Making a winding pinion

[Graziano]

Today making a winding pinion

[nickelsilver]

Wait are you T+T+T?

 

Good vid (as are most of theirs), but they missed something it seems almost everyone does when making a winding pinions- the feed of the angled cutter isn't in a line perpendicular to the axis of the pinion, it's a specific angle depending on the angle of the cutter and the number of teeth. This ensures full engagement of the teeth from periphery to center.

 

You can see it in this excellent illustration from Levins' Practical Benchwork for Horologists. They include a chart with the set angle for various numbers of teeth and cutter angles.

Sometimes the cutter angle isn't a nice round number 60/70/80 degrees etc., like this tiny Piaget 430P winding pinion. It's 67 degrees, which I've seen and done before and probably explains why I happened to have a 67 degree cutter in my collection. Plugging that and 8 teeth into the math (from Robert Porter's The Clock and Watch Makers Guide to Gear Making) gives a set angle of 10.14 degrees, or 79.86 depending how you view it, which falls neatly between the numbers in the Levin book. You can see how tilted the axis of the dividing spindle is in the milling setup- quite pronounced. Worked great, and a big thumbed-nose to Piaget for making the part so weak to begin with AND not selling parts!

Edited August 25, 2022 by nickelsilver