Precision Tested and Certified to 0.0016" T.I.R Max at Half Capacity. Self-Tightening Feature Automatically Increases Gripping Force Proportional to Increased Torque to Prevent Tool Shank Slippage. All Components Exposed to Wear Are Completely Hardened to Maintain Accuracy and Extend Chuck Life. Jacobs® Taper Mount Permits Use on A Wide Range of High Accuracy Drill Presses, Jig Borers, Milling Machines and Production Drilling Equipment.