Whether you intend to use your Bosch drill for drilling holes or driving screws, you will need to successfully open and close the chuck--the part of the drill that holds the bit in place--whenever you need a different size or type of bit, or to replace a broken or worn bit. Fortunately, this procedure is fairly straightforward, and should require no additional tools, other than the drill itself and the accessories that came with purchase of the drill.
Identify your drill chuck. Like many drill manufacturers, Bosch makes both keyed and keyless chucks. Look at the metal cylinder surrounding the tip of your drill. A keyed chuck will have regular star-shaped holes in this cylinder, while a keyless chuck will be smooth.
If you have a keyed chuck, locate your chuck key to open it. If you have a corded drill, check the cord--the key is often attached to the cord so it cannot be lost. It is a thin, pencil-shaped metal rod, about 3 inches long, with a star-shaped head that will fit into the holes on the chuck.
To open a closed keyed chuck, fit the chuck key into the holes on the cylinder near the tip of the drill, and rotate counter-clockwise. To tighten, rotate clockwise until "hand-tight;'--rotate until you encounter resistance, but don’t tighten as hard as you possibly can. Use all of the holes on the drill when loosening or tightening the chuck.
To open a keyless chuck, grip the cylinder around the tip of the drill and rotate it counter-clockwise by hand. To tighten, rotate clockwise until hand-tight.
When closing a chuck, observe the bit as the chuck closes. Small bits can become wedged in a chuck at an improper angle. Make sure the bit remains straight as the chuck closes around it.
Always exercise caution when operating power tools.