Endoscope bending tube manufacturing method

An endoscope bending tube manufacturing method of manufacturing a bending tube of an endoscope, by connecting plural ring tubes forming the bending tube, the endoscope bending tube manufacturing method including:

• arranging one of two adjacent ring tubes on an outer side of an other one of the two adjacent ring tubes to match positions of a pair of through holes formed at one end of the one that is an outer ring tube, with positions of a pair of through holes formed at one end of the other one that is an inner ring tube;
• after inserting a connecting shaft through both a through hole of the outer ring tube and a through hole of the inner ring tube, performing processing of making an end portion of the connecting shaft increase in diameter by plastic working of pushing and stretching the end portion in a radial direction of the connecting shaft;
• fixing an outer peripheral surface of the connecting shaft to the through hole of the outer ring tube by bringing the outer peripheral surface into close contact with the through hole of the outer ring tube;
• and
• rotatably connecting the one of the two adjacent ring tubes to the other one of the two adjacent ring tubes.