... of world top production technology, such as electro-hydraulic forging hammer, seal chamber furnace lines, precision machine tools and so on ... BIT---65MM to 254mm.2) DTH Hammer---76MM /90MM /110MM 3) Face ShapeConvex---Suitable for soft rock ( less than 1033.5bar)Concave ... .Thread Rod---R25,R28,R32,R38,T38,T45,T51. Integral Drill Rod---H19/H22, Diameter---20mm - 42mm. rock drill bits