I did a glass-working course in my
final undergraduate year (1981-1982); and in the research lab where I
did my final-year project there was a town-gas (mostly methane) and
oxygen burner used for fixing-up vacuum lines, etc.. So, for practice,
I took to raiding lab rubbish bins for broken Quickfit (ground-joint
borosilicate) glassware; and during the long boring periods of waiting
for spectroscopic scans to complete, I salvaged glassware parts and
welded them together to make usable items. These were mostly things
like separating funnels, still-heads and vacuum adapters. Hand
annealing was the only option, and so some of it cracked where I had
welded too close to cones, sockets and stopcocks; but a lot of it was
fine, and I still have some perfectly serviceable pieces.
More recently, I have
become interested in vacuum systems again; this time for the purpose of
using the ionisation of low-pressure gas to reveal the standing-wave
patterns on helical transmission lines. This work is self-funded
however, and I seem to have developed a powerful aversion to paying the
prices that science equipment suppliers ask for vacuum system
components. The solution, of course, is to revive the art of the glass
vacuum line, which is cheap and cheerful, and has the advantage that it
doesn't conduct electricity.
There is however more
to making a vacuum line than welding bits of glass tubing together. It
is a collection of components that includes traps, gauges, valves,
stopcocks, ports and receiving chambers. Thus a certain manufacturing
capability is required beyond the possession of an oxy-propane torch,
and this leads to the desire to own a glass lathe. Such machines are
rare, fabulously expensive, and much sought-after; but they are not
particularly complicated, and making one is not beyond the capabilities
of a small workshop equipped with a lathe and a milling machine.
of home-built glass lathes can be found on the web, but most designs
seem to be based on the metal-working lathe. This is not a good
approach. About the only thing that a glass lathe has in common with a
metal lathe is that the workpiece is rotated about a horizontal axis.
After that, there is no obvious similarity. A glass lathe is an
anti-gravity machine, allowing molten glass to be worked without
sagging. Its typical rate of rotation is about 1 revolution per second.
There is no need to apply any torque to the workpiece, which is held
lightly in a very-soft-jawed chuck. Large diameter tubes need to be
able to pass through the chuck, which means a large spindle throat.
Finally, the basic operation performed on the machine is that of
joining co-axial glass tubes. This requires two chucks rotating in
synchrony; one fixed horizontally (the headstock); and one moveable on
a sliding bed, or on rails (the tailstock).
>>>> More when I get time . . . .
Dual spindle glass lathe
Lindsay Wilson. Home built glass lathe + collected photographs of other
examples + useful links.
. Rail-based construction for
Tubecrafter. This design recognises the need for a large throat in both
lathe chuck using worm gears
- Dalibor Farny,
Nixie tube maker.
Making Nixie Tubes
- Dalibor Farny
Laboratory Glassworking for Scientists
A J B Robertson, D J Fabian, A J Crocker, J Dewing, Butterworth 1957.
Chapter 6 (p97-101) gives a description of the Edwards G3
. Figs. 34 and 35 from the book are
Making an ornamental vase
Valley Glass Works
2014). The glass billet, heated to
a viscous state, has been attached to the end of a thick-walled steel
The billet is initially rolled on a steel plate to form a
bulb. The bulb can be blown through the tube if a hollow item
required. The tube is then rolled backwards and forwards on a pair of
steel rails, to give a lathe action, occasionally reheating it in a gas
furnace to maintain viscosity, while the item is shaped using a
heat-proof pad and various steel tools. Once finished and
cut from the tube, the item is subjected to a slow annealing process
involving a series of progressively cooler ovens.