LAPIDARY DIGEST
Administered by Hale Sweeny (hale2@mindspring.com)
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This list digest contains the following message subjects:

1. LapDigest News for Issue No. 82 - Tues 11/11/97
2. SPECIAL: Manufacture and Use of Synthetic Diamonds
3. SPECIAL: Making Diamond Tools
4. SPECIAL: Make Your Own Plated Laps
5. SPECIAL: Home-made Extender for Diamond Compound
6. SPECIAL: Table of Diamond Powder Sizes as Sold


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<MSG1>

Subject: LapDigest News for Issue No. 82 - Tues 11/11/97

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PLEASE NOTE: We have NO queries or responses for the next
issue. If you have a query or a response to a prior query,
please send it to lapidary@mindspring.com now. The next issue
will appear when queries or responses are received!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This will be a different issue from any other issue we have
put out. Everything in this one has come from the internet
or from other net sources. The topic is of interest to me -
- and I hope it will be to you, too.

If you do any cutting at all, it is highly likely that you
use -or will use - wheels or disks or belts with embedded
diamond particles to do the work. We all probably also use
diamond compound - finely ground diamond in a carrier - to do
polishing. I thought you might be interested in some
background on how diamonds are made and how tools might
also be made.

Almost all the diamond you use for cutting is man-made. And
likely, the diamond came from China, for today China is
producing such large amounts of synthetic diamond that their
average price in 1996 was reported to be down to 20 cents per
carat!

When I first started cutting rocks, I bought a booklet with
the title "how to use Diamond Abrasives to cut gemstones" by
A. L. Riggle, Gem Guides Book Co, Baldwin Park CA,
ISBN 0-910652-30-9. It is a good initial guide and I stll
don't know everything included in that phamplet! It was a
good way to get started!

My thanks to all the people who allowed me to use their
material. Hope you enjoy reading it.


hale
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<MSG2>

Subject: SPECIAL: Manufacture and Use of Synthetic Diamonds


Synthesis of diamond was first accomplished in the early
'50s. A method using high pressure and high temperature was
invented by Mr. Tracy Hall.

Tracy Hall finally succeeded on December 16, 1954. In his own
words:

I attempted many hundreds of indirect . . . approaches over
a period of about a year but to no avail, and I was becoming
discouraged. Then, one wintry morning, I broke open the
sample cell after removing it from the Belt. It cleaved near
a tantalum disk used to bring in current for resistance
heating. My hands began to tremble; my heart beat rapidly; my
knees weakened and no longer gave support. My eyes had caught
the flashing light from dozens of tiny triangular faces of
octahedral crystals that were stuck to the tantalum and I
knew that diamonds had finally been made by man. After I had
regained my composure, I examined the crystals under a
microscope. The largest, about 150 microns across, contained
triangular etch and growth pits such as I had observed on
natural diamonds. The crystals scratched sapphire and other
hard substances, burned in oxygen to give carbon dioxide, and
had the density and refractive index of natural diamond. A
few days later, an x-ray diffraction pattern unequivocally
identified the crystals as diamond.

Reference: KURT NASSAU, "Gems Made by Man," Gemological
Institute of America, Copyright 1980.`

Many of you probably recall the announcement by General
Electric on February 15, 1955, that scientists of the General
Electric Research Laboratory had successfully manufactured
diamonds. The crystals were not "imitation" diamonds or
"diamond-like." They were purely and simply diamonds exactly
the same as are taken from the mines of the Belgian Congo. It
must be emphasized that synthetic diamonds are not
"artificial," but are true diamonds by every known test. They
are created under conditions of extreme pressures and
temperatures as are natural diamonds.

Reference: WEBB MORROW, "The Lapidary Journal," December
1963, p. 922

Modern manufacture of synthetic diamonds utilizes these same
methods discovered by Mr. Hall. A mixture of graphite and a
catalyst (typically nickel) is subjected to a pressure of
approximately 1,000,000 pounds per square inch and a
temperature of 1,800 °C for a period of approximately 1 hour.
During this time diamond crystals nucleate at many sites in
the mixture. The mixture is then cooled., then the pressure
reduced to atmosphere. The diamond crystals are then
separated from the remaining graphite and nickel using an
acid wash.

The separated crystals are sorted by shape, size, and
impurities. This process is called grading. A typical
production cycle will yield approximately 300 carat. of
synthetic industrial diamond of various grades. The larger
diamonds are used for sawing concrete, granite, and marble.
Smaller diamonds are used in grinding wheels.

Another use for the diamond crystals is to put a layer of
diamond on a carbide substrate by again subjecting this to
the high temperature high pressure process. This yields a
product called polycrystalline diamond compacts which are
used for oil well drills and cutters for drilling and milling
machines.

