An impact hammer mountable to the drum of a rotary crusher employs an attachment bolt having a tapered head which is wedged into a tapered socket in the impact hammer body. A "supernut" is used to secure the bolt to the rotary drum. The supernut is tightened against the rotary shear head until it is snug. Then, threaded locking posts, which pass through the periphery of the supernut, are tightened repeatedly, thereby applying a great deal of tension the bolt shank and effectively stretching it. Any shocks applied to the impact hammer will drive the tapered head of the bolt deeper into the socket of the hammer body block, resulting in the maintenance of a secure hammer-to-drum union. The hammer body also has tungsten carbide chips embedded in a hardfacing material that is applied to the wear surfaces of the hammer.

A rotary drum having a cutter extending outward from the outer diameter of the rotary drum. The rotary drum further includes a sleeve. The cutter is retained in a position relative to the drum by at least one block having a surface that wedges the cutter and/or interconnected member against the sleeve.