GB/T 70.3-2023 PDF in English
GB/T 70.3-2023 (GB/T70.3-2023, GBT 70.3-2023, GBT70.3-2023)
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivered in | Name of Chinese Standard | Status |
| GB/T 70.3-2023 | English | 290 |
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Hexagon socket countersunk head screws with reduced loadability
| Valid |
| GB/T 70.3-2008 | English | 85 |
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Hexagon socket countersunk head screws
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| GB/T 70.3-2000 | English | 439 |
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Hexagon socket countersunk head screws
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Standards related to (historical): GB/T 70.3-2023
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GB/T 70.3-2023: PDF in English (GBT 70.3-2023) GB/T 70.3-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 21.060.10
CCS J 13
Replacing GB/T 70.3-2008
Hexagon Socket Countersunk Head Screws with Reduced
Loadability
(ISO 10642:2019, Fasteners – Hexagon Socket
Countersunk Head Screws with Reduced Loadability, MOD)
降低承载能力内六角沉头螺钉
ISSUED ON: MAY 23, 2023
IMPLEMENTED ON: DECEMBER 1, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 6
1 Scope ... 7
2 Normative References ... 7
3 Terms and Definitions ... 8
4 Type, Dimension and Head Inspection ... 8
5 Technical Conditions ... 16
6 Marking and Labelling ... 17
7 Designation ... 18
Annex A (Informative) Minimum Ultimate Tensile Loads for Bolts and Screws with
Full Loadability, Coarse Pitch Threads M2 and M2.5 ... 19
Bibliography ... 20
Foreword
This Document was drafted as per the rules specified in GB/T 1.1-2020 Directives for
Standardization – Part 1: Rules for the Structure and Drafting of Standardizing Documents.
This Document is Part 3 of GB/T 70 Hexagon Socket Screws (containing measuring gauge).
GB/T 70 has published the following parts:
--- GB/T 70.1 Hexagon Socket head Cap Screws;
--- GB/T 70.2 Hexagon Socket Button Head Screws;
--- GB/T 70.3 Hexagon Socket Countersunk Head Screws with Reduced Loadability;
--- GB/T 70.4 Hexagon Socket Button Head Screws with Collar;
--- GB/T 70.5 Gauging of Hexagon Sockets;
--- GB/T 70.6 Hexagon Socket Head Cap Screws – Fine Pitch Thread.
This Document replaced GB/T 70.3-2008 Hexagon Socket Countersunk Head Screws.
Compared with GB/T 70.3-2008, this Document has the major technical changes as follows
besides the structural adjustments and editorial modifications:
a) It is clearly stated that hexagon socket countersunk head screws have reduced loadability
due to their head design (head size and hexagon socket penetration depth) (see Clause 1
of this Edition; Clause 1 of the 2008 Edition);
b) Add M2 and M2.5. Since their minimum tensile loads are not specified in GB/T 3098.1
and GB/T 3098.6, the corresponding formulas are used for calculation (see Clause 1,
Table 1, Annex A of this Edition);
c) Add material and technical requirements for stainless steel screws (see Clause 1, Table 4,
Table 5 of this Edition);
d) Add head type details (see Figure 4 of this Edition);
e) Delete the shorter lengths of M4~M20 (see Table 1 of the 2008 Edition);
f) Increase the actual maximum value of dk (see Table 1 and Table 2 of this Edition);
g) Add head height kmin as the reference size (see Table 1 and Table 2 of this Edition);
h) Use the inner wrenching depth tmax to replace the wall thickness wmin between the
wrenching position and the supporting surface, which is consistent with the dimensioning
method for hexalobular wrenching (see Table 1, Table 2 of this Edition; Table 1 of the
2008 Edition);
i) For some threaded screws from M14 to M20, the reference value of thread length b is
increased to 3d, so these screws can be subjected to tensile tests in accordance with GB/T
3098.6 (for screws with reduced loadability, b ≥ 3d is required) (see Table 2 of this
Edition; Table 1 of the 2008 Edition);
j) Add Da, Dk and F as gauge dimensions (see Figure 5, Table 3 of this Edition; Figure 2,
Table 1 of the 2008 Edition);
k) Add marking and labeling requirements (see Clause 6 of this Edition).
This Document modified and adopted ISO 10642:2019 Fasteners – Hexagon socket
countersunk head with reduced loadability.
