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Diamond setting in rock/helicord?


Dear George Fox, What is a heloicord that you mentioned for
setting diamonds in stone…from the back??? Doesn’t Mary Ann
Scheer set diamonds in stone or is it carrie adell???
Thanks calgang



I think that George (correct me if I’m wrong) meant a heliocoil

  • machine shops/mechanics use these things to repair damaged
    threads. Basically it is a piece of steel wire of the same pitch
    as the thread wound in a spring like fashion and formed to give
    the correct shape for a standard thread (vee shaped). In a thread
    repair the damaged ones are drilled out and then re-tapped to the
    diameter of the outside of the heliocoil (the inside of the
    heliocoil is the size of the damaged thread). A special tool is
    used to insert the heliocoil (a healthy dose of Loctite as well
    usually). They can be used in a blind hole as well.

Where they would be useful for settings is that one could be
epoxied into place in the stone to give a threaded rod attached
to the setting a place to call home.

One method not discussed yet is electroplating the inside of the
hole in the stone to get a metal base to form the setting from.
You can build a pretty healthy layer of metal up pretty quickly
on rocks (I have experimented with this as a means to putting a
inexpensive copper bezel on small agate slabs - worked great
except the plating solution etched the agate). Just a though on a
another way of approaching the problem.

On this topic as well - unless you plan on drilling a lot of
holes in rock a diamond core bit (the larger diameters) is a
pricey investment. A cheaper method although slow and very boring
(pardon the pun) is to use a piece of tubing - steel, brass or
copper, in a drill press using silicon carbide grit slurry. Based
on pratical experience - a 3/4" hole 1" deep in nephrite jade
took about 4 hours of standing at the drill press. The hole will
have a slight taper shape to it as the pipe will wear a bit more
on the end. Diamond grit may speed the process up but costs more.
If the hole is small you can also use a flexshaft with a diamond
burr (and lots of water) but getting it accurately round may be
fun. Best thing to do is find a willing local Lapidary. We enjoy
(?) doing this sort of thing.

Cameron Speedie
Island Gem and Rock


hi calgang,

a helicoil is a coil of tempered steel. it is used to put screw
threads of surprising strength into materials not meant to
threaded, or to repair stripped screw hole threads.

my suggestion to use them to set diamonds in granite was not
well thought out. it is posssible, but a lot of trouble and would
wreak havoc on the helicoil tap.

i’m not sure who you are refering to in regards to diamonds in
stone or what technique they may be using.

best regards,

geo fox

 . .Best thing to do is find a willing local Lapidary. We
enjoy (?) doing this sort of thing. 

Don’t know if “enjoy” is the right word; it can be satisfying.

Some years ago, my husband ( elec. engineer) told me of a fellow
engineer working on developing a piece of test equipment which
required the shielding of a wire or cable from electromagnetic
interference. He had a 3" dia x 1" thick disk of the shielding
material (metal impregnated ceramic or ?) but the machine shop
said they could were not allowed to drill it for him.

My husband asked if I could do it? Certainly–I love a
challenge. Used a diamond drill in flexshaft, shallow container
with water level just over top surface. Took some time, but very
effective and no breakout. The engineer not only made the
equipment, but recieved a nice monetary award from the company –
he made it possible to perform needed tests and saved them
thousands of dollars when additional equipment capital was
unavailable to their department.