Summary

I have made this for a test of Parkinbot's gearcutting library.

Please print this only with XY-size compensation of your printer. You don't know what I mean? Please print the testcube first. If you'll get a cube with X and Y is 20mm and the hole is 10mm, then it's all right. If your testcube is >=20.1mm and the hole is <=9.9mm then don't continue. Look for the parameter of XY-size-compensation in your slicing software and adjust this (slic3r and repsnapper has). If you don't adjust this, this object doesn't fit. In this case, other people write in their thing: sandpaper this. (good luck at the gears). I will go back to the basics: look for precision of your machine. My machine is an opensource machine and it provides precision. Your machine is a commercial machine and it doesn't provide precision??? At this website, the people works very different: some include a big gap in the stl and I have a rattle-precision print. Some like to have 20mm when they write 20mm, and it will not fit sometimes. -> see screenshot of slic3r. I use version 1.2.9 on linux.

STL files: gears.scad is copied and adjusted a little. pins.scad is the well known idea, but rewritten in the most cases. Holder is not very important, it works without holder.

https://www.youtube.com/watch?v=vRwl8jhBfac

twin projects:
https://www.thingiverse.com/thing:1439718
https://www.thingiverse.com/thing:2944091