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What is a DTH hammer?

A down-the-hole drill rig, commonly referred to as a DTH by most professionals, is basically a jackhammer that screws onto the bottom of the drill string. The rapid hammering action breaks the hard rock into small chips and dust, which are expelled through the fluid (air, water or drilling mud). Down-the-hole hammers are one of the fastest methods of drilling hard rock. The system is thought to have been invented independently by Stenuick Frères of Belgium and Ingersoll Rand of the United States in the mid-1950s.

DTH is an abbreviation for "Dive into the Hole." Since the down-the-hole drilling method was originally developed for drilling down large diameter holes in surface drilling applications, its name comes from the fact that the impact mechanism follows the drill bit down into the hole. Later applications of the DTH method were found underground, where the drilling direction was usually upward rather than downward.

Down-the-hole drilling (DTH) essentially involves a drill hammer at the base of the drill string. It relies on three elements to drill: bit load (weight), rotation, and air. These active elements combine to effectively break up rock. As the drill string slowly rotates, the drill hammer is repeatedly pushed into the rock. The blowing force is provided by compressed air driving the piston inside the hammer.

A down-the-hole hammer is similar to a small rock drilling hammer. It screws onto the end of the drill string like a length of drill pipe. Like rock drills used above ground, it is aerodynamic and has a high circulation rate; unlike rock drill hammers used above ground, it combines rapid hammering and rotary drilling actions. This combined effect spins its chisel-like tip as it digs into rock, breaking it into fragments and dust. Because the down-the-hole hammer is pneumatically driven, it has an exhaust device that blows away chips and dust from the drilled hole.