Synthetic diamonds are made throughout the world by companies
ranging in size from very small to very large. Because
diamonds are small in size, shipment of the product around
the world does not have a large impact on the price.

Synthetic diamonds are preferred over natural diamonds
because synthetic diamonds can be manufactured to the
specific size and shape required for the given application.
The price for synthetic diamonds ranges from about 10 cents
per carat to 4 dollars per carat, the price depending on
size, shape, and quality. The estimated world market for
synthetic diamonds is approximately 1 billion dollars.

Gem quality and size diamonds have been synthesized using the
same process described above. This has proved to be
impractical at this time because of the nature of the gem
market. However, large synthetic diamonds have been made and
then laser cut into slabs for use as substrate for
semiconductors. Diamond as a substrate has the properties
that are very desirable to semiconductors, i.e. high thermal
conductivity and high electrical resistance. This field of
the industry is growing. Another application for large
synthetic diamonds is bearings. Diamond exhibits very low
friction.

Reproduced with permission of SYNTHETIC INDUSTRIAL DIAMOND
GROUP, ELWOOD® CORPORATION, Oak Creek, Wisconsin 53154 USA
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<MSG3>

Subject: SPECIAL: Making Diamond Tools


(Ed. Note: 'Ketara' had written to Orchid Mail list and said
their class was going to make diamond tools, and asked for
advice. This is one of the responses. hale)


Hi Ketara, You didn't say if the purpose of your exercise was
to develop ways to make diamond tools or if you had a job
that required a special diamond tool to complete.

I'll assume you needed a special tool to complete some job.
You can buy many kinds of plated diamond tools a lot cheaper
than you can make them (faster too).

If, for instance, you need a diamond bit to drill a hole in a
rock, get a piece of copper or brass wire or tube a little
smaller than the diameter of the hole desired. For larger
holes the tubes work better. Coat the end of the wire or
tube with Vaseline (diamond has a great affinity for
oily/greasey items). Sprinkle a very little diamond grit on a
smooth surface. Roll the greased end of the wire or tube
through the grit. Only about 1/8 - 1/4 inch of the tip needs
to be diamond coated. Use modeling clay or putty to build a
small dam around the area to be drilled, leave about 1/4 inch
clearance on all sides of the drill. Start to drill the
hole. After the hole is started just enough to keep the drill
from wandering, put some water in the dam. It should be
pointed out that for this type of drilling, a prill press
works best. It is not necessary to apply much pressure, just
enough to keep the drill in contact with the work.

Check your progress often, allow the bit and hole to get
water. The water is used to cool the drill and work as well
as flushing out the swarf. You may need to add more diamond
grit and water from time to time. Add the diamond grit
sparingly.

If you want to make a flat lap with diamond, start with a
relatively soft metal such as copper. Sprinkle a little of
the selected diamond grit over the surface as evenly as
possible. The entire surface doesn't have to be covered, but
the coverage should be uniform. Use a hard steel roller (an
old steel ball bearing works well) to press the diamond grit
into the copper. Keep a steady drip of water on the lap when
it's in use.

Depending on your requirements, most any soft metal
(something the diamonds can embed in and that will hold them
after being embedded) will work. For flat laps you can even
use plastics. Commercially, diamonds are polished on cast
iron scaifes (flat laps) revolving at high speeds.

These instructions are for using large size (100-600) grit
and removing relatively large amounts of material. They will
result in a 'frosted' appearance on the item being ground.
Finer diamond grits (14,000 - 200,000) are used to achieve a
high polish.
-------------------------------------------------------------
(Ed. Note: The idea of making your own diamond tools is not
new. Sinkankas described, in his book GEM CUTTING, published
in 1984, how to make diamond pointed drills.
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<MSG4>

Subject: SPECIAL: Make Your Own Plated Laps


(Ed. Note: This appeared in Faceter's Digest for 9/28/97 and
is reprinted with his permission . Earlier, Jon Rolfe had
said: <<I used to have custom-plated tools made for my cab
business- Starlite will plate anything you want for $150.00 a
square inch.>>, and someone asked: <<Would you consider
sharing the contact info for this "Starlite"?>> . The
following is Jon Rolfe's response.)


The sales rep who I went through was George Wennerberg at
Magwen Diamond Products. He used to advertise recently in
the back of the LJ. Been doing business with him for 25 years
or so. He was a happy man when I had the production cab
business, but I am not sure how active he is anymore.

