[philso]

You can also try drilling into the "hub" part of the sprocket and using a set screw. Once the sprocket is in place on the shaft, drill into the shaft, about 1-2 mm, through the hole for the setscrew to give the setscrew somewhere to "bite". It is also possible to use two setscrews for added security. Make sure the sprocket is clamped securely when drilling. This is probably best done on a drill press.