DTH (Down the hole) drilling is a rotary percussive drilling method. Hammer which is used for generating strong impacts is attached to the bottom of the drill string and a drill bit is attached to the lower end of the DTH hammer. The movement of the piston in the DTH hammer is caused by high pressure compressed air. The shock waves that travel to the bit are passed on to the rock mass through the cutting edges or carbide buttons on the bit. As a result, cracks are formed in the rock mass which results in formation of rock chips. Cuttings are removed from the hole by the air circulated from bottom to top to flush the hole.

RC (Reverse circulation) hammer bits are similar to conventional DTH bits. Deep channels on the outside of the drill bit head allow the exhaust air to force the cutting into the recovery ports in the bit face. Cutting are then air lifted by the discharged air up to the surface through the inner chamber of the dual-wall pipe.

Please contact us for any additional details and assistance in selecting the right bit designed for your particular rock drilling application.

Bitroc offers a comprehensive range of quality DTH and RC drilling bits for use in the mining, construction, and exploration industries in all kind of rock types and drilling conditions. DTH Bits are available in sizes from 3" to 18", with all type of shanks (Including Atlas Copco, Sandvik, Ingersoll Rand shanks etc.).

DTH bits come in three different standard bit head/face designs (Convex, Flat, and Concave), and with a variety of tungsten carbide button shapes to suit a wide variety of drilling conditions. Additional specific bit face designs, shanks and custom options are available on request.

Bit Selection

Bit life and penetration rate are the most important criteria in selecting the right bit for a particular application.

Face Selection

Convex Face bits are suitable for most drilling applications, particularly hard, abrasive rock to give a combination of speed and good service life. This face style gives good hole penetration and works well when drilling in broken and falling ground.

Concave Face design is an excellent all around bit, suitable for soft and hard formations. These face features will help drill straighter holes while reducing equipment vibration in medium to hard formations. This face has excellent air flushing characteristics.

Flat Face bits are general purpose bit, which will work in all rock conditions and are suited best for hard rocks and have a balance between penetration rate and hole deviation.

There are also different special design bit faces, which can improve the bit performance for specific drill jobs and ground conditions.

Carbide Selection

Round profile is the most common shape used in DTH Bits and is the strongest and most resistant to breakage. The domed shape provides reasonable penetration rate in medium rock, hard rock, and hard rock broken formations, in all types of drilling.

Ballistic profiles drill faster and have a more efficient rock breakage than rounded profile if used in soft and medium rocks. But ballistic button is prone to breakage if used in the wrong formations.

Semi-Ballistic profiles have a balance between round and ballistic shapes and characteristics, making them a choice in medium rocks for better penetration rate and longer carbide life.

Shank Selection

Type	Min Hole Size(mm)	Splines Qty.	Shank Length(mm)
Bit shank for 3” Hammer Series
DHD3.5	85	8	181
Bit shank for 4” Hammer Series
DHD340	105	8	210
SD4	105	8	260
Bit shank for 5” Hammer Series
DHD350	130	8	260
SD5	130	8	260
QL50	130	12	240
Bit shank for 6” Hammer Series
DHD360	149	8	308
SD6	149	8	324
QL60	149	12	253
Bit shank for 8” Hammer Series
DHD380	200	10	350
SD8	200	8	322
QL80	200	16	332
Bit shank for 12” Hammer Series
SD12	302	8	470
QL120	302	16	492

Other bit shank types are available on request.