... symmetric drilling tools, eccentric drilling tools, standardized API system casings, bit shanks and casing tubes which are fit for hydraulic drilling ... quality and reliability of the products.Tapered Drill BitType --Chisel Bits / Cross Bits / Button Bits Diameter---28mm,30mm 32mm,34mm,36mm ... Thread Rod---R25,R28,R32,R38,T38,T45,T51. Integral Drill Rod---H19/H22, Diameter---20mm - 42mm. rock drill bits