Tolerance setting and control of machining

As a person engaged in machining, a reasonable design of the machining tolerances of products is conducive to the processing and quality assurance of parts. The relationship between machining tolerances and machining allowances is often misunderstood, resulting in poor machining and unreasonable tolerances , unable to meet the drawing requirements of the part, and finally scrapped.

For the design of mechanical parts, firstly, from the perspective of assembly, the corresponding tolerance standards should be given according to the fit of the parts. For parts in the machining enterprise, the processing technology and surface treatment methods should be considered to design the corresponding processing tolerances. When the parts are roughed in the early stage, the general tolerances are relatively large, subject to the margin. In the finishing process, the type of surface treatment should be considered, and the dimensional tolerance of the finishing process should be designed according to the dimensional change of the surface treatment method In order to meet the precision of the product after finishing, many inexperienced process engineers are often easy to control the dimensional tolerance according to the requirements of the customer’s drawing during the finishing process, ignoring the dimensional influence brought by the surface treatment, and finally lead to Tolerance cannot be guaranteed, repaired or scrapped.

machining tolerances must be set in conjunction with the production process and surface treatment. If the assembly process is involved, the dimensional changes of the assembly should also be considered, what kind of assembly method to choose, and different assembly methods have different dimensional changes. These need to be judged based on actual changes or experience. The surface treatment methods are the same, and different surface treatment companies have different pH and actual changes.