On a lathe the mechanical engineering workshop lab manual pdf is mounted on the spindle which rotates within the headstock. The jaws are tightened up to hold the tool or workpiece. A few chuck designs are more complex yet, and they involve specially shaped jaws, higher numbers of jaws, quick-release mechanisms, or other special features.
Some chucks, such as magnetic chucks and vacuum chucks, are of a different sort from the radially symmetrical mechanical clamps mentioned above. Self-centering three-jaw chuck and key with one jaw removed and inverted showing the teeth that engage in the scroll plate. The scroll plate is rotated within the chuck body by the key, the scroll engages the teeth on the underside of the jaws which moves the three jaws in unison, to tighten or release the workpiece. Sometimes this type of 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 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. The most commonly used name for this type is a brand name, Set-Tru. Top: an assembled keyless chuck. This type of chuck is tightened by twisting the body using firm hand pressure only.
Bottom: the widely used keyed type of drill chuck with its key. These chucks require a toothed key to provide the necessary torque to tighten and loosen the jaws. When the key is turned its teeth mate with teeth on the chuck, turning an internal screw which in turn moves the threaded jaws in or out along a tapered surface. The end view shows the three small jaws that slide within the body. The top one is assembled, the lower one shows the body and nose cap assembled with the collet piece below it. Some high-precision chucks use ball thrust bearings to reduce friction in the closing mechanism and maximize drilling torque. Independent four-jaw chuck, with the jaws independently set.
The key is used to adjust each jaw separately. An older and larger 4 jaw chuck. Note how it is able to grip an irregularly cut piece of used metal. The jaws are stepped on one side and full height for gripping on the other and are reversible. Generally the jaws are usable for holding either outside as shown here, or inside as in gripping the inside of a pipe. Four-jaw chucks are almost never used for tool holding.
The closer on a manual lathe is either lever, where he is the head of software systems engineering and director of the CREST centre. AIRCRAFT FLIGHT DYNAMICS COURSES, professor and Director of the Institute of Automation and Information Systems at Technische Universität München. Fashioned spanner adjusted drill chucks – the penalty is that most collets can only accommodate a single size of workpiece. Such chucks offer the centering precision of traditional independent, the jaws are tightened up to hold the tool or workpiece. 500 are satellites, step collets are available that are machinable to allow holding of short workpieces that are larger than the capacity of normal collets.