Gear cutter size for clockmaking

[ctwo]

Afaik those cycloidal teeth are only used in some areas and in some watches and clocks. But I've yet to find out when they are being used what the actual design reason is behind why there chosen for that specific part. It's probably something well known, obvious and simple to any watch maker.

Bottom of page 11 begins the reasoning: https://our.oakland.edu/bitstream/handl ... 0clock.pdf

[pete]

That answers a lot Ctwo, thanks. And some really good and interesting information in that as well. Other than for very low tooth counts which the involute profile can't do, it appears an involute tooth form is superior to cycloidal in every way including a measurable reduction in friction.

[ctwo]

They were said to be stronger too, but how much stress is there in a watch gear train anyway?

[RSG]

Can you post a close picture of the gear looking straight to the profile?

Hi Ctwo, it appears as though i am incorrect! At first glance it looked like an involute gear but it is in fact a Cycloidal as you can see in the pic.



and thanks for the link on the differences between gears....

[pete]

Very true Ctwo. But that PDF certainly answered the question I've had for years about why you only see cycloidal tooth gears in some watches/clocks and in only one or two areas when there present. It's a design issue with low tooth counts on the pinion gear. Without that the reduced friction with involute gears would obviously have been used instead. If I remember the details correctly, involute gears can be cut with as low as 12 teeth, but below 18 teeth that involute curve becomes less and less correct as the tooth count goes down. And that may be why the cycloidal was chosen in Ron's picture above.

[Bill Shields]

I have to giggle at the fellows assumption that Involute gears should replace cycloidal gears in clock making even though may cause the clock to be larger in size..

assuming that the 'clock' does not have to fit on one's wrist...perhaps this is not a bad conclusion...

i also have to giggle at the concept of 3d printing gears....but if all you have is a hammer then the whole world looks like a nail.

[pete]

Maybe for a kids toy repair I'd go with those printed gears in plastic. But I couldn't agree more Bill. Like anything else 3D printers have there place. When I see lathe change gear sets on Ebay for the more common models of South Bend and Atlas lathes, thanks but no thanks.