JD25A 3inch Water Well DTH Drilling Hammer

In air-circulation drilling, if a formation is too hard for penetration by a drag bit, a DTH hammer is generally employed. This tool was developed for the mining and quarrying industry. The ‘business’ end – the button bit – is studded with hemispherical tungsten carbide ‘buttons,’ and with channels built in to allow the passage of compressed air. When the hammer is pressed against the ground, the bit is forced into a pneumatic hammer action (like a road drill) by compressed air fed down the drill pipes. Then, as the tool is rotated in the hole, the buttons act across the entire base of the borehole. Most hammers rotate at speeds of 20 to 30 revolutions per minute, and blows can be struck at rates of up to 4000 per minute. Debris is normally flushed (blown) out of the hole at the end of each drill pipe. DTH hammers are most effective in hard rock formations such as limestones or basalts; soft, fine-grained formations tend to clog the air ducts or jam the piston slides.

Nonetheless, DTH hammers are extremely cost-effective and hence very popular with commercial drillers。