Air-micrometer calibration device

An air-micrometer calibration device for calibrating a measuring head for an air micrometer, the measuring head being configured to be mounted on a main spindle of a machine tool at the time of measurement and inserted into a bush hole of a bush attached to a work table of the machine tool, for measuring an amount of eccentricity between the bush hole and the main spindle, the measuring head including:

• a measuring-head body portion;
• and
• a measuring-head tip portion provided on a distal end of the measuring-head body portion and configured to be inserted into the bush hole at the time of the measurement, in which:
• one or a plurality of measurement air nozzles are formed in the measuring-head tip portion, the measurement air nozzles configured to e measurement air to a gap between an outer peripheral surface of the measuring-head tip portion and an inner peripheral surface of the bush hole respectively through jetting openings in the outer peripheral surface at the time of measurement;
• individual measurement air supply passages corresponding to the respective measurement air nozzles are formed in the measuring-head body portion;
• and
• the measurement air is supplied to the measurement air nozzles respectively through the individual measurement air supply passages,
• the air-micrometer calibration device characterized by comprising:
• a small-diameter master hole;
• a large-diameter master hole;
• and
• positioning means for causing an axis of the measuring-head tip portion and an axis of the small-diameter master hole to coincide with each other when the measuring-head tip portion is inserted in the small-diameter master hole, and for causing the axis of the measuring-head tip portion and an axis of the large-diameter master hole to coincide with each other when the measuring-head tip portion is inserted in the large-diameter master hole,
• the positioning means includes:
• a pressure oil supply passage;
• a clamping sleeve;
• and a hydraulic pressure chamber surrounding a periphery of the clamping sleeve, and
• the clamping sleeve clamps the measuring-head body portion in association with a pressure of the pressure oil supplied from the pressure oil supply passage to the hydraulic pressure chamber, thereby causing the axis of the measuring-head tip portion and the axis of the small-diameter master hole to coincide with each other, or thereby causing the axis of the measuring-head tip portion and the axis of the large-diameter master hole to coincide with each other.