Metrological apparatus

An attitude arm mounted to a support arm is rotatable about a pivot. The attitude arm holds a stylus gauge, which generates a signal representing deflection of the stylus in a measurement direction as the stylus follows a surface of a workpiece rotated on a turntable. An attitude switching mechanism allows switching between a first stylus attitude generally aligned with the turntable spindle axis and a second stylus attitude generally aligned perpendicular to the turntable spindle axis. To enable alignment of the measurement direction with the spindle axis, first and second adjusters enable the stylus tip to be moved perpendicular to the spindle axis and the measurement direction when in the first and second stylus attitudes, respectively. An orientation mechanism is provided to rotate the measurement direction of the stylus. A stylus tilt mechanism is provided to tilt the stylus about a tilt axis parallel with the measurement direction.