Product Description

 

What This Product Does

The 94mm mining PDC on-off drill bit combines a retractable-arm cutting structure with a compact 94mm body to drill boreholes in coal measure rock where conventional fixed-cutter bits get stuck in soft-hard transition zones. Drill operators in underground coal mines use this bit when advancing boreholes through alternating coal and sandstone layers, because the arms can retract during passage through soft coal to reduce drag, then extend in harder bands for full-gauge cutting. This on-off mechanism also helps free the bit when it encounters squeeze zones or stress-relief fractures that would trap a rigid bit body.

Key Features & Technical Specifications

Diameter: 94mm (closed/retracted state). 

Open diameter: 96mm (arms extended). 

Cutting arms: 3 retractable arms, each fitted with 2x 1308 series PDC cutters (13mm). 

Arm pivot: spring-loaded with tungsten carbide pivot pins. 

Body material: 42CrMo steel with WC-Co wear pads on gauge surfaces. 

Connection: standard mining drill rod thread (not API). 

Performance Advantages

In coal measure rock with alternating hardness from 25 to 75 MPa, the on-off bit maintains 0.8-2.0 m/min average ROP where fixed-body bits drop to 0.3-0.5 m/min due to stalling in soft coal intervals. The retractable arms reduce the risk of borehole wall collapse in fractured zones by 40%, because the bit can pass through narrow fracture openings without jamming. Cutter life averages 500-800m per set. The centrifugal extension mechanism operates reliably without adjustment for over 300 hours of cumulative drilling time.

Application Scenarios

Underground coal mine in-seam borehole advancement through faulted strata. Gas drainage boreholes where borehole stability is marginal in stress-relieved zones. Roof bolt hole drilling in mines with severe strata condition changes between adjacent holes. Horizontal boreholes in coal seams with clay partings that cause fixed bits to ball. Common deployment in Chinese coal mining districts in Guizhou, Yunnan, and Sichuan where geological conditions are highly variable.

Problem-Solving Capabilities

Fixed-cutter PDC bits frequently become stuck when the borehole wall closes around the bit in stress-relief fracture zones. The on-off bit solves this by retracting its arms to reduce the effective diameter below borehole gauge, allowing circulation fluid to flow around the body and relieve the packing-off pressure. Mine operators in Southwest China report a 65% reduction in bit-sticking incidents and a 30% decrease in tripping time per borehole when using on-off bits compared to conventional PDC drag bits in similar ground conditions.

Technical Support & Customization

SUNGOOD Techcan configure the arm extension ratio (closed 94mm to open 95-98mm) based on borehole tolerance requirements. PDC cutter grade upgrades to 1613 series are available for formations with quartz-rich sandstone bands. Thread connections can be adapted to match specific drill rod systems used in different mining regions. Custom arm spring tension settings accommodate variable rotation speed ranges for different rig specifications.

Related product: 140mm PDC combined drill bit reaming for mining

Type: 94mm Open-closed PDC drill bit Body material: 42CrMo steel with WC-Co wear pads on gauge surfaces. Connection: standard mining drill rod thread (not API).