Kennsen
29
On teeth and levers
Last post I claimed that gear wheels were just
advanced levers, and as with most things, its the details that make it
interesting.
Gear wheels have complex parameters that define the
shape of their teeth and standards have been established for their
manufacture. According to these standards engaging wheels should be of
the same “module” – the output of dividing pitch diameter by tooth
number. Various standards can then give a wheel’s tooth profile
depending on its module and number of teeth. The Swiss watch industry
has its own Normes or standards for gears. One I use is NIHS 2025. The
rather tattered page from below is from my own copy of the Normes book
and illustrates the calculations for the NIHS 2025.
Cheers Dave
(Kennsen Watches)
On teeth and levers
Last post I claimed that gear wheels were just advanced levers, and as with most things, its the details that make it interesting. Gear wheels have complex parameters that define the shape of their teeth and standards have been established for their manuf...
Thanks for highlighting the science
behind this seemingly simple but important component of a watch. I am no mechanical engineer but clearly we should all appreciate the work done here by early watch makers.
