GB/T 21471-2008 in English

《GB/T 21471-2008锤上钢质自由锻件机械加工余量与公差 轴类》由TC74（全国锻压标准化技术委员会）归口，主管部门为国家标准化管理委员会。
本标准规定了光轴、台阶轴和单拐曲轴类自由锻件的机械加工余量与公差。本标准适用于含碳量不超过0.9%和其他合金成分总含量不超过4%的碳素钢和合金钢的自由锻件。

1 Scope

This standard specifies the machining allowances and tolerances for open die forgings - shaft without steps, shaft with steps and single throw crankshaft, as well as permissible limit deviation of forging without machining.

This standard is applicable to open die forgings of carbon steel and alloy steel with carbon content not exceeding 0.9% and the total content of other alloying constituents not exceeding 4%.

If the open die forging exceeds the specified range in this standard, its allowance and tolerance are determined through negotiation between the supplier and the purchaser separately.

2 Normative References

The following normative documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments (excluding corrections), or revisions, of any of these publications do not apply to this standard. However parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies.

GB/T 21469 Machining Allowances and Tolerances for Steel Open Die Forgings on Hammer - General Requirement
JB/T 9179.2 Machining Allowance and Tolerance of Open Die Forgings on Hydraulic Press - Round Shaft, Square Shaft and Rectangular Cross-section
JB/T 9179.3 Machining Allowance and Tolerance of Open Die Forgings on Hydraulic Press - Stepped Shaft

3 Open Die Forgings - Shaft without Steps

3.1 The dimension L of open die forgings - shaft without steps, with round, square, hexagon or rectangular (B/H ≤5) cross-section shall be greater than 2.5D (or A, B, S).

3.2 The machining allowances and tolerances for open die forgings - shaft without steps shall be in accordance with Figure 1 and Table 1.

Foreword i
1 Scope
2 Normative References
3 Open Die Forgings - Shaft without Steps
4 Open Die Forgings - Shaft with Steps
5 Open Die Forgings - Single Throw Crankshaft
6 Forging without Machining
Annex A (Informative) Examples for Calculation of Dimensions of Open Die Forgings - Shaft without Steps.