... bit sets: 1.clay,quarrying,mining,construction button bit 2.button,thread,tapered bit 3.chisel,cross,button etc Oil drill bit ... button bit, taper chisel bit and taper cross bit), thread bit( R thread and T thread), retrac bit and dth bit( from 3" to ... cut high hardness is not drill layers, facilitate the grinding.2. Cross type and cruciform type rock drill bits : Applicable with ...