Two minute understanding, three methods for determining machining allowance in precision parts processing

When determining the machining allowance for precision parts processing, the total machining allowance (blank allowance) and machining allowance should be determined separately. The size of the total machining allowance is related to the manufacturing accuracy of the selected blank. When using the table lookup correction method to determine the machining allowance, the rough machining process cannot be determined using the table lookup correction method, but must be obtained by subtracting the sum of other machining allowances from the total machining allowance.

1. Empirical estimation method, which estimates machining allowances based on the practical experience of craftsmen. To avoid waste caused by insufficient margin, it is estimated that the margin is generally too large. This method is only used for single piece small batch production.

2. The table lookup correction method is used to compile the processing allowance data accumulated in factory production practice and experimental research into tables and manuals. When determining the machining allowance for precision parts, the required data can be checked from the manual first, and then appropriate corrections can be made based on the actual situation of the factory. This method is currently the most widely used. When checking the table, it should be noted that the margin value in the table is the basic margin value. The machining allowance for symmetrical surfaces is bilateral allowance, while the allowance for asymmetrical surfaces is unilateral allowance.

3. Analytical calculation method, which is a method of determining machining allowance based on the above formula for machining allowance calculation and certain experimental data, comprehensively analyzing and calculating various factors that affect machining allowance. The machining allowance determined by this method is relatively economical and reasonable, but comprehensive and reliable experimental data must be available. At present, this method is only used in factories with very expensive materials, as well as in military or a few batch production factories.