Do not close down the chuck jaws without a drill bit inside. The jaws will ride up unevenly and grip the drill bit non-concentric. Unscrew the chuck knob, opening the chuck jaws just far enough to remove the drill bit from the chuck. Using the palm of your hand, lightly push down on the top of the jaws until they all bottom out in the chuck jaw retainer slots. The jaws will travel and secure the drill bit evenly now. The chuck is ready to use. It may be necessary to repeat these steps each time you sharpen a drill bit.