Also known as positive-drive drill chucks, these chucks mount to the pin-drive tapered spindles on mud mixers and older drills. Their pin-drive design locks these chucks onto your tool, so they won’t slip on the spindle, no matter how often you start, stop, or reverse. They grip bits just as tightly—use the included key to tighten or loosen the jaws. These heavy duty chucks are larger and heavier than medium duty chucks, so they provide a more rigid hold under high torque. They’re made for tough jobs, like drilling through hard materials and mixing thick slurries. For a long life and improved accuracy, they have a one-piece sleeve, center-ground jaws, and hardened wear points.