pic: 4143 offseason motor in wheel swerve

[Kevin Ainsworth]

We used MITCALC Internal Spur Gears software to generate a tooth profile. They had a free 30 day trial a while back. We generated one tooth profile and then patterned the tooth around the gear. The internal gear was wire EDM'd.
You could possibly have them waterjet or high-def lasered. I would recommend bolting on the gear to your part, not integrating it into the design. Stock Drive Products also sells internal spur gears but the 1/4" thick ones are brass and the stainless/aluminum ones are only 1/8" so you'ld have to stack them up to get enough tooth width.