GB/T 12362-2003 in English

《GB/T 12362-2003钢质模锻件 公差及机械加工余量》由TC74（全国锻压标准化技术委员会）归口，主管部门为中国机械工业联合会。
本标准规定了钢质模锻件(以下简称锻件)的公差、机械加工余量及其使用原则。
本标准适用于模锻锤、热模锻压力机、螺旋压力机和平锻机等锻压设备生产的结构钢锻件。其他钢种的锻件亦可参照使用。本标准适用于质量小于或等于250 kg，长度，(最大尺寸)小于或等于2 500mm的锻件。

1 Scope

This standard specifies the tolerance, machining allowance and application principles of the steel die forging (hereinafter referred to as forging).
This standard is applicable to the structural steel forging produced by such forging and pressing equipments as the die forging hammer, hot press forging press, screw press and horizontal forging machine. The forging of other steel grades may also refer to this standard for application.
This standard is applicable to the forging that its mass is less than or equal to 250kg and its length (maximum dimension) is less than or equal to 2,500mm.

2 Classification of Tolerances and Machining Allowances

2.1 The tolerance in this standard shall be classified into: ordinary grade and fine grade.
The ordinary grade tolerance is applicable to the forging that can meet the technical requirements by adopting common die forging technology.
The fine grade tolerance is applicable to the forging that needs adopting additional fabrication technology to reach higher technical requirements. The fine grade tolerance may be used for either the full dimension or the partial dimension of a certain forging.
The horizontal forging only adopts ordinary grade tolerance.
2.2 Only Grade I machining allowance shall be adopted.

3 Technical Contents

3.1 Major Factors for Determination of Tolerance and Machining Allowance of Forging

3.1.1 Mass of forging mf
The estimation of mass of forging shall be conducted according to the following procedures:
Basic dimension of parts drawing→estimation of machining allowance→forging drawing→estimation of mass of forging. The tolerance and machining allowance shall be determined through table searching according to this mass.
3.1.2 Forging shape complexity coefficient S
The forging shape complexity coefficient is the ratio of the mass of forging mf and the mass mN of the outline container of the corresponding forging, which is detailed in Formula (1):

1 Scope
2 Classification of Tolerances and Machining Allowances
3 Technical Contents
3.1 Major Factors for Determination of Tolerance and Machining Allowance of Forging
3.2 Tolerance
3.3 Machining Allowance
Appendix A (Informative) Application Example of Tolerance of Forging