Reasonable determination of grinding allowance is of great significance to improve productivity and ensure processing quality. Generally speaking, grinding is a finishing process. Compared with other cutting methods, its cutting efficiency is much lower. If the allowance is too large, the production rate will be significantly reduced, and the power consumption of the grinding wheel and the machine tool will be increased. In some cases, it will even reduce the quality of parts. For example, for workpieces that have undergone surface nitriding and high-frequency heat treatment, the hardness of the surface layer is the highest, and the hardness is the lowest as it goes inward. The hardness of the surface layer does not meet the requirements. However, the allowance should not be too small, otherwise the processing traces or defective layers left by the previous process cannot be ground away. Therefore, the basic principle for determining the grinding allowance should be: under the premise of ensuring the quality of the surface layer of the workpiece after grinding, the smaller the grinding allowance, the better.
Due to the complexity of the influence on the machining allowance, it is difficult to specify a unified calculation method. Usually, it can be determined by looking up the table from the relevant manual and combining the specific conditions of the agent site. The data listed below are for reference:
When the shaft diameter d<80mm, the ratio of length l to diameter d l/d<10, the grinding allowance after semi-finishing is generally 0.30~0.50mm. The smaller l/d and the hardened workpiece should take a smaller value.
The processing allowance left for fine grinding after rough grinding, if no other intermediate process is carried out between rough grinding and fine grinding, generally 0.03~0.08mm is acceptable; if rough grinding is followed by other processes, such as turning, milling, heat treatment etc., the fine grinding allowance can be taken as 0.15~0.25mm. If the workpiece needs nitriding after rough grinding, the fine grinding allowance can be about 0.10mm.
