Diamond Bit

NMLC bottom-discharge impregnated diamond core bit

The NMLC bottom-discharge impregnated diamond core bit and reaming shell are designed for wireline coring systems, with standard outer diameter 75.3 mm and inner diameter 52.0 mm . The bottom-discharge waterway configuration directs flushing fluid to the bit face rather than across the core, reducing core erosion and washout in soft to medium-hard formations.

Technical Features

Bottom-Discharge Waterways : Flushing fluid exits through ports at the bit crown, cooling the cutting face and flushing cuttings without directly impinging on the core barrel interior. This is particularly effective with triple-tube core barrels, where core preservation is critical .

Impregnated Matrix Self-Sharpening : Diamonds are dispersed throughout a metal matrix. As the matrix wears, dulled diamonds are shed and fresh cutting edges are exposed. This provides consistent penetration rates and extended bit life in soft to medium-hard formations with moderate abrasiveness .

Optimized for Soft to Medium-Hard Rock : Matrix hardness and diamond concentration are balanced for formations such as shale, sandstone, limestone, and marble, avoiding the “polishing” or bit-slipping that can occur when a matrix is too hard for the rock being drilled.

Matched Reaming Shell : The reaming shell is sized 0.3–0.5 mm larger than the bit OD to maintain hole gauge and stabilize the drill string in soft formations .

Applications

  • Geological Exploration : Continuous coring in sedimentary and metamorphic terrains, with improved recovery in soft-to-medium interbedded sequences.

  • Engineering Investigation : Core recovery for dam, bridge, and tunnel site characterization, particularly where bottom-discharge flushing helps preserve fragile core in shear zones.

  • Mining : Resource definition drilling in coal measure rocks and metal mine host sequences of low to moderate hardness.

Recommended Startup Procedure

For a new bit, run at one-third normal weight-on-bit and approximately 100 rpm for the first 10 minutes to establish conformity between the crown and hole bottom before advancing to full drilling parameters . Reduce weight-on-bit in soft formations to prevent matrix embedding and waterway blockage; increase moderately in competent, medium-hard rock to sustain penetration.