Product Description
The 140mm PDC combined drill bit drills a pilot hole and reams it to 140mm final diameter in a single pass, eliminating the two-stage drilling sequence required when a standard drill bit and a separate reamer are run sequentially. In underground coal mine exploration programs where drainage hole and gas extraction hole construction requires 100-400m per shift, eliminating the reaming trip reduces total time per hole by 30-40% — a direct impact on mine ventilation and gas management schedules.
The combined geometry requires more careful WOB management than single-function bits because the pilot and reamer sections have different cutting depths at any given WOB. Applying excessive WOB (above 15 kN) causes the pilot section to advance faster than the reaming cutters can engage, creating an oversized pilot hole with insufficient reamer contact — this reduces reaming efficiency and increases vibration. Matching WOB to the combined cutting requirement of both sections is the primary operational adjustment for this bit type. For information on standard PDC drag bits in this size range, see PDC drag bits for well and mining applications (http://www.zzsungood.com/PDC_Drag_Bit.html)
Primary applications: gas drainage hole construction in underground coal mines (140mm hole diameter accepts standard 100mm gas extraction tube installation with 20mm annular clearance for sealing grout), coal seam exploration holes where single-pass drilling from a surface rig or underground drill chamber requires finished-diameter holes without a reaming trip, and water injection holes for hydraulic fracturing programs in thick coal seams. This bit is most effective in formations up to 100 MPa — harder rock increases vibration from differential loading between pilot and reamer sections.
Recommended parameters: WOB 10-15 kN, RPM 100-200. Combined bits operate at lower RPM than single-function drag bits of the same diameter because the differential cutting depth between pilot and reamer sections creates a cyclical torque variation at each revolution — high RPM amplifies this variation into resonance that damages both the bit and the drill rod connections. Water flush at 30-50 L/min maintains cooling and cuttings transport for both the pilot and reaming sections simultaneously.
- Related product: 150mm Three Wings PDC Drag Bit For Well Drilling
Factory sales 140mm PDC Combination Bit PDC Reaming Bit for Mining
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