| CPC G01B 5/12 (2013.01) [B25J 13/081 (2013.01)] | 13 Claims |

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1. An inside-diameter measuring unit comprising:
an inside-diameter measuring part including a contact point configured to move forward and backward in a direction perpendicular to a cylinder axis of a cylinder case part, the inside-diameter measuring part configured to bring the contact point into contact with an inner wall of a hole to be measured to measure an inside diameter of the hole while the inside-diameter measuring part is inserted in the hole;
a support frame part configured to support the inside-diameter measuring part; and
a floating joint part interposed between the support frame part and the inside-diameter measuring part to allow relative translation and rotation of the inside-diameter measuring part with respect to the support frame part, wherein
the floating joint part includes:
a rotation-allowing mechanism part configured to allow the rotation of the inside-diameter measuring part with respect to the support frame part; and
a translation-allowing mechanism part configured to allow translational displacement of the inside-diameter measuring part with respect to the support frame part
the rotation-allowing mechanism part includes a flexible body configured to allow deformation in a direction in which the inside-diameter measuring part is inclined
the translation-allowing mechanism part includes a translation body configured to allow translation of the inside-diameter measuring part in a direction intersecting the cylinder axis of the cylinder case part
the flexible body has one end coupled to the inside-diameter measuring part
the flexible body has the other end coupled to the translation body, and
the translation body is supported in such a manner as to be translatable with respect to the support frame part.
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