A shaft coupling assembly includes a shaft coupling element having a coupling wall defining a channel configured to receive a shaft end of a shaft. The channel includes a coupling interface configured to mate to a shaft interface defined by the shaft end. Each of the coupling interface and the shaft interface define a mating non-regular shape, which may be configured as one of an irregular polygon and a hybrid polygon including linear and non-linear sides. The shaft coupling element includes a fastener bore and a counterbore having an axial counterbore depth greater than an axial depth of the fastener bore. The shaft end inserted in the channel to an inserted depth greater than the fastener bore depth and less than the axial counterbore depth is displaceable into the counterbore such that the shaft end is not engaged with the coupling interface by the fastener bore receiving the fastener.