... in China ISO9001:2000,SGS certification. Electroplated diamond core drill bit for mine, coal mine drill bits. all ... kinds of drill bit. the size is following:1, Double tube drill ... ,Φ59,Φ60,Φ66,Φ75,Φ76,Φ91,Φ94,Φ1102,single tube drill:Φ36,Φ46,Φ59,Φ75,Φ91,Φ94 ... zone;sandstone;shale;2,middle-hard stone:Fine single limestone;Reinforced concrete;dolostone;Hard sandstone;other middle ...