1.1 This part establishes limits for various types of surface discontinuities on nuts.
It applies to nuts with:
Nominal thread diameters from 5mm up to and including 39mm;
Product grades A and B;
All property classes according to GB/T 3098.2 and GB/T 3098.4, unless otherwise specified in product standards or agreed between supplier and purchaser.
1.2 Even if the surface defects reach the allowable limit specified in Chapter 3, the mechanical and working performance of the product should still meet the minimum requirements specified in GB/T 3098.2, GB/T 3098.4 and GB/T 3098.9. In addition, it should meet the size requirements of the corresponding product standards.
Notes:
1 The figures in Chapter 3 are only examples, and are applicable to other types of nuts accordingly.
2 For the sake of clarity, some surface defects are exaggerated in the figure.
2 Normative references
The following standards contain provisions which, through reference in this standard, constitute provisions of this standard. At the time of publication, all editions cited are valid. All standards are subject to revision, and all parties using this standard are encouraged to investigate the possibility of applying the latest editions of the following standards.
GB/T 90-1985 Acceptance inspection, marking and packaging of fasteners (eqv ISO 3269:1984)
GB/T 1031-1995 Surface roughness parameters and their values (neq ISO 468:1982)
GB/T 3098.2-2000 Mechanical properties of fasteners - Nuts - Coarse thread (idt ISO 898-2:1992)
GB/T 3098.4-2000 Mechanical properties of fasteners - Nuts - Fine pitch thread (idt ISO 898-6:1994)
GB/T 3098.9-1993 Mechanical properties of fasteners - Prevailing torque type steel hexagon nuts (eqv ISO 2320:1983)
GB/T 3098.12-1996 Mechanical properties of fasteners - Cone proof load test on nuts (idt ISO 10485:1991)
GB/T 3098.14-2000 Mechanical properties of fasteners - Widening test on nuts(idt ISO 10484:1997)
3 Types, causes, appearance and limits of surface discontinuities
3.1
cracks
a crack is a clean (crystalline) fracture passing through or across the grain boundaries and may possibly follow inclusions of foreign elements. Cracks are normally caused by overstressing the metal during forging or other forming operations, or during heat treatment, or may have been present in the raw material. Where parts are subjected to significant reheating, cracks are usually discoloured by scale
3.1.1
quench cracks
Foreword I ISO Foreword II 1 Scope 2 Normative references 3 Types, causes, appearance and limits of surface discontinuities 4 Inspection and evaluation procedure
