（1） Process benchmark

Process benchmark refers to the benchmark used in the manufacturing process of a component. According to different purposes, process standards can be divided into process standards, positioning standards, measurement standards, and assembly standards.

1. Process benchmark

In the process diagram, the reference used to determine the size, shape, and position of the processed surface in this process is called the process reference.

2. Positioning benchmark
The reference used to determine the correct position of the workpiece on the machine tool or fixture during processing is called the positioning reference.

3. Measurement benchmark
The reference used to measure the shape, position, and dimensional errors of a workpiece during or after processing is called a measurement reference.

4. Assembly benchmark
The reference used to determine the relative position of parts or components on the product during assembly is called the assembly reference. The inner hole of a gear is the assembly reference for that gear. In general, the design benchmark is given on the part drawing, and the process benchmark is determined by the process personnel based on the specific process selection.

When analyzing benchmark issues, pay attention to the following two points:
1) The points, lines, and surfaces that serve as benchmarks may not necessarily exist specifically on the workpiece (such as hole centerlines, axis lines, etc.), but are reflected by certain specific surfaces, which are called base surfaces. For example, the centerline of the inner hole is reflected through the surface of the inner hole, where the centerline is the reference and the surface is the base. Therefore, the problem of selecting a benchmark is the problem of choosing an appropriate base surface. Specifically, sometimes for the convenience of description, benchmarks and basal planes can be collectively referred to as benchmarks.

2) As a benchmark, it can be a point and line without an area or a very small surface, but the base representing this benchmark always has a certain area. For example, installing a long axis on a lathe, with the axis as the reference and no surface area; The basal plane is a conical surface, which has a small area but does have a certain area.