Joint ring, manufacturing method of joint ring, and manufacturing method of bending tube for endoscope

A joint ring of an endoscope, comprising:

• a joint ring body including a joint ring wall having an inner surface, an outer surface, a first end surface, and a second end surface;
• and
• a first wire guide attached to the inner surface of the joint ring wall,
• wherein the first wire guide includes a first wire guide body including a first wire guide wall having a third end surface and a fourth end surface,
• wherein, in a central axis direction of the joint ring body, at least a first portion of the first end surface and at least a first portion of the third end surface are at a first axial position and at least a first portion of the second end surface and at least a first portion of the fourth end surface are at a second axial position,
• wherein the first end surface includes a first recess extending in the central axis direction and having a concave surface, and
• wherein the concave surface includes the first portion of the first end surface at the first axial position.