<<And I for one would appreciate a more detailed description
of how you do the plating process on your own laps.>>

A prepared disk (Copper plated (cyanide process) of steel is
connected to the (-) terminal of a DC power supply. It is
placed on the bottom of an absolutely level container, on
blocks to level it. The container is filled with Watts
nickel plating solution (240G nickel sulfate, 45G Nickel
chloride,30G boric acid QS 1 liter). A slurry of the diamond
abrasive is stirred and poured into the container, and mixed
and allowed to settle on the surface of the disc. This is the
tricky part...getting it to settle uniformly. Three nickle

anodes are arranged at the top of the tank, at the edges, and
not directly over the disc, and a fourth is suspended over
the center of the disk, where the hub is. Mask the hub with
a resist or tape. They are connected to the power supply
(+). Plate two to four hours at 6 volts at about 1/2 Amp.
Results will vary, and it can be quite trying. If I ever
figure out how to do it better I will post it. I am
beginning to suspect that only the population of diamonds
which are conductive actually get trapped in the nickel, but I
am not sure of that yet.

An easier way is to buy diamond foil. It is brass shim stock
which has been diamond-plated, and can be laminated or even
soldered to a backing disk. I doubt this is how the
commercial lap makers do it because the diamond foil I have
seen has too high a diamond concentration to represent some
the "hobby" style laps I have seen, but I could be wrong. I
have bought so few, who could tell? (grin)

"Jonathan L. Rolfe"
jonr@argo.net
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<MSG5>

Subject: SPECIAL: Home-made Extender for Diamond Compound


(From Facetor's Digest for 10/5/97, with premission:)

Query: <<I lost my extender for my 50,000 diamond compound on
a Saturday evening. Is there a "home-brew" or substitute
that I can use? MarkCase@aol.com>>

Answers From Faceter's Digest for 10/6/97:

..I have used baby oil on occasion and successfully. A very
small amount is needed.
"Mel Albright" <mela@galstar.com>

..Olive oil is sometimes substituted for extender. Peanut
oil would probably work, too.
"Merrill O. Murphy" <momurphy@flash.net>

..I mix Diamond powder which you can buy by the carat with
Vaseline. So You could thin out your compound by mixing with
Vaseline. But it would be cheaper for you to buy Diamond
powder and make your own polish.
"Mark Liccini" <mark@LICCINI.com>

..Years ago, I was advised that the "extender fluid" for
diamond paste is nothing more than mineral oil. I promptly
bought a pint of light mineral oil---and have used it ever
since, with equal results as the extender. A pint of light
mineral oil is cheap---and lasts a long time. Try it.
Merle A. Reinikka" <merle.reinikka@MCI2000.com>

More answers From Faceter's Digest for 10/7/97:

...Speaking about a home brew extender, some months ago
someone on the list suggested using vaseline and 50,000
diamond...I have been using this for the last few months and
have been having very good results and for this tip I wish to
extend a very loud THANK YOU.

I have been dabbing a bit of vaseline on a clean fast lap,
spreading with a razor blade, wiping most of the vaseline off
with tissue and two good sprits of 50,000 (Alcohol and 50,000
one carat mixed) and go to it. Its the best I have tried.
Richard & Barbara Anderson <rlbjanderson@mcn.net>
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<MSG6>

Subject: SPECIAL: Table of Diamond Powder Sizes as Sold:

In the table given below,
Column 1 is micron number as sold.
Column 2 is range of micron sizes in that micron number.
Column 3 is approximate mesh or grit size of particles.
Column 4 is usual use of that micron sized diamond.

Diamond powders are sold by micron sizes. A micron is one
thousandth of a millimeter (1/1000 mm) or 0.00254 inches. A
mesh size is the number of wires per inch in a screen mesh.
Thus a mesh or grit of 100 will pass through a screen with
100 wires to the inch (or 10,000 openings per square inch),
but can't pass through the next smaller screen.


Col 1 Col 2 Col 3 Column 4
----- ----- ----- --------
1/4 0-1/2 100,000 Superfine Polishing
1/2 0-1 50,000 "
1 0-2 14,000 Fine Polishing
3 1-5 8,000 "
6 4-8 3,000 Lapping & Sanding
9 6-12 2,000 "
15 8-22 1,200 " ,Rapid Sandng
30 30-40 600 " "
45 30-60 400 Coarse Lapping,Sand
60 40-80 325 Vry Coarse Lap,Grind

There are many places which sell synthetic and real diamond
grit. Two places (thanks to David Arens) are:

Diamond Pacific
2060 W Main St,
Barstow CA 92311
800-253-2954

Alpha Supply Inc
PO Box 2133
Bremerton WA 98310
800-257-4211

Reportedly, both companies have a catalog and list natural
and synthetic diamond powder in grits from 60 to 100,000.
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