Brian Carling, G3XLQ / AF4K, A Former Crystal Maker!
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I used to work in a crystal factory and here is roughly how the
process worked there:
I worked for Cathodeon Crystals in Linton, Cambs. England around 1970
(Gosh that was 1970, a LONG time ago!) and stayed there for a few months helping
to make the precious rocks for the radio world!
I used to commute over 20 miles each way in a Morris series-Z "Half
hundred-weight van" with a 900 c.c. sidevalve engine, that hd a
maximum speed of 40 m.p.h. (no tickets) and had to use 40 weight
tractor oil in the engine due to leaking oil. The first thing that they showed me
was a very immpressive process for pumping air out of the hermetically sealed
crystal units, and these were all either HC-6/U size or the little
tiny ones that were in vogue in the 70s and 80s. What was cool was
that they made SOME HC-6/U size units with aGLASS case! Yes the
entire thing was made of clear glass. I don't know who was buying
those glass xtals or what they used them for. One could only guess.
We also were beginning to make some of the smaller HC-33/U size crystals.
The fabrication of crystals at Cathodeon Crystals ran something like
this:
Step 1 involved the reciving in of the raw crsytal which as I
remember was a man-made rock about 8-10 inches long, perhaps longer
and about 1-2" in section.
I think there was a step here that I was less familiar with in which
the large raw crystal was attached to a laterally reciprocating
machine that ground the top edge perfectly flat using a grinding
wheel with a mysterious white fluid tat ran over the wheel all of the
time to keep it cool. It took about 5 minutes at a time to run this
machine, and the operator sat on a chair watching it, and getting
hypnotized by the motion. They would often fall asleep and we had
great fun with these folks in the factory! One white haired elderly
gentleman with a red bow tie(!) from eastern Europe did this job and
he was known to take 40 winks in the afternoons, so we would
put a metal pan on the side of the moving table of the machine and it
wold eventually fall off making a terrible clatter and wake him up,
much to the delight of all of the factory workers nearby!
These raw crystals were then attached to a base plate in a computerized saw
after being x-rayed to get the ANGLE of the crystalline structure inside
the rock. They were then lined up on the base plate in the saw, a
carbide-edged rotary blade came down onto the rock and sliced it up
like sliced bread! The individual slices were then measured with a
micrometer to make sure that they were the right thickness that was
needed for the order. They were also x-rayed once again and the angle
to the nearest 1/100th of a degree was recorded on the paperwork that
travelled with the batch of crystals.
The next step was a lot of fun. They would take the crystal blanks
and put them in a device called a "lapping machine" - which had a
set of cog-like wheels that ran around inside two concentric circular
gears, the outer one rotating. These smaller cogs each had six holes
in them that could hold the crystals. The cogs came in many different
thicknesses depending on the desired final thickness and the
beginning thickness of the blanks. Once the crystals were in place,
they would be run FIRST in a slurry of thick grease that contained an
abrasive component. The operators had charts for how many minutes to
run them for a desired shift in thickness. The COARSE adjustment was
made first, and you could soon make a large difference in those
jewels! Operators were given a target thickness. Typically about 60
blanks would be whirring around in the lapping machine at any given
time of the day. They had a number of these machines and they ran all
day long. The final step in the lapping process was a set of
specialized lapping machines that were connected to the ANTENNA
TERMINALS of some EDDYSTONE receivers! As they turned inside the
machine, the grinding process would set up enough vibration of the
crystals that it generated NOISE In the receivers and you could HEAR
the crystals as the frequency shifted. Of course they would not ALL
be at the exact same frequency so you got a kind of wideband noise!
At several steps along the way, things could go wrong! The lapping
machines would sometimes go "UP!" That means it would all fly apart
and you had a mess of crstals and nasty grease everywhere and had to
pick your way through it all and start over.
Another problem was with "outliers" - some of the crystal blanks
would wind up being too far off from their target thickness at the
early stages or too far off frequency near the end. Often these ones
had to be tossed out. Anyone here live near a crystal factory?? he he!!
After that the FINAL fine tuning was done by spraying GOLD onto the
crystals, and that is how this plant did their electrode attachment.
They put gold on the corner of each side of the blank for an
electrical connection, and if they needed to lower the frequency a
tad, they just added a little bit more gold. Then the wirs were
soldered on, the whole thing was mounted in a holder & hermetically
sealed with the vacuum pump machine and out they went!
I only worked there a few months but it was most interesting!
Brian Carling
bry@mnsinc.com
http://www.mnsinc.com/bry/
(
geocities.com/capecanaveral/hall/8701) (
geocities.com/capecanaveral/hall) (
geocities.com/capecanaveral)