A Down-The-Hole Drill is called DTH in most drilling terms. The down-the-hole drill is basically a mini jack hammer that screws on the bottom of a drill string. The fast hammer action breaks hard rock into small flakes and dust and is blown clear by the air exhaust from the DTH hammer. The DTH hammer is one of the fastest ways to drill hard rock. Now smaller portable drillcat drilling rigs with DTH hammers can drill as fast as much larger truck rigs with this newer technology. In DTH drilling, the percussion mechanism – commonly called the hammer – is located directly behind the drill bit. The drill pipes transmit the necessary feed force and rotation to hammer and bit plus compressed air or fluids for the hammer and flushing of cuttings. The drill pipes are added to the drill string successively behind the hammer as the hole gets deeper. The piston strikes the impact surface of the bit directly, while the hammer casing gives straight and stable guidance of the drill bit. This means that the impact energy does not have to pass through any joints at all. The impact energy therefore is not lost in joints allowing for much deeper percussion drilling. This is a Great break through for smaller portable water well drilling rigs, that before were limited. The DTH on smaller rigs now can get same results as large heavy truck rigs. `