ServoCity sells a great little 2:1 bevel gear ratio set: 2:1 Bevel Gear Set (1/4" Bore Pinion, 1/4" Bore Spur)

I have it currently set up in my project and was thinking a 1:1 gear ratio might be better suited for my purposes. All over the site it says the 13t gear must be paired with the 26t gear. Is there any reason why pairing two 13t gears together wouldn't work? I can't see why not, but, I want to confirm with people smarter than me.

  • $\begingroup$ two 13t gears would also mesh .... the angle between the two shafts would not be what you expect $\endgroup$
    – jsotola
    Feb 13, 2020 at 16:18

1 Answer 1


Bevel gears are not generally interchangeable. For a bevel gear set to work, the virtual cones generated by the pitch (or root) angles of each gear have to meet at the pitch apex. The image below shows the pitch apex.

Cross-section of bevel gears showing pitch apex

To help see the issue, I made the graphic below. I made a copy of the larger gear and tried to mate it to the smaller. Immediately, you can see that there are problems. The cones do not meet (blue arrow). We can also see that the gear teeth do not mesh correctly (orange arrow).

Cross-section of mismatched bevel gears

(The images above are not mine. I pulled them from the nice discussion on this site and modified: The Theory of Meccano Gears: Part 3 — Bevel Gears )


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