Hole Diameter

Common Core Drill Hole Diameter Codes

Code	Core Diameter [mm]	Description
BQ	36.5	Small-diameter core typically used for preliminary exploration or low-recovery ground; rarely used for mechanical testing.
BXM	41.7	Intermediate size between BQ and NQ; sometimes used to improve recovery in fractured zones while keeping tool size small.
NQ	47.6	Standard core size for exploration; commonly used in geotechnical mapping and strength testing.
HQ	63.5	Widely used diameter in geomechanics programs due to improved recovery and sample volume; suitable for UCS and triaxial tests.
PQ	85.0	Large-diameter core for high-recovery or structural logging; enables selection of high-quality specimens.