Abstract: In a measuring jig for measuring an inner diameter of a valve hole portion formed coaxially with a guide hole, the measuring jig includes: an insertion shaft inserted into the guide hole; and a measuring instrument having a probe that is disposed around an axis of the insertion shaft and that is brought into contact with an inner wall of the valve hole portion. The inner diameter of the valve hole portion is measured by way of the probe by turning the measuring instrument about the axis, and the measuring instrument is disposed on the axis.

Abstract: In a measuring jig for measuring an inner diameter of a valve hole portion formed coaxially with a guide hole, the measuring jig includes: an insertion shaft inserted into the guide hole; and a measuring instrument having a probe that is disposed around an axis of the insertion shaft and that is brought into contact with an inner wall of the valve hole portion. The inner diameter of the valve hole portion is measured by way of the probe by turning the measuring instrument about the axis, and the measuring instrument is disposed on the axis.

Abstract: A method of marking a number on a work. The number is read out by a data read-out means, the read-out data is electrically transmitted and returned in a secure manner, and a predetermined number is securely marked. The structure is made such that the chassis number is read out again at a time of reading out the chassis number from a pass card P on which the chassis number is displayed by a bar code reader (data read-out means) R and that the read-out data is transmitted to a sequence device (an arithmetic control apparatus) S so as to judge whether good or no good. Further, the data transmitted to a marking system (a marking means) M from the sequence device S is returned to the sequence device S from the marking system M so as to judge whether good or no good. Then, in the case that the received data is no good, the marking operation is stopped.