** I must say I like this plan. I will definitely try it. Is there a particular grit that is better or worse? How often do you need to re-do the end of the rod?
The coarser the better. If you entrapped it well, it will last very
long time at slow speed under water.
Leonid Surpin
I have had success using the proper diameter copper tubing as a
’drill bit’…flat on the bottom, and valve grinding compound from an
auto supply store. You grind a hole rather than cut a hole. Add more
compound and flush with water as necessary.
Rob (2nd post)
Leonid the process you describe appears most elegant. It’ locked
into my memory for the day I ever need to drill stone!
Chinese jade carvers used treadle powered spindles with iron tips
and hand-fed grit. The treadle provided an alternate forward and
reverse motion similar to a bow drill. This produced quick results
in skilled hands, as described by John Sinkankas when silicon
carbide grit was being used. I’m sure the Chinese used special
natural grit before then. Cutting with grit and metal remains the
most basic and effective method, the bottom line, as used in ancient
times and easily available today.
All except the time factor. Today we expect the fastest results.
Alastair
I seriously doubt this will help. Any commercial glass product that would have formed sea glass would have been properly annealed
So you’re saying that getting knocked around the ocean floor
wouldn’t affect the stresses one way or the other, only the
manufacturing? Once annealed, always annealed, unless heat is
applied?
Noel
I seriously doubt this will help. Any commercial glass product that
would have formed sea glass would have been properly annealed
So you're saying that getting knocked around the ocean floor wouldn't affect the stresses one way or the other, only the manufacturing? Once annealed, always annealed, unless heat is applied?
Yep pretty much. Glass is not metal so even thought the same term is
used the stress is not from cold work but heating or cooling too
rapidly across the stress point temperature of the glass.
Jim
James Binnion
James Binnion Metal Arts
James,
But I seriously doubt this will help. Any commercial glass product that would have formed sea glass would have been properly annealed during manufacturing. Insufficiently annealed glass will spontaneously crack very rapidly after manufacturing it.
I’m not so sure about this. I used to design showcases and worked
with glass suppliers at the time. I could well be wrong, but as I
remember what was explained to me, is that the glass is annealed
during manufacturing, only to prevent cracking not necessarily to
completely stress relieve it. I could again be wrong, but we had
pieces heat processed for various reasons before using them. I do
remember observing the workers lightly grinding the surface of the
glass on both sides where they were going to drill a hole, before
drilling. I thought they did this because there was a possibility of
stress right along the surface of the sheet, even after annealing or
tempering.
Dan Culver
As glass cools from its liquidus the quartz ib it goes through a
change of crystal structure and unit cell size. This is called
cristobalite squeeze and occurs at about 600 deg C. Annealing should
be doen at a lower temp than this, 500 deg C being normal. The mass
of the glass determines how long you should anneal for, small pieces
of sea washed glass will only require about 10 minutes, a 2 kilogram
block will take 24 hours or more.
However, I doubt if it will make the slightest difference as the
broken sea washed glass will be stress free otherwise they would
have never got to be how they are. peripheral speed on the drill is
the critical bit for fixed abrasive tools.
Nick Royall
the glass is annealed during manufacturing, only to prevent cracking not necessarily to completely stress relieve it.
I was probably over simplifying a bit as I am assuming the sea glass
is mostly bottles and jars which are going to be as stress free as
possible. My experience with glass is fairly limited having only
done a small amount of glass casting so I am no expert. But like
metal there are various heat treatments use for achieving different
properties. I think for plate glass like you were working with there
might be a desire for a little more stress to give strength but I
would certainly defer to someone with more experience.
James Binnion
James Binnion Metal Arts
So you're saying that getting knocked around the ocean floor wouldn't affect the stresses one way or the other, only the manufacturing? Once annealed, always annealed, unless heat is applied?
Any stresses which might be present would be relieved by that
knocking about. In the usual manner for glass, by breaking.
Al Balmer
Sun City, AZ