On Jul 3, 10:58*am, Gerry wrote:
On Jul 3, 1:08*pm, James Waldby wrote:



On Fri, 03 Jul 2009 09:31:33 -0700, Gerry wrote:
On Jul 3, 11:05*am, "David Courtney" ... wrote:
* * You could try going to a flooring/ceramic tile store and ask for
* * some scraps of granite, slate, marble, and limestone tile.
* * Use a 3" diamond hole saw to make disks that you could set at
* * various levels in your concrete cores?

"Gerry" wrote ...

[...] Next phase is to make cores for it to drill through,

simulating different type and layers of formation. Been playing with
parrifin and cement combination but am looking for other ideas, like
maybe some epoxy/aggragate that will offer different drilling rates.
Bit is a 1" masonry bit, turning at speeds below 150 RPM. Cores are
made up in 3" PVC pipe with a 1/8 hole cast through the center to
provide a flow path for water to carry cuttings from hole. Any ideas
for core materials will be appreciated. Thus far I have used
cement/sand with varying levels of cement, and wax with bentonnite or
sand. Both work but I need more hardness to vary drilling rates

Thank you-all good suggestions. Because this is to be used in a
classroom and Profs are in a hurry to be able to show different
formations and their rate of progress I cannot go with materials that
are too hard to penetrate in a short time. Also, I am somewhat limited
to 50 to 75# weight on bit because all the top drive and carriage weighs
is 51#.
[...]
I'm thinking fiberglass with sand as an aggragate may be worth playing
with. Perhaps with pieces of paver tile or slices of brick embeded in
the core as well. Maybe some ole pieces of transite siding if I can
still locate some. Whatever I use has to have a 1/8' hole through it to
allow my drilling fluid to come from the bottom to the top. Just too
much work to use hollow drillbits and tubing to allow circulation from
the top like a real rig.

Perhaps make up some sand/vermiculite/perlite mixes, bound
with sodium silicate ("water glass").
http://en.wikipedia.org/wiki/Sodium_silicate
I've seen molding cores that I think were made up with sand and
sodium silicate hardened by CO2 exposure, that were a little
softer than most sandstones.

--
jiw

Waterglass-have not heard that name in many years. Where would I find
sodium silicate now? Any ideas?

Used to be able to order it at drug stores.
Karl