wet/dry silicon carbide sandpaper to dress the
edges afer cutting. This makes the razor sharp edge
something much less dangerous.

When I worked as a tile layer, many years ago, we wouldn't
dream of using our tile saws on anything but the intended
material -- the blades were just too darned expensive to
possibly mistreat. Otoh, a diamond dust impregnated tile
saw blade will cut just about anything rigid even though
they won't, in most cases, cut soft material. It will cut
ceramic bisque. It will cut your thumbnail but it won't
easily cut your thumb -- in most cases, but it will in some
cases so don't try this at home folks. Keep the blade and
the work material cool with plenty of water. The blades are
easily warped and having them "retensioned" is costly.
Trying to turn the work material during a cut or use the
side of the cutting edge -- for example to try to smooth
out a curved edge -- can easily warp the blade. And, of
course, you probably know that, if the motor slows down,
you're feeding the material too fast.

You can make large curve cuts by making repeated straight
cuts along the intended final curve. Some silicon carbide
wet/dry on a belt sander can quickly take the down the last
"bumps" and give you your final curve. But unless you're
doing this "grinding" with a tool made to work with water,
the electrical shock hazard is high. And without using
water, you need to take great care about the microscopic
glass dust that you will be creating. Whatever you inhale
will might never leave our lungs! And what dust gets on the
work surface, bench, etc. will probably eventually be
inhaled unless cleaned up properly. So a hepa filter
vacuum/dust-collector is appropriate.

A silicon carbide rod saw in a hack saw frame can sometimes
be used to make curved cuts but the material must be
especially well secured to prevent cracking. And it's very
slow going and difficult to stay "on the line" because a
rod isn't self-guiding the way a flat saw blade is.

I recommend that you let curved cuts be done by a
professional glass shop.

If you're just making straght cuts, I'd just use a good
quality hand held glass cutter from glass shop or other
reliable source of good tools -- they are relatively
inexpensive. A little bit of skill is required but it's not
too difficult. The most common mistakes novice cutters make
is trying to cut too large a piece or too small.

Gentle cruves can also be accomplished with a really good
hand-held cutter but it takes more skill and a bit more
luck. 

A cheap hand-held cutter will make you curse that glass was
ever invented. A hand held cutter is faster than any kind
of sawing and very effective (also great for acrylic
"plexiglass" sheets too, btw, but not for polycarbonate).
It tells the glass what it longs to hear, where to crack.  

Do your layout with a grease pencil or felt pen (on glass
but not on acrylic). Do the cuts that will have the largest
"remains" first and work down to the continually smaller
pieces. Avoid really large sheets if you can; have the
glass shop cut those down for you into smaller stock that
accomodates your intended layout.

Don't forget to wear strong gloves, long sleeves, and an
apron until the cutting and edge dresssing is complete.
When considering the gloves, etc, ask yourself the question
woodworkers ask themselves when adjusting the height of the
saw blade, "How deep a cut into my flesh am I willing to
consider acceptable?" There's only one good answer and you
should focus on achieving that goal.

And remember, if any job is terribly difficult, either
you're using the wrong tool, a badly made tool, or using
the tool the wrong way."

Sorry about the pontification but I hope some of that
helps,
Scott H.

--- Steven Pituch <spituch at ev1_net> wrote:
> Hi all,
> 
> I need to make some glass covers for some of my tanks
> that are being used as
> green houses for growing plants emersed.  Of course I
> would never dream of
> using a glass cover on any of my aquariums.  I have never
> successfully cut
> glass to shape using a cutting wheel or any sort of
> device that scratches
> the glass.  I have a water cooled ceramic tile saw that
> works pretty well.
> I have even cut two inch thick stones to shape them to
> fit in my aquariums.
> 
> What I would like to do is either buy some used glass or
> old aquariums and
> use the above saw to cut the glass.  Has anyone ever done
> this before?  I
> would be using whatever glass is available cheap whether
> it was regular
> glass, plate glass, or tempered glass.
> 
> Any advice is appreciated.  Yes, I need to be cheap at
> this time.


=====
-  -   -   -   -   -   -   -
She Wrote the book on low maintenance aquatic gardening!
Diana Walstad, author of _Ecology of the Planted Aquarium_
Meet her at  - The Fifth AGA Annual Convention
Details & Registration at www.aquatic-gardeners.org & www.gwapa.org


	
		
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