Down The Hole Drilling (DTH)
Applications: blasthole, water well, foundation, oil & gas, cooling systems and drilling for heat exchange pumps.
DTH is short for "down-the-hole". Since the DTH method was originally developed to drill large-diameter holes downwards in surface-drilling applications, its name originated from the fact that the percussion mechanism followed the bit down into the hole.
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 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 remains constant, regardless of the hole depth.
Pinnacle is a distributor of the following companies' DTH Hammers, Bits, and associated wear parts.
| Atlas Copco CMT | Bulroc (UK) | Halco America (Terex/Halco) |
Downhole drilling typically employs the following Bit Head styles and Button Styles
DTH Head Style
| Concave | Flat Face | Concave |
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| Suitable for most drilling applications, particularly hard, abrasive rock to give a combination of speed and good service life. | Used for general purpose drilling, the flat face design is considered effective in very broken ground as well as hard formations that tend to overdrill. | The concave bit design is an excellent all around bit, suitable for soft and hard formations. The cone shaped face design provides good stability during drilling, allowing for straighter holes while reducing equipment vibration. The carbide configuration design gives added penetration in many formations. |
| Ground Condition/Formation | Bit Head Style | Result |
| Medium to Hard | Concave | Excellent air flushing, less drill hole deviation, better penetration rates. |
| Very Hard | Flat Face | Suitable for fractured rocks. More aggressive drilling style. |
| Medium to Hard | Convex | Bit Faces comes in more contact with rock formation. Better hold penetration rates. |
