A self-centering chuck, also known as a scroll chuck, uses dogs (usually called jaws), interconnected via a scroll gear (scroll plate), to hold onto a tool or workpiece. Because they most often have three jaws, the term three-jaw chuck without other qualification is understood by machinists to mean a self-centering three-jaw chuck. The term universal chuck also refers to this type. These chucks are best suited to grip circular or hexagonal cross-sections when very fast, reasonably accurate (±0.005 inch [0.125 mm] TIR) centering is desired.

Sometimes this type of scroll chuck has 4 or 6 jaws instead of 3. More jaws grip the workpiece more securely if it is truly cylindrical, and thin-walled work will deform less. Four jaws are also useful for square bar work.

There are also independent-jaw (non-self-centering) chucks with three jaws.

There are hybrid self-centering chucks that have adjustment screws that can be used to further improve the concentricity after the workpiece has been gripped by the scroll jaws. This feature is meant to combine the speed and ease of the scroll plate’s self-centering with the run-out eliminating controllability of an independent-jaw chuck. The most commonly used name for this type is a brand name, Set-Tru. To avoid undue genericization of that brand name, suggestions for a generic name have included “exact-adjust”.

Three-jaw chucks are often used on lathes and indexing heads.

Di Chun Iron Work Co., Ltd. is the professional manufacturer of producing scroll chuck and kinds of power chucks. If you are interested in learning further specification and what do them look like, welcome to browse our website and feel free to contact with Di Chun.

Article Source: https://en.wikipedia.org/wiki/Chuck_(engineering)