So I know from college (and a bit of googling, not gonna lie) that the minimum amount of teeth on a gear is 17 due to undercut forming in traditional cutting manufacturing.

Does this rule still hold valid if the gear is laser cut and there is no (at least I see none) undercut on the gear?

I'm asking because fewer teeth mean less travel thus a cheaper cut, when cutting a lot of gears, and I can achieve my gear ratios with 11 or even 9 tooth gears.

I'm attaching a CAD image of an 11 tooth gear with (correct me if I'm wrong) no undercut:

enter image description here

  • $\begingroup$ Repaired a gear drive the other day with 7 teeth. So not sure about your 17... However, it was a male/female thing. $\endgroup$
    – Solar Mike
    Nov 28, 2022 at 20:05
  • $\begingroup$ Starter motor drives have 9 teeth.. engage with a flywheel ring gear. $\endgroup$
    – Solar Mike
    Nov 28, 2022 at 20:06
  • $\begingroup$ I saw a pinion once with 7 teeth. For use in model helicopters. $\endgroup$
    – DKNguyen
    Nov 28, 2022 at 23:33
  • $\begingroup$ Differentials in rear wheel drive cars "always" have fewer than 17 teeth on the pinion gear. '"Always" in those I have seen. $\endgroup$ Nov 29, 2022 at 15:15


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