... sets: 1.clay,quarrying,mining,construction button bit 2.button,thread,tapered bit 3.chisel,cross,button etc Oil drill bit ... customers to choose, like taper bit(taper button bit, taper chisel bit and taper cross bit), thread bit( R thread and T thread), retrac bit and dth ... bit( from 3" to 8" are available)I. Thread button ...