GB/T 21469-2008 PDF English
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| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB/T 21469-2008 | English | 130 |
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Machining allowances and tolerances for steel open die forgings on hammer -- General requirement
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GB/T 21469-2008: Machining allowances and tolerances for steel open die forgings on hammer -- General requirement
---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT21469-2008
GB
NATIONAL STANDARD OF THE
PEOPLE'S REPUBLIC OF CHINA
ICS 77.140.85
J 32
Replacing GB/T 15826.1-1995
Machining allowances and tolerances for steel open die
forgings on hammer - General requirement
Issued on. FEBRUARY 28, 2008
Implemented on. AUGUST 1, 2008
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword... 3
1 Scope... 4
2 Normative references... 4
3 Terminology... 4
4 Technical requirements... 5
Foreword
This standard is a revision of GB/T 15826.1-1995 Machining allowances and
tolerances for steel open die forgings on hammer - General requirement.
Compared with GB/T 15826.1-1995, the main changes of this standard are as follows.
-- The foreword is added.
-- English annotations for terms are added.
This standard was proposed by the China Machinery Industry Federation.
This standard is under the jurisdiction of the National Technical Committee on Forging
and Stamping of Standardization Administration of China.
Drafting organizations of this standard are Shanghai Hudong Forging Factory and
Pinghu Chenren Meter Co., Ltd.
The main drafters of this standard are Sun Changfen and Dong Zhusheng.
The previous versions of the standards replaced by this standard are as follows.
-- GB/T 15826.1-1995.
Machining allowances and tolerances for steel open die
forgings on hammer - General requirement
1 Scope
This standard specifies the general requirements for the machining allowances and
tolerances of steel open die forgings on hammer and their use.
This standard applies to open die forgings of carbon steel and alloy steel with a carbon
content not exceeding 0.9% and a total content of other alloy components not exceeding
4%.
For open die forgings that exceed the scope specified in this standard, the machining
allowance and tolerance shall be determined by the supplier and the buyer through
separate negotiation.
2 Normative references
The clauses in the following documents become the clauses of this standard through
reference in this standard. For all the referenced documents with dates, all the
subsequent amendments (excluding errata) or revisions are not applicable to this
standard. However, the parties who reach an agreement based on this standard are
encouraged to study whether the latest versions of these documents can be used. For all
the referenced documents without dates, the latest versions are applicable to this
standard.
GB/T 8541 Terminology of forging and stamping
3 Terminology
3.1 Basic terms
The definitions of nominal dimensions of forgings, forging tolerances, steps, hubs,
forgings without machining and forging drawings shall be in accordance with the
provisions of GB/T 8541.
3.2 Other terms
3.2.1 machining allowance
In order to make the parts have a certain processing size and surface roughness, on the
forging, a layer of metal for machining is left on the part surface that needs to be
machined, which is called machining allowance (see Figure 1).
3.2.2 excess metal
In order to simplify the shape of forgings and the forging process, some metal larger
than the machining allowance is added to certain parts of the forgings. This added metal
is called excess metal (see Figure 1).
3.2.3 flange
A step on a forging whose length is less than 0.5 times its own diameter and whose
diameter is greater than 1.5 times the diameter of the adjacent two ends is called a flange (see Figure 1).
4 Technical requirements
4.1 The machining allowances and tolerances specified in this standard are divided into two grades.
Grade F is used for forgings with general precision; Grade E is used for forgings with
higher precision.
NOTE. Grade E often requires special tooling and increased forging processing costs and is therefore
used for larger production runs.
4.2 Unless otherwise specified, the shape and position tolerances of open die forgings
Machining allowance
4.3 The machining allowances and tolerances specified in this standard are applicable
to forgings made from rolled products. When forging with steel ingots, the allowances
and upper deviations (lower deviations for inner holes and recesses) are allowed to be
increased by 50% according to the values in this standard (not applicable to the
determination of machining allowances and tolerances for the outer diameter of shaft
parts).
4.4 The allowances specified in this standard do not include the allowances for rough
machining of machining chucks, heat treatment chucks, materials for physical and
chemical testing, and final heat treatment (quenching and tempering, etc.). These
allowances shall be added according to the requirements of the purchaser.
4.5 For shaft parts (including smooth shafts, stepped shafts and crank shafts), the length
of the forging can be rounded to the nearest 0 or 5 mm, according to the principle "when
the last digit (n) of the integer is 0< n< 3 or n≥8, the length value is rounded to the nearest
0 mm, and when the last digit (n) is 3≤n< 5 or 5< n< 8, rounded to the nearest 5 mm".
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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