... bearing typeFormation or layer soft ,medium soft ,hard,medium hard,very hard formationButton size (extra features)Button bit,saw ... call) .Recommended drilling parameters of tri-cone rock bits Rock formationBit typeBit sizeDrilling weightRotary speedmminchkN/mmr/minVery softSoft ... 1/2539-83360-40medium hardHard Dolomite, Limestone, Hard Sandy, Rock etc.595.2~174.63 3/4-6 ... 3 1/2" REG Pin for Hard Rock