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Grinding is a common finishing process used for the sealing surfaces in valve manufacturing. Grinding can achieve high dimensional accuracy, geometric shape precision, and surface roughness for the valve sealing surfaces, but it cannot improve the positional accuracy between the various surfaces of these sealing surfaces. The dimensional accuracy that can typically be achieved for the polished valve sealing surface is 0.001~0.003 mm ； The geometric shape accuracy (such as flatness) is 0.001mm ； The surface roughness is 0.1~0.008. The basic principles of seal surface grinding include five aspects: the grinding process, grinding motion, grinding speed, grinding pressure, and grinding allowance. 1 Grinding process: The grinding tool fits tightly against the surface of the seal ring, and the tool performs complex grinding movements along this fitted surface. An abrasive is placed between the surface of the grinding tool and the surface of the seal ring; as the grinding tool and the seal ring’s surface move relative to each other, some of the abrasive particles slide or roll between them, removing a very thin layer of metal from the surface of the seal ring. The protruding parts on the surface of the sealing ring are first worn away, and then the desired geometric shape is gradually achieved. Grinding is not only a mechanical processing process in which abrasives act on metal, but it also involves chemical effects. The oils in the abrasive can form an oxide film on the surface being processed, thereby accelerating the grinding process. 2 Grinding motion: When the grinding tool and the surface of the seal ring move relative to each other, the path of relative sliding of each point on the surface of the seal ring with respect to the grinding tool should be the same. Furthermore, the direction of relative motion should be changed continuously. The constant change in the direction of motion prevents each abrasive particle from repeating its path of movement on the surface of the seal ring, thus avoiding the formation of noticeable wear marks that could increase the roughness of that surface. Furthermore, the intermittent changes in the direction of movement prevent the abrasive from being distributed more evenly, thereby failing to remove the metal on the surface of the seal ring in a more uniform manner. Although the grinding motion is complex and its direction changes significantly, it always proceeds along the contact surface between the grinding tool and the surface of the seal ring. Whether it is manual grinding or mechanical grinding, the geometric accuracy of the surface of the sealing ring is primarily influenced by the geometric accuracy of the grinding tool and the grinding motion. 3 Grinding speed: The faster the speed of the grinding motion, the higher the grinding efficiency. The grinding speed is high; more abrasive particles pass over the workpiece surface per unit of time, resulting in more metal being removed. The grinding speed is usually 10~240 m/min. For workpieces that require high grinding precision, the grinding speed generally should not exceed 30 m/min. The grinding speed of the valve sealing surface is related to the material of the sealing surface; the grinding speed for copper and cast iron sealing surfaces is 10~45 m/min ； The sealing surfaces of hardened steel and cemented carbide are 25~80 m/min ； The sealing speed for austenitic stainless steel is 10~25 m/min. 4 Grinding pressure: The grinding efficiency increases as the grinding pressure rises, but it should not be too high; generally, it ranges from 0.01 to 0.4 MPa. When grinding the sealing surfaces of cast iron, copper, and austenitic stainless steel materials, the grinding pressure is 0.1~0.3 MPa ； The sealing surface of hardened steel and cemented carbide is 0.15~0.4MPa. A larger value is used for rough grinding, while a smaller value is used for fine grinding. 5 Grinding allowance: Since grinding is a finishing process, the amount of material removed is very small. The amount of grinding allowance depends on the machining accuracy and surface roughness of the previous process. On the condition of ensuring the removal of residues from the previous processing step and correcting geometric errors in the seal ring, the smaller the grinding allowance, the better. The sealing surface should generally be finish ground before grinding. The polished sealing surface can be further lapped directly, with a minimum lapping allowance of: 0.008~0.020 mm for the diameter ； The surface allowance is 0.006~0.015 mm. A smaller value is used for manual grinding or when the material hardness is high, while a larger value is used for mechanical grinding or when the material hardness is low. The sealing surface of the valve body is not suitable for grinding; precision turning can be used instead. The sealed surface after finish turning must be rough lapped before further finish lapping, with a flatness tolerance of 0.012~0.050 mm.