Using the brass inserts, like TibTy mentioned, you can insert half into the sprocket and have into the flex wheel. This will make them spin together - even on a screw joint - and allow them to able to be powered by a chain connected to the sprocket.
Here is the link to the CAD I made to give you a visual of what I am referring to. The entire assembly is located on the first tab, and in the second, you can use the hide feature (right-click the part you want to hide) and see the inside of the model. I hope this helps!