The drill chuck has a singular purpose--to securely hold the drill bit in place during drilling. This is accomplished by having three jaw-type devices that are tightened around the circular drill bit using a chuck key. As the key is turned, the top of the chuck moves upward, forcing the jaws to tighten around the drill bit. Three jaw points are used because this forms a circle in two dimensions. Once the chuck is tightened the drill bit is secure and ready for use.
The drill chuck was invented in 1902 by Arthur Irving Jacobs. He went on to found the Jacobs Chuck Manufacturing Co., which is still producing drill chucks more than a century later.
The original design for the drill chuck has been adapted to highly specialized equipment as well as the modern small cordless drills. The invention of the chuck was key to the manufacturing industry just as it was experiencing an explosion of growth.
In addition to the keyed chuck, many newer drills have a keyless chuck that allows the user to tighten the chuck with her hand rather than a key.
Drill chucks are made in a variety of sizes to fit different drills and to hold a wide variety of drill bites and other instruments.