Ok, so assuming that I can find a nice alloy and that the key holds (would the key just shear in half if something went wrong?), a well-supported 3/8" shaft should not cause problems. How could we get the IFI sprocket to fit on a 1" shaft, though? The
hole in the middle is 1.125" and meant for a .5" bearing, and we don't have access to any machining facilities. I guess that we could use something like McMaster's 5905K68 on the inside of the sprockets, but we would still have to increase the diameter of the hole in the middle by 1/8" (and I'm not sure that would even be safe). Or we could use McMaster bearing 7929K21 on a 5/8 shaft - actually, that seems pretty feasible. Thanks for the advice!