... mass produce the motor powered and diesel powered portable screw air compressor, breaking the monopoly of foreign brand in ... from 32 to 60mm)II. Screw Joint rock drill head,screw connecting sleeve . 1.>R-screw drill ,screw connecting sleeve. ( R28,R32, ... R38 The diameter is form 38 to 102mm)2.>T-screw drill ,screw ...