Diamond Core Drill Bits (BQ – PQ)
A diamond core drill bit cuts one annular ring and leaves the core intact. Which bit you need is decided by the rock, not by the rig: impregnated for hard abrasive formations, surface-set for broken ground and large diameters, PCD and carbide where core is not required. We supply BQ to PQ with matched reaming shells.
Four bit families, four different jobs
Most slow drilling is a bit-selection problem, not a rig problem. The matrix has to match the rock abrasivity, and the waterway has to match the flush.
Impregnated diamond bit
Diamonds are mixed through the whole matrix crown, and fresh diamonds are exposed as the crown wears. The default choice for hard, abrasive and broken rock from BQ to PQ. Matrix hardness (soft, medium, hard) is selected by rock type — a hard matrix in soft rock polishes and stops cutting.
Hard abrasive rock · 300 – 1,500 m programmes
Surface-set diamond bit
Larger, single-layer diamonds set on the face. Cuts faster in soft to medium rock and in large diameters where impregnated bits are expensive per metre, but is damaged quickly by broken ground and boulders.
Soft–medium rock · large diameter · shallow
PCD / PDC bit
Polycrystalline compact cutters on a steel body. Very fast in soft, uniform formations and in non-coring full-face drilling, but not intended for hard abrasive rock or for recovering core.
Soft–medium · full-face, no core
Tungsten carbide bit
Carbide inserts for overburden, clay, soft limestone and casing shoes. Cheap per metre, unsuitable for hard rock.
Overburden · casing shoes · soft rock
Core drill bit sizes: BQ, NQ, HQ and PQ
Hole and core diameters for the standard metric Q series. Bits, barrels, rods and reaming shells are supplied to the same size, so the whole string matches.
| Size | Hole diameter | Core diameter | Typical use |
|---|---|---|---|
| BQ | 60.0 mm | 36.5 mm | Small-diameter deep holes, portable and underground rigs |
| NQ | 75.7 mm | 47.6 mm | The most common exploration size worldwide |
| HQ | 96.0 mm | 63.5 mm | Larger core for geotech and higher recovery |
| PQ | 122.6 mm | 85.0 mm | Large-diameter core, wide-gauge ground, deep collars |
Imperial DCDMA sizes and thin-wall variants are available to order. Tell us the barrel you already run and we match the bit to it rather than the other way round.
Reaming shells
Same gauge as the bit, fitted behind it to hold hole diameter and protect the bit body.
Core lifters and cases
The spring that breaks and holds the core. Consumable, and the first thing to check when recovery drops.
Casing and shoes
AW to HW flush-joint casing with matching shoes for collapsing ground above the collar.
How the bit is chosen
Four questions decide it. Answer them and the matrix, profile and waterway follow.
Rock type and abrasivity
Granite, quartzite and abrasive sandstone wear a soft matrix fast; fractured and alternating ground breaks surface-set diamonds. This is the first and most important question.
Depth and rig torque
Deep holes need a freer-cutting bit: more torque goes into the string, less reaches the bit. If penetration drops with depth, the bit is usually too hard for the rig.
Waterway and flush
Face discharge for broken ground and high flush; standard waterways for competent rock. Wrong waterways burn the crown before the diamonds are used.
Core recovery requirement
Where recovery matters more than speed — geotech, resource definition — the bit, barrel and flush are chosen together, not separately.
What buyers ask about diamond bits
Keep reading
Tell us the rock and the barrel size
Rock type, depth, hole size and the bit you are replacing — that is enough for a bit, shell and lifter recommendation with a per-metre cost estimate.