The utility model discloses a machinery stop gear, including graduation piece, gyro wheel and resilient means, the surface profile of graduation piece and the movement track of the motion structure among the mechanical structure suit, and it has the recess that is used for blocking the gyro wheel to open in spacing department, and the non - motion that the graduation piece was installed in mechanical structure is structural, the motion that the gyro wheel was installed in mechanical structure is structural, and the motion structure is passed through the gyro wheel and is rolled on the graduation piece, rolls when getting into the recess of graduation piece when the gyro wheel, realizes the spacing of structure of moving, resilient means installs in the motion structurally, provides the pretightning force for the gyro wheel. This stop gear has that the mechanism is simple, easily operation, advantage such as reliable durable, but the wide application realizes the limit function that machinery used in various machineries.