A friction bush is an excellent way of coupling a timing pulley to a drive shaft. A friction bush is constructed with a pair of precision ground tapers. Tightening the locking screws drives the tapers over each other forcing the inner taper to compress on the shaft and the outer tapper to compress on the driven element. High torque can be transmitted in a compact coupling. This arrangement minimises stress raisers for better resistance against fatigue.
Of great benefit is the easy of machining and installation. The only machining required is to bore the driven element to the correct size and tolerance.

In many cases the bush can be completed recessed into the driven element. installation is also simple as the assembly can be aligned along the shaft and rotated prior to tightening the locking screws. In most cases the elements can be removed and reused as they come jacking screw holes to break the connection if the bush is still seized when the tightening screws are released.