ABSTRACT
The down-the-hole (DTH) hammer is designed to provide what is termed a 'blow mode', which comes into operation when the bit is in the extended position ahead of the hammer. The DTH hammer will produce a blow count or strike rate i.e., the number of times the piston strikes the bit in the order of 1400-3000 blows per minute depending on the design and the air supply available. An important factor to be considered in the engineering design of a DTH hammer is the energy transfer between the piston and the strike face of the bit. In the case of the cylindrical form the DTH bit is termed a button bit and the physical composition and characteristics of the buttons can be regulated to provide specific design features. Within any drill bit design there are certain features which can be varied either in whole or in part to tune the performance of a drill bit to meet specific conditions.
