| 摘要 |
According to the invention, a tightening key (1), for example one with ratchet, has a graduation (11) and the pivot of a magnetised needle (8), whilst a fixed magnetic pole (12) easily couplable to a structure close to the assembly fixes the position of the needle 8. As the graduation turns with the article to be tightened, it is possible to check the rotation of this article with respect to the needle (8). <IMAGE>
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