I'm trying to use a gear system to run a rotating circuit board which will be attached to the larger of two gears.

I have a set smaller gear for the rotation which has 0.350" diameter gear with 15 teeth and Pitch Diameter of 0.312". Obviously I need to keep the teeth and gaps the same.

My gear which will have a circuit board seated onto it has an outer diameter of 2.7"

What I have been doing has resulted in the tooth thickness being too large, or the width of space being too large, resulting in gear slap or gear slippage. Suggestions?

  • 1
    $\begingroup$ What exaclty have you been doing? $\endgroup$
    – mart
    Mar 16, 2021 at 20:55
  • $\begingroup$ I've been sketching the teeth from the gear I am using to rotate the heatsink. I then have been putting that onto the heatsink and then doing a circular pattern. I'm wondering if there is mathematical way to do it since I can't find anything on Google. $\endgroup$ Mar 16, 2021 at 21:18
  • $\begingroup$ Any gear pair with the same diametral pitch (module for ROW) will have the same size teeth. You can scale up the diameter from that. $\endgroup$
    – jko
    Mar 17, 2021 at 12:34
  • $\begingroup$ If you have a set tooth size, then the circumference of the new gear is the old circumference times the new tooth count ratio to the old tooth count. Are you trying to create software to do this, or free-hand a drawing? A machinist can make a gear with any proper integer count of gears for a set diameter and doesn't need an accurate to scale drawing to do it. $\endgroup$
    – Tiger Guy
    Mar 19, 2021 at 17:42

1 Answer 1


One cannot increase the diameter of a gear without changing at least one other aspect of the gear design. If the original gear design has characteristics to which you object, it's important to correct the design, rather than make possibly-incorrect assumptions about a solution. In this case, your suggested solution of increasing the gear size without changing other appropriate features is likely impossible.

There are "mathematical" ways to generate gears that should solve your difficulty. I purchased at a reasonable cost Gear Template Generator program for the rare times I have to make a gear structure.

There are other programs which appear when searching for "gear generator" and also "free gear generator." If you are comfortable with Fusion 360 (free hobbyist version), there are a number of links for add-ons and various approaches to creating gears, although I've not researched them at length.

These generators produce involute gear shapes, which is how problems are avoided. You could also search for "how to make involute gears" which I have done. The resulting links provide clear design criteria for "drawing" your own gearing. This method involves using a draftsman's compass and other drawing tools. With today's computers, that's not the most practical method, but provides for better understanding.

gear generator software

Image from linked site.


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