... mining,geologic drilling 2.long useful life, high efficiency, wide using range coal mining bits/coal mining cutter teeth/tungsten carbide drill ... , 29, 30, 32, 36, 42 mm.Normal Thread Model: M16*2; M14*1.5, M12*1.75; M14*1.5; M12 ... ×1.5325622 M12×1.75 coal bits/coal mining bits/tungsten carbide drill bit