This is for a large rc helicopter. The sprag is used on the main drive gear to drive the rotor head and allows the rotor to free wheel for autorotations when the motor is shut down. A common sprag size for this size model is 15mm ID, 23mm OD, 12mm tall. Typically the mainshaft is 12mm and a steel sleeve is used as the inner race of the sprag. The outer race of the sprag is also typically a sleeve, 23mm id, 27mm od, 12mm tall, and gets pressed or loctited into an aluminum hub that is bolted to main drive gear.

The complication I'm running into is deciding what to do about this inner and outer sleeve. I'm trying to source something premade that will work for these sleeves, but having a hard time.

This is the sprag I will be using:

http://www.rcbearings.com/products/fe422z-one-way-bearing.html

I found specs on another site that specify the requirements for the inner and outer race. Needs to have a surface finish of 2.5um and hardness of hrc60.

Hardened 52100 seems like a common choice for this type of thing, but don't think it's something I can do myself. I think I could hit the dimensional and surface requirements in annealed 52100, but I've read that the hardening process is specifically tricky with this material and requires a decent amount of material left for grinding after hardening. I've thought about building a tool post grinder setup since I need it for other things, but grinding of hard 52100 is also not so easy from what I've heard.

For the first prototype batch, I'll probably only need 5 sets of inner and outer race, not sure what the cost would be to have these custom made. I'm kind of new to this whole process. Up until now I've either made my own parts, or found existing ones to work. Wouldn't even know who to contact to make these type of parts.

Anyway, looking for advice on how to approach this. Maybe there are pre existing races that I just haven't found. Otherwise not sure if I should try doing part of this myself, maybe turn the annealed parts and send out for both hardening and grinding, or just outsource the whole thing.

Any advice is appreciated.