Hey guys and greeting from team 1660, my team and I are fairly new to building gearboxes from ground up. What we want to know is what gear pitch to use.
Also if anyone else has any other tips on this process please reply also.
Will the gearbox be used for the drivetrain? If so, and if the motors and robots are anything like years past, 20 pitch seems to be the norm, and 3/8" face width is acceptable as long as you can keep your tolerances. 
On the first stage reduction on the small CIMs, you can go with 32 pitch if you want. Make sure they are all steel except in one very special circumstance 
Also, a lot of gears come with big heavy hubs. In most cases, don’t be afraid to reduce their width and or diamteter, or even eliminatate them altogether.
Yes it will be used for a gearbox. Its going to be a direct drive sort of system.