Torque Limiting Screw

A torque limiting screw assembly, comprising:

• a screw and a cap surrounding the screw rotatably secured to the screw;
• the screw comprising:
• a screw head having a narrowed neck at the top and a base of enlarged diameter at the bottom, the top of the neck having a central well defining a deformable rim;
• a base of the screw head having a plurality of peripheral radial teeth with contiguous cams each having outward facing surfaces between each of the teeth;
• and
• a threaded shank extending downward from the base;
• the cap comprising:
• a body with a plurality of resilient torque-transmitting arms extending downwardly from the body, said resilient arms disposed such that inward facing surfaces of the arms engage the screw head cams;
• the arms having trailing edges engageable with radial walls of the screw head teeth in a first direction of rotation and not in a second opposite direction of rotation, wherein rotation of the cap in the second direction of rotation imparts a preselected torque to the screw by the gripping friction of the arms against the cams;
• and
• an axial through bore of the cap having an internal radial collar of decreased inside diameter;
• means for rotatably captivating the cap to the screw comprising the screw neck rim deformed to capture the cap internal collar between the neck rim and the screw head base.