The DTH drill bit is the final execution end that breaks rock and forms the borehole. Its technical core lies in efficiently transferring impact energy from the hammer and achieving rapid cuttings removal, directly determining drilling speed, cost, and hole quality. Modern drill bits integrate design elements from structure, materials, and fluid dynamics to convert the hammer's immense energy into effective rock-breaking work.
I. Core Structure: A Precision System for Energy Transfer and Cuttings Removal
The drill bit body is forged from high-strength alloy steel. Its core is the carbide button arrangement. The button rows typically employ a combination of staggered layout and reinforced center buttons, ensuring uniform breakage under impact loading. The bit shank features precision threads for seamless connection with the hammer, achieving energy transfer efficiency exceeding 95%. The exhaust channels (inner/face flushing holes) at the bottom and sides are optimized using computational fluid dynamics. They generate a high-velocity jet stream under high-pressure air
, rapidly flushing cuttings out of the hole and preventing bit "balling" caused by re-crushing.
II. Working Principle: The Dynamic Cycle of Impact, Shearing, and Cuttings Removal
Energy Transfer: The hammer piston strikes the bit shank at high speed (15-25 m/s). The shock wave travels through the bit body to the carbide buttons.
Rock Fragmentation: Under immense impact force, the carbide buttons penetrate the rock, generating Hertzian cracks. Simultaneously, the bit's rotation creates shear force, causing rock to spall off in chips, achieving combined impact-shear rock breakage.
Cuttings Clearance: Compressed air flows through the bit's internal passages and jets out from the face holes at high speed, creating a Venturi effect. This carries cuttings upward through the annulus between the drill rod and the hole wall, ensuring the bit always contacts fresh rock.
