The invention discloses a
measuring instrument for measuring the roundness of an inner ring and an outer ring of an automobile hub bearing, and particularly relates to the field of bearing roundness measurement, the
measuring instrument comprises a working table, a
rotating disc is arranged on the upper surface of the middle of the working table, an adsorption cavity is embedded in the surface of the middle of the working table, and air holes are formed in the surface of the
rotating disc; a driving gear is fixedly connected to the outer wall of the middle of the driving shaft, a blade fan shaft is arranged on one side of the inner wall of the adsorption cavity through a bearing, a blade fan gear is fixedly connected to the outer wall of the middle of the blade fan shaft, a
spiral blade fan is fixedly connected to the outer wall of the top of the blade fan shaft, and a measurement supporting
assembly is arranged on one side of the
rotating disc. An auxiliary adjusting
assembly is arranged on the side, away from the measurement supporting
assembly, of the rotating disc. According to the device, the
spiral blade fan can be automatically driven to rotate through the rotation of the rotating disc, so that the workpiece is adsorbed, no mechanical clamping trace exists, the hub bearing workpiece is fixed through the assistance of adsorption force, and the detection stability is improved.