The technical differences and causes between this Document and ISO 10642:2019 are as
follows:
--- Use the normatively quoted GB/T 2 to replace ISO 4753 to adapt to China’s technical
conditions (see Figure 1);
--- Use the normatively quoted GB/T 16938 to replace ISO 8992 to adapt to China’s
technical conditions (see Table 4);
--- Use the normatively quoted GB/T 197 to replace ISO 965-1 to adapt to China's technical
conditions (see Table 4);
--- Use the normatively quoted GB/T 3098.1 to replace ISO 898-1 to adapt to China's
technical conditions (see Table 4, Clause 6, Clause 7);
--- Use the normatively quoted GB/T 3098.6 to replace ISO 3506-1 to adapt to China's
technical conditions (see Table 4, Clause 6, Clause 7);
--- Use the normatively quoted GB/T 3103.1 to replace ISO 4759-1 to adapt to China's
technical conditions (see Table 4);
--- Use the normatively referenced GB/T 5267.1 to replace ISO 4042 to adapt to China’s
technical conditions (see Table 4);
--- Use the normatively quoted GB/T 5267.2 to replace ISO 10683 to adapt to China’s
technical conditions (see Table 4);
--- Use the normatively quoted GB/T 5779.1 to replace ISO 6157-1 to adapt to China's
technical conditions (see Table 4);
--- Use the normatively quoted GB/T 5779.3 to replace ISO 6157-3 to adapt to China's
technical conditions (see Table 4);
--- Use the normatively referenced GB/T 90.1 to replace ISO 3269 to adapt to China’s
Hexagon Socket Countersunk Head Screws with Reduced
Loadability
1 Scope
This Document specifies the type, dimensions, technical conditions, marking, labels and signs
of hexagon socket countersunk head screws with reduced loadability due to head design.
This Document is applicable to hexagon socket countersunk head screws with thread
specifications M2~M20; coarse threads; performance levels 8.8, 10.9 and 12.9; groups and
performance levels A2-50, A4-50, A2-70, A4-70, A2-80 and A4-80, and Level-A products.
NOTE 1: For other size options, see GB/T 2, GB/T 197 and GB/T 3106.
NOTE 2: Reduced loadability (related to the combination of countersunk head size and hexagonal
penetration depth specified in this Document) implies a limit to the minimum tensile load (see Table 5).
NOTE 3: Special attention needs to be paid to ensure that the countersunk head is aligned with the
countersunk hole support surface in the assembly.
2 Normative References
The provisions in following documents become the essential provisions of this Document
through reference in this Document. For the dated documents, only the versions with the dates
indicated are applicable to this Document; for the undated documents, only the latest version
(including all the amendments) is applicable to this Document.
GB/T 2 Fasteners – Ends of Parts with External Thread (GB/T 2-2016, ISO 4753:2011,
MOD)
GB/T 90.1 Fasteners – Acceptance Inspection (GB/T 90.1-2023, ISO 3269:2019, MOD)
GB/T 90.2 Fasteners – Marking and packaging
GB/T 197 General purpose metric screw threads – Tolerances (GB/T 197-2018, ISO 965-
1:2013, MOD)
GB/T 1237 Designation system for fasteners (GB/T 1237-2000, eqv ISO 8991:1986)
GB/T 3098.1 Mechanical properties of fasteners - Bolts, screws and studs (GB/T 3098.1-
2010, ISO 898-1:2009, MOD)
GB/T 3098.6 Mechanical properties of fasteners - Stainless steel bolts, screws and studs
(GB/T 3098.6-2023, ISO 3506-1:2020, MOD)
GB/T 3099.4 Terminology of fasteners - Control, inspection, delivery, acceptance and
quality (GB/T 3099.4-2021, ISO 1891-4:2018, MOD)
GB/T 3103.1 Essential oils and aromatic extracts - Determination of residual benzene
content (GB/T 3103.1-2002, idt ISO 4759-1:2000)
GB/T 5267.1 Fasteners - Electroplate coating (GB/T 5267.1-2023, ISO 4042:2022, MOD)
GB/T 5267.2 Fasteners - Non-electrolytically applied zinc flake coatings (GB/T 5267.2-
2021, ISO 10683:2018, MOD)
GB/T 5276 Fasteners - Bolts, screws, studs and nuts - Symbols and descriptions of
dimensions (GB/T 5276-2015, ISO 225:2010, MOD)
GB/T 5779.1 Fasteners-Surface discontinuities - Bolts, screws and studs for general
requirements (GB/T 5779.1-2000, idt ISO 6157-1:1988)
GB/T 5779.3 Fasteners - Surface discontinuities - Bolts, screws and studs for special
requirements (GB/T 5779.3-2000, idt ISO 6157-3:1988)
GB/T 16938 Fasteners - General requirements for bolts screws studs and nuts (GB/T
16938-2008, ISO 8992:2005, IDT)
3 Terms and Definitions
For the purposes of this Document, no terms and definitions apply.
4 Type, Dimension and Head Inspection
4.1 Type and dimension
The type of screw shall be as per the Figures 1~4; dimension of screw shall be as per Tables
1~2.
The dimension code and labelling shall be as stipulated in GB/T 5276.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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