ThisPDC Bits for Roof Bolting Drilling.have good diamond pieces drilling fast and long life used.

Must use in the coal mine anchor cable supports and protections sneaking in the hard rock layer.suitable for soft medium or medium hard stratumf＜12

specifications:25mm 27mm 28mm,30mm,32mm,36mm,42mm,

thread size:M14X1.5  M14X2  M16X2  M1/2X12