In fact most are made out of 1/8 inch brass and nickel plated to make the surface hard. I've only seen 1 #10 steel gear, and 2 #16 steel gears.

Brass is just fine to use and a lot easier to cut.

The big thing is to have the top face of the gear perfectly flat or the camera will wobble slightly when revolving and could cause problems. In the factory they would often add small paper shims to level the gear on the tripod head. Usually the problem is not the ring gear but the rollers having flat spots. They need to be perfect, and have a slight crown on them like an over inflated tire. When the wear down and get flat, they have to skid slightly when going around and then start wearing out even faster. Think of it like a car going in a tight circle, the outside wheels need to turn faster. If both sides of the car's wheels were fixed to the axles so they had to rotate at the same rate, one side or the other would have to skid. In a microscopic way this is what is happening to the roller on the turntable unless it is crowned.

Also, be sure to keep everything oiled, not soaking with oil as that will attract dirt, but oiled often and then wiped down. 3 in one oil is OK not anything heavier unless you are going to Death Valley in August. This applies to the gear shafts in the camera too. Use a very small brush to apply just one drop to each journal, run the camera then wipe. Do it often, but NEVER lube the gear teeth, Brass gears run dry, or you are asking for dirt to stick in the teeth and cause banding. I can go to great length to tell you how to clean up a cirkut gear train. I have a couple of good tricks to keep things clean too.

My #16 is a fan camera and I can run it without fans attached but it is noisy and not worth the risk of vibration damage. I cheated and put ball bearings in the guts. This was not for the fast speed, but to give me more power when I am using a really big fan like a ten second job or even bigger. I just make sure the wind isn't blowing or it will never run smooth. To prove the point, cup your hand around a running fan for shelter and it will noticeably speed up.