A rotary table includes a base body, a movable ring rotatably arranged on the base body, a fixed ring arranged on an inner periphery side of the movable ring and fixed to the base body, and a plurality of rolling elements. The rotary table includes a sensor fixed to the base body and a dog fixed to the movable ring. The movable ring has a scale extending at least at a portion of an outer peripheral side surface, and a groove-shaped recess formed to be recessed inward from an outer periphery of the movable ring at a position corresponding to the scale on the outer periphery. The dog has a leg portion fitted to the recess, and a detected portion protruding outward from the leg portion and detectable by the sensor. The leg portion is able to be fixed to the movable ring at any position in the recess.

A machining centre, with a first machining unit formed in a Z-axis direction of a coordinate system formed by three mutually perpendicular axis directions X, Y, Z, and equipped with a machining tool arranged in a machining zone, and a first tool slide movable in an X-axis and Y-axis direction, which can be equipped with a clamping device. The first tool slide has a drive spindle, and the clamping device is rotatable about a first axis of rotation. A second machining unit is operable independently of the first machining unit, and has a second tool slide movable independently of the first tool slide in the Z-axis direction, and a second workpiece positioning unit movable independently of the first workpiece positioning unit in the X-axis and Y-axis direction movable independently of the first tool slide in the Z-axis direction and a second workpiece positioning unit.

A machining centre, with a first machining unit formed in a Z-axis direction of a coordinate system formed by three mutually perpendicular axis directions X, Y, Z, and equipped with a machining tool arranged in a machining zone, and a first tool slide movable in an X-axis and Y-axis direction, which can be equipped with a clamping device. The first tool slide has a drive spindle, and the clamping device is rotatable about a first axis of rotation. A second machining unit is operable independently of the first machining unit, and has a second tool slide movable independently of the first tool slide in the Z-axis direction, and a second workpiece positioning unit movable independently of the first workpiece positioning unit in the X-axis and Y-axis direction movable independently of the first tool slide in the Z-axis direction and a second workpiece positioning unit.

A cam mechanism includes a base, a roller gear, and a camshaft. The roller gear and the camshaft are rotatably supported by the base. The roller gear has a turret and a plurality of cam followers mounted on the circumference of the turret. The camshaft has a shaft portion and a tapered rib having a first tapered rib and a second tapered rib. The first and second tapered ribs are each engaged with the cam followers. The first and second tapered ribs are configured to rotate relative to each other around a rotation axis of the shaft portion during adjustment of preload at which the first and second tapered ribs are pressed against the cam followers. After the adjustment of the preload, the second tapered rib is fixed to the shaft portion, and the first and second tapered ribs are prevented from rotating relatively.