Patent ID: 6886264

Claim:
A reference fixture for a roundness measuring instrument for acquiring origin information of the roundness measuring instrument that includes a workpiece rotary mechanism rotatable with a workpiece being set thereon and the detector having a sensor for measuring a surface profile of the workpiece, and calibrating a detector thereof, the reference fixture comprising: a mount provided on a top face of the workpiece rotary mechanism; a calibration master provided on a top face of the mount for calibrating the sensitivity of the detector by the sensor of the detector; a reference ball disposed above the calibration master for providing the origin information of the roundness measuring instrument by the sensor of the detector; and a holder provided on the calibration master to hold the reference ball, wherein the holder is formed in a dimension capable of measuring the reference ball by the detector in Z-axis direction representing an axis line direction of the calibration master and in X-axis direction orthogonal to the axis line.