Making a skeleton clock was a major task for me and wanted to minimise the time taken
on the project. Included in this was not to spend time on workshop equipment that
would likely only be used just the once.
When cutting clock pinions, the most common setup, if I am correct, is to support
the outer end with a form of tailstock, this would take some time to make so rejected
the idea. Another method I had seen was to place a support behind the pinion to help
take the machining force. Again I did not go with the idea as the support would need
resetting as the already cut teeth reached the rear of the pinion blank.
I did though realise that if the steady was curved to match the pinions diameter,
resetting would not be necessary, from that the idea shown in Photo 1 surfaced. A
few minutes to drill a close fitting hole in a scrap of steel and I was in business.
I didn't even have to cut the slot in the side of the support as this was cut when
cutting the first tooth space. Photo 2 shows the complete setup and using my basic
For the clock maker who would like to make a largish number of pinions to hold in
stock then a second support, perhaps a third or more, spaced off the angle plate,
would enable longer lengths to be machined.
Having cut the teeth on a single blank, sufficient for 6 pinions, I was left with
the task of dividing it to make single pinions, drilling them for the arbors and
turning the ends on some to be a close fit in the holes in the wheels in which they
were to fit.
The first task was to divide the blank into portions long enough for the pinions
to be made. Obviously, the first choice for holding them when parting off was to
use a collet. However, whilst I make a lot of use of ER collets on my lathe I find
that when closing them down to a size much smaller than their maximum the closing
force increases and it is a little difficult to determine when a proper grip is achieved.
I was therefore reluctant, perhaps unnecessarily, to hold the blank on its teeth,
as too high a grip, or too little and they slip, may result in damaged teeth and
a start again situation. Obviously not what I would like.As the projection from the
collet would not be that great I decided to hold it on the unmachined portion and
with a narrow parting off tool very very carefully part off the blanks.
I was now faced with very short lengths needing their ends faced, drilled for the
arbor's diameter, and in some cases, turned with a spigot to enter closely into a
hole in its mating wheel. The idea of gripping such short pinions using a collet
did not appeal, even less than the longer blank if parting off. I decided therefore
that using the lathes three jaw fitted with soft jaws would be a much better method.
Being soft, the jaws would deform very slightly around the teeth ensuring a secure
hold with much less force. Also, having machined the jaws whilst on the lathe, Photo
3, concentricity would be assured.
Even with only a length of around 5mm to grip in most cases, the method worked
well and I was very pleased with the result. Photo 4 shows a pinion being drilled
for its arbor.
I worked without soft jaws for very many years and now realise just how big a mistake
this was as so many tasks that would have bordered on the impossible are now carried
out with ease. Even if you are not into clock making, I cannot stress more highly
that soft jaws should be a standard item in the vast majority of workshops. If you
are new to using soft jaws then you may like to view my pages on their use..