In the 1960's and 70's when I worked as a scientific glassblower, we used
glass lathes all of the time to make 3 stage diffusion pumps etc. The two
most common brands were Litton (best) and Bethlehem (light weight and
cheaper). There were a few other brands available - one nice one made in
New Jersey and several from Germany.
The drive system was always variable speed accomplished by a variety of
methods. This is necessary as the speed can be used to control wall
thicknesses when sealing the tubing. The motor drove a splined shaft. The
head and tail stocks were connected to this shaft by a timing chain (slack
could be adjusted out by a snubber bar). There can be no slop (backlash) or
the seal would devitrify or even break on cooling.
The tailstock must move in order to make a seal. There was always a crank
on the tailstock to drive the movement and a gear rack under the bed. The
bed was covered by a heat protective stainless steel sheet which passed
through the bottom of the tailstock. For heat we used movable surface mix
rack burners on the lathe bed, hand torches, or a Carlisle CC mounted on a
movable stand. Fuel was high pressure natural gas, propane, and/or hydrogen
depending upon the job. Oxygen was always used.
Most of the items we made utilized borosilicate glass with a relatively low
coefficient of expansion. Sealed glass must always be annealed to remove
stresses caused by the heating. There is much more to glass working than
merely making the lathe. Larger tubing requires a glass saw for cutting. A
wet belt grinder comes in handy. HF is often used to clean fresh cut tubing
ends before sealing. Various graphite paddles and tapers will be needed.
Heat resistant gloves are a plus!
A large part of glass lathe expense is the various chucks for holding the
tubing. Some were even 6 jaw (2 separately operating 3 jaw chucks in one
chuck) for holding a tubing in position within another piece of tubing. We
used to shim everything with (dare I say it?) asbestos tape. The through
hole was at least 4" on most of the lathes I used.
A good glass lathe is not cheap and would have very limited use without all
of the required associated equipment.
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