... , tunnel drilling and shallow engineering drilling. AQ,BQ,BQ3,NQ,HQPQ,PQ3Double tube impregnated diamond core bitΦ46,Φ56,Φ59 ... reaming shellΦ56,Φ59,Φ75,Φ91,Φ95 AQ,BQ,BQ3,NQ,HQPQ,PQ3Electroplated diamond core bit description: ModelRegular sizesSuited stratumInternational standardSingle ... shellΦ56,Φ59,Φ75,Φ91,Φ95 AQ,BQ,BQ3,NQ,HQPQ,PQ3 NQ/HQ Impregnated diamond core bit/Electroplated Diamond Core Drill ...