The collet on the Dremel tool is the equivalent of the chuck jaws on a standard drill. Bits and attachments fit into the collet, and a nut tightens the collet around the bit. Loosening a collet nut usually requires only turning the collet nut with your fingers. However, when using a single attachment or bit for a long period of time, you might find that it is difficult to remove the bit or attachment. This is because the torque, over time, tightens the collet nut through use. Loosening a Dremel collet that is tight requires the use of tools supplied with the Dremel.
Unplug the Dremel power cord if you own an electric Dremel. If you have a cordless Dremel, press the battery release tabs on the back of the Dremel and pull the battery out of the unit.
Press and hold the shaft lock button on top of the Dremel. The shaft lock button is the small button in front of the "On/Off" switch.
Place the Dremel collet wrench around the collet nut. The collet nut is the knurled sleeve surrounding the collet.
Turn the collet nut counterclockwise with the wrench. Once the collet nut is loose, the collet is loose for changing out bits.