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GB/T 5779.3-2000 PDF in English


GB/T 5779.3-2000 (GB/T5779.3-2000, GBT 5779.3-2000, GBT5779.3-2000)
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GB/T 5779.3-2000: PDF in English (GBT 5779.3-2000)

GB/T 5779.3-2000
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 21.060.10
J 13
idt ISO 6157-3:1988
Fasteners - Surface discontinuities - Bolts, screws and studs
for special requirements
ISSUED ON: SEPTEMBER 26, 2000
IMPLEMENTED ON: FEBRUARY 01, 2001
Issued by: State Bureau of Quality Technical Supervision
Table of Contents
Foreword ... 3 
ISO foreword ... 4 
1 Scope ... 5 
2 Normative references ... 6 
3 Types, causes, appearance characteristics, limits of surface defects ... 6 
4 Inspection and judgment procedures ... 17 
Appendix A (Normative) Sampling scheme for surface defects ... 19 
NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA
Fasteners - Surface discontinuities
- Bolts, screws and studs for
special requirements
1 Scope
1.1 The limits, which are specified in this standard, apply to various types of surface
defects of bolts, screws, studs with special requirements.
Applicable bolts, screws, studs:
The nominal diameter of the thread is equal to or greater than 5 mm;
Product grades A and B;
Nominal length l ≤ 10d (or longer according to special requirements);
Performance grade 12.9;
Performance grades 8.8, 9.8, 10.9, but shall be specified in the product standard OR in
the agreement between the supplier and the buyer.
1.2 Even if the surface defects reach the allowable limits, which are specified in Chapter
3, the mechanical and working properties of the product shall still meet the minimum
requirements of GB/T 3098.1. In addition, it shall meet the dimensional requirements
of the corresponding product standards.
When the fatigue strength is required, the fatigue strength shall not be lower than that
which can be achieved by bolts without defects, in the same batch of products.
Note:
1 The Figures in Chapter 3 are examples only. They apply accordingly to other types of bolts,
screws, studs.
2 Some surface defects are exaggerated for clarity.
idt ISO 6157-3:1988
Replacing GB/T 5779.3-1986
2 Normative references
The following standards contain provisions which, through reference in this standard,
constitute provisions of this standard. At the time of publication, the editions indicated
were valid. All standards are subject to revision and parties using this standard should
explore the possibility of using the latest edition of the following standards.
GB/T 90-1985 Acceptance inspection, marking and packaging of fasteners (eqv ISO
3269:1984)
GB/T 1033-1995 Surface roughness parameters and their values (neq ISO 468:1982)
GB/T 2828-1987 Sampling procedures and tables for lot-by-lot inspection by
attributes (Apply to inspection of successive lots or batches)
GB/T 3098.1-2000 Mechanical properties of fasteners - Bolts, screws and studs (idt
ISO 898-1:1999)
GB/T 15239-1994 Sampling procedures and tables for isolated lot inspection by
attributes
3 Types, causes, appearance characteristics, limits of surface
defects
3.1 Cracks
A crack is a well-defined (crystalline) fracture, along or across a metal grain boundary,
which may contain inclusions of foreign elements. Cracks are usually caused by
excessive stress in the metal, during forging or other forming processes or heat
treatment. Cracks may also exist in the raw material. When the workpiece is reheated,
the cracks are usually discolored by peeling of the scale.
order.
4.2 Non-destructive inspection
A random sample is taken from the acceptance batch, to carry out visual or other non-
destructive inspection, such as magnetic technique or eddy current, as specified in Table
A1 of Appendix A (Normative). If it is found that the defective samples do not exceed
the allowable limit, the batch will be accepted (see also 4.4). If the number of defective
samples is found to exceed the allowable limit, these unqualified products will be
regarded as a batch and continue to be inspected, according to the procedure of 4.3.
4.3 Destructive inspection
According to the procedure of clause 4.2, if a non-conforming product is found, then
according to the provisions of Table A2 of Appendix A, the product with the most
serious defect will be formed into a second sample; a section perpendicular to the defect
will be taken, at the maximum depth passing through the defect, for inspection.
4.4 Judgment
If quenched cracks on any part OR folds on the interior corners OR folds below bearing
surface beyond the "clover leaf" shape are found on non-circular shoulder fasteners, in
the process of visual inspection, the batch of products will be rejected.
During destructive inspection, if forging cracks, bursts, seams and laps, voids, tool
marks or damage are found beyond the specified allowable limits, the batch will be
rejected.
0.08 x Head or flange diameter or
0.04 x Head or flange diameter
0.25 mm + 0.02 s (to spanner flat)
0.08 x Head or flange diameter or 0.04 x Head or flange diameter
0.25 x Socket depth
0.03 x Head diameter, maximum 0.13 mm
0.06 x Head diameter, maximum 1.6 mm
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.