Workshop Hints
Wheel cutting hints
The British Horological Institute has compiled a digest of the following from e-mails sent to the Clock/Clockers mailing lists on the Internet. The information here does not necessarily indicate a method approved by the BHI, we are only publishing this digest so that others can decide for themselves whether the methods listed below will suit them.
The emails were from::
Gene Sizemore, John, Eliot Isaacs
Is it best to hold the blank on a vertical slide and the cutter in the lathe's headstock? Or is it better the other way round?
Generally, there is no concensus of opinion. Some lathe manufacturers provide equipment to cut wheels both ways.
As a general rule:-
- For steel pinions, where the power needed is relatively large, mount the pinion blank in a fixture on the vertical slide, so that you can use the full power of the lathe headstock.
- For brass wheels, where you need a fast cutter speed (particularly with fly cutters) mount the wheel in the lathe headstock and run the cutter from a high speed spindle on the vertical slide.
Stepping to each tooth
There are two ways of stepping around the wheel blank so that the teeth are equally spaced, either a dividing head or a division plate.
- A dividing head uses a worm and wheel to give very large number of possible wheel counts. There is a possibility of backlash once the dividing head starts to wear. With careful use this can be kept to a minimum.
- A plain division plate with the right number of holes is attached directly to the pinion blank or lathe mandrel. There is no possibility of backlash, no trouble in fancy calculations or losing count. A good rigid detent is also essential - this is one of the major factors in avoiding chatter and getting a good finish on the teeth. The main problem is that if you want a number of teeth not covered by the plate you have, you need to by another plate.
