The DTH Hammer is a high-efficiency percussive drilling tool that delivers energy directly to the drill bit via a reciprocating piston driven by compressed air. It consists of components such as the top sub, air distributor, piston, control sleeve, and bit retainer. Widely used in hard rock formations, it provides superior penetration rates, borehole accuracy, and is ideal for blast holes, water wells, geothermal wells, and anchoring works.
A Down-the-Hole (DTH) Hammer is a percussion drilling tool placed directly behind the drill bit, driven by compressed air. It transmits high-impact energy directly to the bit for efficient rock fragmentation. DTH hammers are widely used in applications such as:
l Blast hole drilling in mining
l Water well drilling
l Geothermal well construction
l Foundation piling
l Slope anchoring and ground reinforcement
No. | Component |
Top Sub | Connects to the drill rod; transmits torque and compressed air into the hammer. |
Air Distributor / Check Valve | Controls the air flow to direct the piston motion. Includes a check valve to prevent backflow. |
Outer Cylinder / Housing | The main body of the hammer. It encloses all internal components and defines the hammer size. |
Piston | The core of the hammer. It reciprocates vertically under air pressure and strikes the drill bit. |
Control Sleeve / Guide Sleeve | Regulates piston movement and timing, determining frequency and impact energy. |
Bit Retainer / Driver Sub | Connects the hammer to the drill bit, transmitting impact and rotation. May include spline or key mechanisms. |
Drill Bit | Typically a button bit made of tungsten carbide, it directly breaks the rock via repeated impacts. |
Remark: Structural design may vary by manufacturer, but the above elements are fundamental to most DTH hammers.
Drill Rig → Drill Rod → DTH Hammer → DTH Bit
l High-pressure air is supplied from an air compressor.
l Air drives the piston to reciprocate inside the hammer.
l The piston strikes the bit directly, transmitting percussive force.
l The drill bit crushes the rock, while compressed air flushes the cuttings from the borehole through exhaust ports.
l Best for hard and medium-hard formations (e.g., granite, basalt, limestone).
l Requires an air compressor (typically 7–30 bar, ≥10 m³/min).
l Can drill vertically, horizontally, or at angles.
l Hole sizes typically range from 76 mm to 254 mm.
Advantage | Description |
High Penetration Rate | Impact energy is applied directly to the bit with minimal energy loss. |
Straight & Clean Boreholes | Accurate hole trajectory and smooth sidewalls, ideal for casing or grouting. |
Effective in Hard Rock | Excellent performance in tough, dense geological conditions. |
User-Friendly Operation | Simple configuration and reliable performance with low maintenance. |
l Ensure clean and dry compressed air to avoid rust, blockage, or internal wear.
l Lubricate the hammer using an inline oiler or manual injection to reduce component friction.
l Avoid dry firing (operating the hammer without the bit), which may damage the piston or retainer.
l Use compatible bits and hammers, ensuring matched splines and air channels.
l Replace wear parts like pistons, sleeves, and seals periodically for optimal performance.
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