[rfeenstra]

Yes, it is a mystery.  The Scott drive is definitely larger, making it easier to machine out of one piece. Philco's is so small that I presume they felt they needed a hardened assembly, hence the ball bearing.  I machined the one for the Scott but I doubt I could do the one for the Philco!  I have a couple of these 38-116 (or maybe they are 37-116's) chassis.  I hate to break them up by robbing parts.  Perhaps you need a complete chassis!? 


Morzh - I would have just machined it out of one piece and then hardened it!