Magnetic tightening tool for preventing overtightening and undertightening

摘要

A tightening tool comprises a head having a socket for a nut to fit in, a head support supporting the head rotatably about the axis of the socket, and a handle integral with the head support. A magnet is attached to each of the head and the head support. The head and the head support are joined together by a force of attraction permitting these portions to rotate relative to each other upon the torque of tightening up the nut reaching a proper value. When the head support is rotated by turning the handle by hand, the head moves with the head support to tighten the nut. After the nut tightening torque has reached the proper value, the head support merely rotates idly with the head and the nut remaining unrotated even if the handle is turned.