A method of inserting a rivet into a workpiece comprises moving the rivet and workpiece relative to one another, along a longitudinal axis of the rivet, so as to drive the rivet into the workpiece. The rivet is rotated about its longitudinal axis, relative to the workpiece, for at least part of the time during which it is in contact with the workpiece. The speed of said rotation, or the speed of movement along the longitudinal axis of the rivet, is altered at least once before driving of the rivet into the workpiece is complete. One axial end of the rivet has a tip for piercing the workpiece, and the rivet has a substantially cylindrical shank extending longitudinally from the tip. The shank has one or more surface irregularities.