In this article, you'll learn how to use a chuck key:
A chuck key is needed to insert the bit in to the chuck of the key. This key should be attached to the electric cord. The key has a round knob with a lot of teeth all around it. The round knob of the key is inserted in to one of the three holes located on the chuck. The key needs to be rotated clockwise, to the right, to tighten the chuck. You may need to rotate the key 3 or 4 full revolutions before you start seeing the teeth of the chuck pull together. Once the bit is held in place by the teeth of the chuck, move the key to the other remaining holes in the chuck to apply even pressure to the bit.
To remove the bit, place the key in one of the holes on the chuck and rotate the key counterclockwise, to the left, to loosen.