Connector connecting bolt, connector and connector assembly

A connector connecting bolt (10) that is mountable in a first connector (40) and connectable to a mating second connector (60), comprising:

• a head (12) at or near a first axial end part (1AEP);
• a screw portion (13) at or near a second axial end part (2AEP);
• a flange (14) bulging radially out adjacent to the head (12) and being engageable with the second connector (60) when properly connected to prevent any further tightening of the bolt (10);
• at least one stepped recess (16) between the first axial end part (1AEP) and the screw portion (13), and being recessed radially inwardly a sufficient amount to be fractured when an excessive tightening torque is applied;
• at least one retaining groove (18) between the stepped recess (16) and the screw portion (13) in an axial direction (A) and recessed radially inward for receiving a retaining member (80) that contacts the first connector (40) before connection of the first and second connectors (40, 60) for preventing detachment of the bolt (10) from the first connector (40);
• and
• at least one seal groove (15) between the stepped recess (18) and the flange (14) in the axial direction (A) and recessed radially inward for receiving at least one seal (30) to be held in close contact with the first connector (40) in a fluid-tight manner at the time of proper connection.