Tongue and Groove

In the above figure we have an assembly between a handle and a shaft. Because there is not enough room for two cap screws in order to fasten the two parts, a combination of a tongue-groove and one cap screw is used to fix them. The handle is made from square stock bar. One end of the handle is used as the tongue. It’s easy to machine a square groove at upper end of the rotating shaft (milling machine). A tight fit (transition) between the two parts must be provided in order to maintain a positive rotation (without jogs). For sure this not an elegant solution, but is an economic one.