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Arotary table is a precision work positioning device used in metalworking. It enables the operator to drill or cut work at exact intervals around a fixed (usuallyhorizontal orvertical) axis. Some rotary tables allow the use of index plates for indexing operations, and some can also be fitted with dividing plates that enable regular work positioning at divisions for which indexing plates are not available. A rotary fixture used in this fashion is more appropriately called adividing head (indexing head).
The table shown is a manually operated type. Powered tables under the control ofCNC machines are now available, and provide a fourth axis toCNC milling machines. Rotary tables are made with a solid base, which has provision for clamping onto another table or fixture. The actual table is a precision-machined disc to which the work piece is clamped (T slots are generally provided for this purpose). This disc can rotate freely, for indexing, or under the control of aworm (handwheel), with the worm wheel portion being made part of the actual table. High precision tables are driven by backlash compensatingduplex worms.
The ratio between worm and table is generally 40:1, 72:1 or 90:1 but may be any ratio that can be easily divided exactly into 360°. This is for ease of use whenindexing plates are available. A graduated dial and, often, avernier scale enable the operator to position the table, and thus the work affixed to it with great accuracy.
A through hole is usually machined into the table. Most commonly, this hole is machined to admit aMorse taper center or fixture.[1]
Rotary tables are most commonly mounted "flat", with the table rotating around a vertical axis, in the same plane as the cutter of a verticalmilling machine. An alternate setup is to mount the rotary table on its end (or mount it "flat" on a 90°angle plate), so that it rotates about a horizontal axis. In this configuration a tailstock can also be used, thus holding the workpiece "betweencenters."
With the table mounted on a secondary table, the workpiece is accurately centered on the rotary table's axis, which in turn is centered on the cutting tool's axis. All three axes are thuscoaxial. From this point, the secondary table can be offset in either the X or Y direction to set the cutter the desired distance from the workpiece's center. This allowsconcentric machining operations on the workpiece. Placing the workpiece eccentrically a set distance from the center permits more complex curves to be cut. As with other setups on a vertical mill, the milling operation can be either drilling a series of concentric, and possibly equidistant holes, or face or end milling either circular or semicircular shapes and contours.
A rotary table can be used:
Additionally, if converted tostepper motor operation, with a CNC milling machine and atailstock, a rotary table allows many parts to be made on a mill that otherwise would require alathe.
Rotary tables have many applications, including being used in the manufacture and inspection process of important elements inaerospace,automation and scientific industries. The use of rotary tables stretches as far as the film and animation industry, being used to obtain accuracy and precision in filming and photography.