Mechanical parts are made up of several surfaces to study the relative relationship of the surface of the part. ** Determine a reference. The reference is the point, line, and surface on which the position of the other points, lines, and faces are determined. Benchmarks can be divided into design benchmarks and process benchmarks based on the different functions of the benchmark.
Design basis: A reference used on a part drawing to determine the position of other points, lines, and faces is called a design basis.
Process Benchmark: The benchmark used by parts during machining and assembly, called the process baseline. Process benchmarks are divided into assembly benchmarks, measurement benchmarks, and positioning benchmarks depending on the application.
(1) Assembly basis: A reference used in assembly to determine the position of a part in a part or product, called an assembly basis.
(2) Measurement reference: A reference used to check the size and position of a machined surface, called the measurement reference.
(3) Positioning reference: The reference used for workpiece positioning during machining is called the positioning reference. As the surface (or line, point) of the positioning reference, only the unprocessed blank surface can be selected in the process. This positioning surface is called the rough reference. The processed surface can be used as the positioning reference in the subsequent processes. This positioning surface is called the fine reference.