Replacing the chuck on a Milwaukee power drill is a common task that can be performed by professionals and hobbyists alike. Subjected to repeated use, the torque (twisting force) created by drills causes their parts to wear. If a bit can no longer be properly secured in the chuck, or the chuck fits loosely on the spindle, the drill is no longer safe to operate. A replacement chuck must be installed. Replacing the chuck requires only a few common hand tools and can be performed quickly with minimal effort.
Unplug corded drills, or remove the battery pack from cordless models so the drill cannot be operated while replacing the chuck. Open chuck jaws fully, using the chuck key.
Remove the hex–head screw inside the chuck (located at the rear of the opening), using a long hex key. The screw has a left–handed thread, which means that it must be turned to the right (clockwise) to loosen it.
Insert the short end of either a 3/8–inch hex key (used with 3/8–inch chucks) or a ½–inch hex key (used with ½–inch chucks) into the chuck. Tighten the jaws using the chuck key.
Lay the chuck on its side on the edge of a workbench, keeping the body of the drill in a horizontal position. The chuck body that mounts to the spindle has a right–hand thread, so you must turn it to the left (counterclockwise) to remove it. Rotate the hex key so its long end points to the left, and is is halfway between vertical and touching the bench top (angled at 30 degrees).
Grasp the drill body tightly. Strike the hex key downward until the chuck loosens. If the chuck does not loosen after several strikes, spray it liberally with penetrating oil. Allow the oil to penetrate for several hours, and repeat the procedure again.
Remove the chuck fully by continuing to rotate it to the left (counterclockwise). Be sure to check the spindle for thread damage and rust. Wipe any residual penetrating oil from the spindle before installing a new chuck.
Open the new chuck's jaws fully. Check the new chuck's threads to ensure that they are free of burrs and are not damaged. Install the new chuck, rotating it to the right (clockwise) on the spindle until it bottoms out.
Install a new chuck screw, turning it to the left (counterclockwise—remember that it has a left–hand thread). After tightening the screw, either plug in the drill or reinstall the battery pack. Insert a drill bit, and, using a scrap piece of wood, operate it in both forward and reverse, making sure that both the drill and chuck function properly.