Locked connections between two threaded members

Apparatus for coupling a first tubular member to a second tubular member comprising:

• a first ring coupled to the first tubular member and having a first castellated annular surface with teeth extending in first direction and having a first projection extending in a second direction opposite the first direction, the first projection having a beveled surface;
• a first recess in the first tubular member configured to receive the first projection and having a fastener-receiving bore;
• a key configured to be disposed in the first recess, the key having a through-bore aligned with the fastener-receiving bore and having a beveled surface engaging the beveled surface of the first projection;
• a fastener disposed in the through-bore and the fastener-receiving bore;
• and
• a second castellated annular surface coupled to the second tubular member with teeth extending in the second direction and meshing with the teeth of the first castellated annual surface.

A method for coupling or decoupling two aligned tubular members, the method comprising:

• coupling a first ring to a first end portion of a first tubular member, the first ring disposed adjacent a shoulder of the first end portion and including a first castellated surface;
• inserting a second ring onto a second end portion of a second tubular member, the second ring disposed adjacent a shoulder of the second end portion and including a second castellated surface;
• threading the first and second end portions together;
• engaging the first castellated surface with the second castellated surface;
• and
• coupling the second ring to the second tubular member;
• and
• moving the second ring toward the shoulder of the second end portion by moving a key radially outward while slidingly engaging the key with a tab on the second ring.