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A benchmark, as a core concept in mechanical design and manufacturing, serves as an important basis for determining the geometric relationships, position, and shape of parts or components. It is not only related to processing accuracy and assembly quality, but also has a direct impact on the performance and reliability of the entire mechanical system. In mechanical design, references are mainly divided into two categories: design references and manufacturing references. These two types of benchmarks play irreplaceable roles in the processes of mechanical design, manufacturing, and assembly. I. Design datum: The essential coordinates on the drawings. As the name implies, a design datum is a reference used during the part design phase to determine the positions of other points, lines, and surfaces. It reflects the design requirements of the part; it is the starting point for specifying the design dimensions and also a key reference point throughout the entire design process. The selection of the design basis has a direct impact on the machining accuracy and assembly quality of parts, therefore it must be chosen carefully. Design criteria are usually clearly indicated on the part drawings and serve as an important basis in the design and manufacturing processes. For example, in the design of shaft components, the centerline of the shaft is usually chosen as the design reference to ensure the coaxiality and positional accuracy of various holes, grooves, and other features on the shaft. In the design of box-type components, the symmetrical center plane of the box or the center line of important holes may be chosen as the design reference point to ensure the assembly accuracy between various components and the stability of the overall structure. The selection of a design basis requires taking various factors into consideration, including the assembly requirements of the parts, the processing sequence, and the convenience of measurement. From the perspective of assembly requirements, the design basis should be able to reflect the actual structural status and function of the parts within the overall machine. At the same time, the selection of design criteria should also take into account deformation and errors during the machining process, to ensure that the finished parts meet the design requirements. In practical mechanical design, determining the design benchmarks is often a complex process. Designers need to take into comprehensive consideration factors such as the function, structure, material, and manufacturing process of the parts, in order to ensure the rationality and effectiveness of the design criteria. Furthermore, with the development of computer-aided design technology, designers can use CAD software for 3D modeling and simulation analysis to determine design criteria in a more intuitive and accurate manner. II. Process datum: A guiding beacon in machining and assembly. The process datum is a reference point utilized during the machining and assembly of parts; it is also known as the manufacturing datum. It is primarily used to guide the positioning, measurement, and assembly of parts, ensuring machining precision and assembly quality. Process benchmarks are further subdivided into operation benchmarks, positioning benchmarks, measurement benchmarks, and assembly benchmarks, etc. The process standard is used to specify the dimensions and geometric tolerances for processing in this step, and it serves as an important guide for the manufacturing process. In machining, the selection of process references directly affects machining accuracy and efficiency. Therefore, when selecting a process benchmark, it is necessary to take into comprehensive consideration factors such as the part’s structure, processing equipment, manufacturing processes, and measurement requirements. Positioning references are used to place the workpiece in the correct position on the machine tool or in the fixture; they are key to ensuring machining accuracy and safety. The selection of positioning references should follow the principles of reference coincidence, consistency of references, and ease of clamping. In actual machining, the selection of a positioning datum often needs to be flexibly adjusted according to the structural characteristics and machining requirements of the part. For example, when machining shaft components, the center line of the shaft can be chosen as the positioning reference ； When machining box-type parts, the symmetrical center plane of the box or the center line of important holes can be chosen as the positioning reference. Measurement references are used to check the dimensions and position of the machined surfaces, and they serve as an important basis for determining whether a part meets quality standards. The selection of a measurement reference should follow principles such as ease of measurement, high accuracy, and good stability. In actual measurements, the selection of a measurement reference often requires comprehensive consideration based on the structural characteristics of the part and the measurement requirements. For example, when measuring the coaxiality of shaft-type parts, the centerline of the shaft can be chosen as the measurement reference ； When measuring the parallelism of box-type parts, the symmetrical center plane of the box or the center line of important holes can be chosen as the measurement reference. Assembly references are used to determine the relative position of parts within assemblies or products, and they are key to ensuring assembly accuracy and efficiency. The selection of assembly references should follow principles such as ease of assembly, high precision, and good stability. In actual assembly, the selection of assembly references often requires comprehensive consideration based on the structural characteristics of the product and the assembly requirements. For example, when assembling an engine, the center line of the crankshaft can be chosen as the assembly reference ； When assembling the transmission, the centerlines of the input and output shafts can be chosen as the assembly reference. III. Relationship and Coordination between Design Bases and Process Bases Design bases and process bases play irreplaceable roles in mechanical design, but they are not isolated from one another. In practical mechanical design, the design datum and the process datum need to be coordinated with each other to ensure the smooth progress of the entire design, manufacturing, and assembly process. First, the design criteria and process criteria should overlap as much as possible. This can reduce the errors caused by the conversion reference, thereby improving machining precision and assembly quality. However, due to limitations in technology and cost, sometimes the design benchmarks and process benchmarks may not align perfectly. In such cases, adjustments and compensations must be made through reasonable process planning and measurement methods to ensure machining accuracy and assembly quality. Secondly, the selection of design and process criteria should take into account deformation and errors during the machining process. In machining, due to various factors, parts often experience deformation and errors. Therefore, when selecting design and process criteria, it is necessary to fully take these factors into account and take appropriate measures to reduce the impact of deformation and errors. For example, when machining slender shafts, auxiliary devices such as tailstocks or centering fixtures can be used to reduce the impact of deformation and errors ； When machining box-type parts, reasonable processing techniques and measurement methods can be employed to reduce the impact of deformation and errors. Finally, the selection of design criteria and process criteria should take into account factors such as cost-effectiveness and production efficiency. In mechanical design and manufacturing, economy and production efficiency are very important considerations. Therefore, when selecting design and process parameters, it is necessary to take into account factors such as processing costs, processing time, processing equipment, and measurement requirements, in order to minimize processing costs and improve production efficiency while still meeting the design requirements. IV. Conclusion Design criteria and process criteria play irreplaceable roles in mechanical design. The design basis is the essential coordinate on the drawings, used to determine the design requirements and manufacturing criteria for the parts ； Process benchmarks serve as guiding beacons in machining and assembly, used to guide the positioning, measurement, and assembly of parts. In practical mechanical design, the design datum and the process datum need to be coordinated with each other to ensure the smooth progress of the entire design, manufacturing, and assembly process. With the development of computer-aided design and manufacturing technologies as well as intelligent manufacturing technologies, the selection and application of design criteria and process criteria will become more intelligent and automated. In the future, mechanical designers will be able to use more advanced CAD software and simulation analysis techniques to determine design and manufacturing criteria, thereby improving design accuracy and production efficiency. At the same time, with the continuous development of intelligent manufacturing technologies, mechanical processing and assembly processes will become more intelligent and automated, thereby further improving processing accuracy and assembly quality. Therefore, as mechanical designers and manufacturing engineers, we need to continuously learn and master new design and manufacturing technologies and methods in order to better address the increasingly complex and diverse challenges in mechanical design and manufacturing. At the same time, we also need to focus on accumulating and summarizing practical experience in order to continuously improve our design and manufacturing skills.