Introduction to Machining Benchmarks

concept


Mechanical parts are composed of several surfaces. To study the relative relationship of the surface of the parts, it is necessary to recognize a datum. The datum is the point, line, and surface on which the orientation of other points, lines, and surfaces are recognized on the part. According to the different functions of benchmarks, benchmarks can be divided into planning benchmarks and process benchmarks.


Classification


Planning datum: The datum used to recognize the orientation of other points, lines and surfaces on the part drawing is called the planning datum.


Technology benchmark: the benchmark used in the process of parts processing and equipment, called the process benchmark. Process benchmarks are divided into device benchmarks, measurement benchmarks and positioning benchmarks according to different uses.


(1) Device datum: The datum used to recognize the position of the part in the component or product when it is installed, called the device datum.


(2) Measurement datum: the datum used to check the size and orientation of the processed surface, called the measurement datum.


(3) Positioning datum: The datum used for positioning the workpiece during processing, called the positioning datum. The surface (or line, point) used as the positioning reference can only be selected from the unprocessed blank surface at the beginning of a process. This positioning surface is called the rough reference. In the subsequent processes, the processed surface can be used as the positioning reference. This positioning surface is called a fine datum.