Maximum Drill Chuck Capacity Inch 34 Minimum Drill Chuck Capacity Inch 364 Mount Type Taper Mount Mounting Size JT4 Bearing Type Ball Bearing GS Ball Bearing Chucks are especially designed for HEAVY DUTY drilling applications on production drilling machines, jig borers, milling machines, lathes and radials The ideal choice for those jobs that require close tolerance drilling The ball thrust bearing reduces friction in the chuck’s closing mechanism, so the operator can apply more gripping power on the twist drill shank High precision, premium tolerance