A lathe chuck is a special kind of clamp used on a lathe. These chucks hold objects that are cylindrical, radial, or irregularly shaped, gripped by what are called lathe chuck jaws. Used on wood lathes for woodworking or on machinists’ lathes for machining, chuck jaws hold steady the objects to be worked on. On some lathes, it is the chuck that does the rotating while a power tool is steadily applied to the object in its grip. The lathe chuck jaws are usually tightened into place on the object using a chuck key, a t-shaped wrench.
One type of lathe chuck is called a centering cylindrical stock chuck, having circles on its faceplate that can be used to center an object being machined. The lathe chuck jaws open wide to accept the object and center it, then the individual jaws are tightened snugly, yet carefully, so that there won’t be any movement whatsoever of the object once rotation begins. A dial indicator mounted on the lathe centers the object and measures to be certain that each of the individual jaws is bearing an equal grip on the object. Relatively large movements of the object eventually become only slight movements, as it is perfectly aligned and centered.
Another type of lathe chucks are specialty chucks. These lathe chucks come in two-jaws, six-jaws and eight-jaws configurations. The right choice of lathe chuck jaws for these depends on the type and heaviness of the objects to be handled, and on how important perfect centering and tightness of grip will be. For example, six-jaw self-centering lathe chuck jaws are used for thin-walled work pieces or for gripping finished edges of work pieces, and the large number of jaws enables less pressure per grip in order to protect a finish. Two-jaw chucks are available in a soft jaw aluminum configuration to work more like a stop to hold custom fixtures for tooling. Most chucks have one resident jaw as a master jaw, but the other lathe chuck jaws can be purchased or replaced separately at any time.
Three-jaw chucks have both inside and outside lathe chuck jaws with concave surfaces and are used for handling large diameter objects of circular or hexagonal shape. One type of three-jaw chuck is called a drill chuck, and it is for specialty self-centering to hold drill bits and other similar rotary tools. Another three-jaw chuck is the one colloquially called Super Chuck, which uses ball thrust bearings, has high torque and is used in high precision work. Three-jaws chucks can’t hold irregularly shaped pieces or any square shapes, yet the variety of types of three-jaw chucks for different purposes keeps them in high use.
Another high precision lathe chuck jaws configuration are the four-jaws chucks. These have time-consuming individually setting jaws, yet can turn in offset position as when turning cams. Four-jaws chucks can hold square, rectangular and nearly any irregularly shaped object for high-precision work. They also have more grip for handling round shapes or thin walled work pieces that need more numerous, gentler grips to spread the tension against the surface.