A new high energy impact hammer incorporating a fluid tappet and a high velocity piston is described which offers improved productivity, safety and reliability in rock excavation, structure demolition and secondary boulder breaking. Two models of this hammer are discussed, the 411 with a blow energy of 6000 ft. lb. (685 kg.m.) and the 514 with 20,000 ft. lb. (2275 kg.m.). The attachment of these new tools to a wide range of excavators and special machines is shown. The process of impact breaking is analyzed and several examples of effective use of these hammers are presented.