coal bit 1.used in coal mining,geologic drilling 2.long useful ... range coal mining bits/coal mining cutter teeth/tungsten carbide drill bits/coal bitsProduct description:The coal bits are mainly used ... dry-type & wet-type.Dimension: 25, 27, 28, 29, 30, 32, 36, 42 mm.Normal Thread Model: M16*2; M14*1 ... M12×1.75 coal bits/coal mining bits/tungsten carbide drill bit