Well I still say you can taper and press fit. OR you can turn the shaft a make it smaller on the ends then use a tap and die to put threads on the shaft then inside the sprocket. Also if you use the same material for the shaft and sprocket, i.e. alum on alum or steel on steel. then you can just weld them together. We are using a press and taper but I have access to a nice machine shop with a precision CNC mill and lathe so that might not be easy for you. Also you could taper and use a shrink fit press for an even stronger fit. But welding will be the easiest if you have compatible materials. I hope this helps and I hope I understand the system right, if not e-mail me at
jonnywalk@hotmail.com and describe it better or scan a drawing and send that and i will try to help you the best I can.