Abstract: The precision machining of the threaded cartridge relief valve sleeve is a manufacturing process of grinding after carbonitriding. The shape and position error of inner cone will affect the service life and static and dynamic characteristics of the relief valve. This requires the need of manufacturing process to accurately control the error of the inner cone. Based on the process analysis, a manufacturing error model was established and applied to obtain a reasonable error range of the inner cone angle and to determine the relationship between the inner cone angle error and the grinding amount. According to the structural characteristics of the valve sleeve, a special detection device was designed and the detection principle and measurement error were analyzed to improve the detection accuracy through error proofreading. After heat treatment, the valve sleeve was divided into axial size groups and the unified principle of datum was adopted to ensure the stability of grinding accuracy. According to the detection principle and error model, the error calculation of the grinding test piece was carried out, and the grinding parameters were adjusted accordingly to make a qualified manufacturing error. In the subsequent manufacturing, the axial dimension of the detection sealing circle of the valve sleeve is quickly measured by the detection device, so that the manufacturing error falls within the control range, ensuring the controllability of the batch production. Based on the design and process parameters of a relief valve, results reveal that the control error of the inner cone’s own angle should be ±0.8°. The corresponding maximum grinding tolerance value of the axial direction of the sealing circle is 0.186 mm, while the corrected minimum grinding tolerance is 0.075 mm. Through experiments, the accuracy of the error model is verified. The angle measurement error of the detection method is 0.06°, while the measurement error of the axial dimension of the sealing circle is 2 μm. The deviation of the maximum grinding amount and the minimum grinding amount range caused by the angle measurement error is compensated by the shrinkage of the actual manufacturing error of the inner cone angle. The theory and method also provide a systematic process for manufacturing control and reverse engineering of the other inner cone.