air hammer drilling high pressure down the hole hammer wind pressure:0.5-2.5mpa Impact frequency : ... can manufacturer the best qualith DTH drill bit, DTH air hammer. Now we can supply 90mm-254mm(3.5"-10") ... DTH air hammer bit, 340,350,360,380, COP44, COP54, COP64, COP84 ... , 3"-8" DTH air hammer and 340,350,360,380 4",5",6",8" quick ...