GB/T 21470-2008 in English

《GB/T 21470-2008锤上钢质自由锻件机械加工余量与公差 盘、柱、环、筒类》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。
本标准规定了盘、柱、戴孔圆盘、圆环、套筒等各类自由锻件的加工余量与公差。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 of disks, columns, disks with holes, rings, seamless cylindrical sleeves, etc.

This standard is applicable to the 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%.

The allowances and tolerances for open die forgings beyond the scope specified in this standard shall be determined by the supplier and the purchaser through negotiation.

2 Normative References

The following documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments (excluding corrections) to, or revisions of, any of these publications do not apply. However, all parties coming to an agreement according to this standard are encouraged to investigate the possibility of applying the latest editions of these documents. For undated references, the latest edition applies to this standard.

GB/T 21469 Machining Allowances and Tolerances for Steel Open Die Forgings on Hammer - General Requirement
JB/T 9179.4 Machining Allowance and Tolerance of Open Die Forgings on Hydraulic Press - Disk and Punched Hole
JB/T 9179.5 Machining Allowance and Tolerance of Open Die Forgings on Hydraulic Press - Short Round Shaft
JB/T 9179.7 Machining Allowance and Tolerance of Open Die Forgings on Hydraulic Press - Cylinder
JB/T 9179.8 Machining Allowance and Tolerance of Open Die Forgings on Hydraulic Press – Ring

3 Disks and Columns

3.1 The dimensions of open die disk forgings with round, rectangular (A1/A2≤2.5) and hexagonal cross-sections shall satisfy 0.1D≤H≤D (or A1, S); the dimensions of open die column forgings with round, rectangular (A1/A2≤2.5) and hexagonal cross-sections shall satisfy D
3.2 The machining allowances and tolerances for open die forgings of disks and columns shall be in accordance with Figure 1 and Table 1.

3.3 The rest shall be in accordance with GB/T 21469.

Foreword II
1 Scope
2 Normative References
3 Disks and Columns
4 Disks with Holes
5 Rings
6 Seamless Cylindrical Sleeves
Annex A (Informative) Examples of Calculation of Dimensions for Open Die Ring Forgings of Rings
Annex B (Informative) Examples of Calculation of Dimensions for Open Die Forgings of Seamless Cylindrical Sleeves