I have never heard of a Jigsaw blade that would successfully cut glass.
Robert Hall
www.RobertHall.com
www.RobertHall.com/workshops
www.facebook.com/robert.g.hall
On Mon, Jul 13, 2015 at 10:23 AM, <mark@xxxxxxxxxxxxxxxxxx> wrote:
What I have seems to be working, but it is a mess. Locally I have no idea
where I could get the silicon carbide. It would have to be ordered, but
that is not total road block.
My biggest potential problem I think is going to be cutting the glass to
fit. The glass I am using is left over from another project, and
truthfully I don't remember what kind of glass I used. I have never been
able to get any kind of straight cut with the scoring method. It never
breaks right for me. It looks easy and I am sure its something to do with
the way I apply pressure to break it. Really doesn't matter. What ever
the reason I stink at that.
If it was some form of laminated glass cutting with the right blade and a
jigsaw should be no problem if I take my time. Frame glass and I think it
might work. Might crack, but maybe not. Depends on how much temper was in
the glass. IF its tempered glass its going to be a mess. Gloves and eye
protection for sure and maybe the shop apron too. Will find out fairly
quickly. IF its going to shatter, it will shatter fast, and come to think
of it I may have some glass from an old 4x5 frame laying around.
Appreciate all the help
-------- Original Message --------
Subject: [pure-silver] making ground glass
From: Myron Gochnauer <goch@xxxxxx>
Date: Mon, July 13, 2015 7:46 am
To: Pure Silver group <pure-silver@xxxxxxxxxxxxx>
. . . I went to auto parts store and bought a small tube of valve
grinding compound. That's slow, but it is working.
It is vastly easier if you buy some straight silicon carbide. I don’t
know of any local source for most people, but if you are going to make
ground glass in the future, you should order some from a telescope-making
supply. Here’s one that might do:
http://www.willbell.com/ATMSupplies/ATM_Supplies.htm It’s located in
Richmond, Va.
As you can see at that website, silicon carbide is pretty cheap. And it
never goes bad! I’m still using left-overs from 1962.
I can’t recall what grade I use for ground-glass. I *think* 220 is
okay. I’m pretty sure 80 was too coarse for my tastes, and 400 or 500 was
definitely too fine. You don’t need much, either. 4 oz. will make a lot
of ground glass.
The other thing you need is a “grinding tool”. For 4x5 to 8x10 ground
glass, I use a piece of glass that is roughly 4 inches square and a half
inch thick. The exact dimensions don’t matter. It just has to be big enough
to grip, and rigid enough to transmit even pressure. You can probably make
something out of a piece of plate glass glued to a block of wood.
To grind the glass:
1) Place several thicknesses of newspaper on a sturdy work table.
(Telescope makers often use an upside down barrel so they can walk around
it.)
2) Place the glass-to-be-ground on top of the newspapers. The newspapers
will cushion and “grip” it slightly.
3) Sprinkle a little carbide onto the glass. Keep it in an area a bit
smaller than your grinding tool. You’ll quickly learn how much to use.
4) Sprinkle a little water onto the carbide and place the tool on top.
Move the tool around gently to wet all of the carbide (you’ll feel it), and
then grind back and forth at various angles using moderate pressure.
There’s nothing magic about these motions. Just keep them fairly random and
short enough that you don’t constantly scrape off the grinding compound
with the edge of the tool. With a 4 or 5 inch tool I think I use a
back-and-forth stroke of something like 3 inches total.
5) You may need to add a bit of water from time to time, and in a short
space of time you will feel and hear the grit disappearing (it breaks
down). When it seems like you’re not really *grinding* any longer, rinse
off the glass and tool under running water and start over again with a
fresh charge of silicon carbide and water.
6) Within two or three cycles you should start seeing the glass
beginning to look frosted. Check as you go along to see where it needs more
work, and continue until it is ground and frosted uniformly.
7) If you later decide the surface is too fine or too coarse, you can
regrind it with a different grade, although it will be a little more
difficult seeing how your work is progressing.
The main difference between this procedure and one using automobile
value grinding compound is that this procedure is completely water-based,
so it is much easier to assess how you are doing, make adjustments, and
clean up. The basic idea is the same, though.
Myron Gochnauer
goch@xxxxxx
Got about 15 minutes into it and its clear the glass is grinding down
as it should. I am guessing its going to take at least another half hour
or so, maybe longer to get it like I want, but it is working. Will it be
factory, but from the looks of it I think it will be quite serviceable.
There is something to be said for having done it yourself.
Got to pick up a blade tomorrow that will fit in the jigsaw that will
cut glass. No way I could ever get a clean cut with a typical glass
cutter. Tried a few times and never mastered the scoring, or just never
could get a clean break.
This project is giving me a great appreciation for the work of the early
pioneers. When you see the images they created with equipment that would
be considered primitive, after doing this I can appreciate the work even
more. I have one huge advantage they didn't. I have their experience and
all those that came after them.
A while back someone posted they had a method to shim the ground glass
to make sure that what you saw as in focus on the ground glass was in focus
on the film. Would love to hear the procedure and if they prefer they are
welcome to email me off list.
Slow but sure, and this past couple of weeks have been a pain to find
any time at all to do much of anything. One day when I push the shutter
for the first time, it will all be worth it, at least I hope.
Mark
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