A Chuck is a specialised type of clamp used to hold rotating tools or materials.

Collet

A collet is a sleeve with a cylindrical inside and a conical outside. The collet has kerf cuts along it's length to allow it to expand and contract. A threaded section at the rear of the collet is used to pull it into a matching conical socket. As the collet is pulled into the socket, the collet will contract - gripping the contents of the inner cylinder. Collets are most commonly found on Milling machines, Lathes and precision grinders

Drill

A drill chuck is a specialised three jaw chuck used to hold drill bits or related tools.

The image at right shows an assembled keyless chuck at the top. The tightening action of this chuck style is performed by twisting the body using firm hand pressure only.

The lower images show the traditional keyed style of drill chuck with its key. The arbor is shown separately to the right. These chucks require a key to provide the necessary torque to tighten and loosen the jaws. The rotary action of the key turns the outer body which acts on an internal screw, this in turn moves the threaded jaws in or out along a tapered surface. The taper allows the jaws to encompass various sizes of drill shanks. The end view shows the three small jaws that slide within the body.

Another style of drill chuck holds the drill bit by means of detents. These detents provide the drive transfer and the retaining action to the bit. The clamping movement is applied by light hand action but it is a positive one with little risk of the chuck locking up, if the load on the drill bit gets too great. Some masonry drills and drill bits use this method.

Special Drive System (SDS)

The SDS uses a cylindrical shank on the tool, with indents to be held by the chuck. A tool is inserted into the chuck by pressing in, and is locked in place until a separate lock release is used. SDS relies on a tool having the same shank diameter as the chuck - there are three standard sizes: SDS, SDS+ and SDS-MAX. Most used in high power hammer drills, SDS chucks are never used to hold work pieces.

Three jaw

A three jaw chuck is a rotating clamp which uses three interconnected dogs or 'jaws' to hold on a tool or work piece. Three jaw chucks are self-centring and are best suited to grip circular cross sections. Three jaw chucks can be found on lathes and indexing heads .

Four jaw

A four jaw chuck is similar to a three jaw chuck, but with four dogs, each of which can be moved independently. This makes them ideal for gripping non-circular cross sections, but difficult to centre precisely. Four jaw chucks are almost never used for tool holding. Four jaw chucks can be found on lathes and indexing heads.

Self-centring four jaw

A four jaw chuck with a mechanism for centring the work piece. Sometimes used to refer to chucks where the jaws are moved in interconnected pairs.

Magnetic

Used only for holding ferro-metallic work pieces, a Magnetic chuck consists of a accurately centred permanent magnet face.

See Also

Faceplate and driver