diamond core bits, diamond drill bits, diamond core drill: over 20years experience all kinds of size small order are workable diamond core bits, diamond drill bits, diamond core drill description: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:Φ28,Φ36,Φ46,Φ59,Φ60,Φ66,Φ75,Φ76,Φ91 ...