How to Calculate the Machining Allowance for Forging Parts?

The purpose of cutting stainless steel forgings is to make the dimensional accuracy and surface roughness of the parts meet the requirements. During the forging process, due to underpressure, forging die wear, upper and lower die shifts, oxidation and decarburization of stainless steel forgings, cooling shrinkage, etc., the size of stainless steel forgings is difficult to be accurate, and the shape may also be warped and twisted, and the surface roughness may not reach Defects such as requirements. Therefore, in the production of stainless steel forgings, an extra layer of metal should be left on the surface of the forging blank, which will be cut off during subsequent machining to ensure the processing quality of the stainless steel forgings. For some important load-bearing parts that require 100% sampling test or for the needs of inspection and machining positioning, excess metal should be left. Such excess metal is called margin.

A certain allowable error range is given on the basis of the nominal size of stainless steel forgings. This error range is called the tolerance of the forging. The single-sided allowance and tolerance are shown in the figure. There are two methods for determining the machining allowance and tolerance of stainless steel forgings. One is the method commonly used by forging factories to select according to the tonnage of the forging hammer, called the tonnage method. The second is to check the data according to the shape and size of the forging.