Optimal shaft-hub connections

In all power transmitting machines the shaft-hub connection has a large impact on the overall machine size, if the strength can be increased we can reduce the size. The connection between shaft and hub is a machine element with many possible designs available and described in standards. The connection can be either permanent or changeable, the goal is in all cases to have as high a strength for the connection as possible. Focus is in the present paper on the connections with easy assembly and disassembly, that is, on positive connections (geometrically locked). The designs specified in standards are traditionally made with straight lines and circular arches. Alternatively the involute spline can be used. For this case the cutting tool shape is made with straight lines and circular arches. Present standard designs are not made with minimum stress concentrations as the main objective, other features as for example, easy manufacturing has the primary importance. In the present paper we show how the involute spline design can be significantly improved in relation to strength maximization by reducing the maximum stress. The maximum stress can in many cases be reduced by more than 54 % relative to standard design.