Patent ID: 8485021

Claim:
A measuring head for an air micrometer, the measuring head 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 characterized by comprising: 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 the measuring head characterized in that one or a plurality of measurement air nozzles are formed in the measuring-head tip portion the measurement air nozzles configured to blow 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 measurement-head body portion, the measurement air is supplied to the measurement air nozzles respectively through the individual measurement air supply passages, the measurement air nozzles are a first measurement air nozzle and a second measurement air nozzle each of which is formed to extend in a radial direction of the measuring-head tip portion, and which have an angle of 180 degrees with respect to each other in a circumferential direction of the measuring-head tip portion, the measurement air supply passages are a first measurement air supply passage for supplying the measurement air to the first measurement air nozzle and a second measurement air supply passage for supplying the measurement air to the second measurement air nozzle, and the measurement air is supplied from a first measurement air supply passage and a second measurement air supply passage that are formed in a support portion of the main spindle, through a first measurement air supply passage and a second measurement air supply passage in a rotary joint mounted on the measuring-head body portion, to the first measurement air supply passage and the second measurement air supply passage in the measuring-head body portion, respectively, or the measurement air is supplied from a first measurement air supply passage and a second measurement air supply passage that are formed in a support portion of the main spindle, through a first measurement air supply passage and a second measurement air supply passage in a rotary joint mounted on the main spindle as well as a first measurement air supply passage and a second measurement air supply passage that are formed in the main spindle, to the first measurement air supply passage and the second measurement air supply passage in the measuring-head body portion, respectively.