Yep, they seem to have been used for situation
s (watchmaki
ng, not clock making) where it was easier to run a slitting saw around a circle, and then load the result into the topping/rounding tool to get the final tooth form. They mainly seem to use what are often called Carpano cutters (although there may have been more than one manufactu
rer of said cutters); these were fairly interesti
ng little widgets -- basically disks, with one little section being cut nearly loose, bent up out of the plane of the disk, hardened, and then fitted with a little screw.
The screw, when tightened, tries to force the "sprung" section back down into the plane of the disk. Thus, by adjusting the screw, you can finely control the width of your cut while still using just one basic cutter for each "module" (they used their own numbering scheme described here:
http://www.vintagewatchmarket.com/horological_cutters.html ).
I still only barely understan
d these things, but they're kinda nifty.
