Gear Making Information

[Jim Meyer]

The HOT team has successfully cut steel gears on a mill. It was the year before I joined the team so I don't know all of the details.

In '99 they didn't have the SPI budget to buy the gears for their custom drive train so they made them. They made 20 pitch, 20 degree pressure angle gears in a variety of diameters. They were made on a CNC bridgeport with an index head. I'm not sure whether an index head is the same as a divider head.

They started with the proper diameter cold rolled steel round stock from SPI and a full set of gear cutters (you need different cutters for different sized gears). The gear cutters they used are like fly cutters except with involute profile shaped teeth. They cut several gearwiths at a time and then parted the desired facewidths off in a lathe. The cut gears were nearly indistinguishible from purchased ones. Even though the gears were not heat treated, there were no problems with durability. (They appeared to be oversized for the task though.)

If you have more questioins, I can get better information from the machinist who made them. Just send me an e-mail at James.L.Meyer@gm.com or post here.

It is my impression that with today's small parts budget you are better off buying SPI gears than trying to machine them this way.

Another solution to the Bosh motor gear problem is to press your own gear on the motor shaft. (Something the HOT team also did in '99)

Hope this helps,

Jim Meyer