Patent ID: 8467989

Claim:
A clearance measuring method for measuring clearance between facing circular surfaces of a first member and a second member each having the circular surface, comprising: a step of bringing a pair of probes each having a round tip end slightly larger than the clearance into direct contact with the facing surfaces and measuring a center-to-center distance 2Y between the two tip ends, and a calculating step of calculating and measuring a clearance value d 1 on the basis of the center-to-center distance 2Y between the tip ends, wherein, in the calculating step, on the basis of a predetermined relationship between the center-to-center distance 2Y between the tip ends and the clearance value to be calculated and measured, a measured value of the center-to-center distance between the tip ends is converted to the clearance value d 1 as follows: when: radii r 1 and r 2 of the circular surfaces of the first member and the second member, respectively, and a radius e of the tip ends are predetermined; a represents a center-to-center distance between the second member and the tip end, b represents a center-to-center distance between the first member and the tip end, s represents a segment corresponding to a segment b between the center of the first member and the center of the tip end and extending in a direction of extension of a center-to-center segment c between the first member and the second member, and t represents a segment corresponding to a segment a between the center of the second member and the center of the tip end and extending in the direction of extension of the center-to-center segment c, then: a=r 2+ e and b=r 1+ e; from the Pythagorean theorem, there are obtained s 2 =b 2 −Y 2 and t 2 =a 2 −Y 2 ; since c=s+t, there is obtained: c =√{square root over (( b 2 −Y 2 ))}+√{square root over (( a 2 −Y 2 ))}; and since the clearance value d 1 is represented by d 1 =c−(r 1 +r 2 ), there is obtained: d 1=√{square root over (( b 2 −Y 2 ))}+√{square root over (( a 2 −Y 2 ))}−( r 1+ r 2).