Method for Determining Machining Allowance in Precision Parts Processing

When determining the machining allowance in 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 lookup table correction method to determine the machining allowance, the rough machining process cannot be determined using the lookup table 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 the machining allowance based on the actual experience of the craftsman. To avoid waste caused by insufficient gross profit, it is estimated that the gross profit is generally higher. This method is only used for single piece small batch production.

2. The table lookup and 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 in precision parts processing, the required data can be found in the manual first, and then adjusted appropriately according to the actual situation of the factory. This method is currently the most widely used. When looking up a table, it should be noted that the margin value in the table is the basic margin value. The machining allowance for symmetric planes is bilateral allowance, while the machining allowance for asymmetric planes is unilateral allowance.

3. Analysis calculation method refers to the 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 factories that produce military or small quantities.