Take any crankshaft with the taper you need to mount flywheel (in lathe) and use a hacksaw and cut it off and use the stub shaft you have now to mount the shaft and the flywheel in lathe. Use a cut-off tool and cut the outsidepart of the flywheel off ...cutting from face. Then turn down the edge or outside dia of the hub you are making too the size you want. I got a collection of stub shafts with various tapers...just to place flywheels on too turn down to make a hub. Capt,n