GB/T 32.2-2025Fasteners - Hexagon head bolts with split pin hole on head - Part 2: Reduced shank - Product grade B (English PDF)

Foreword

GB/T 32.2-2025 was issued on 5 October 2025 by the State Administration for Market Regulation and the Standardization Administration of the People's Republic of China, and has been in force since 1 February 2026. The /T in the designation marks it as a recommended national standard.

This document was drafted in accordance with the rules given in GB/T 1.1-2020 Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.

This document is Part 2 of the GB/T 32 series of national standards, Hexagon head bolts with split pin hole on head. The following parts of GB/T 32 have been published: GB/T 32.1 Hexagon head bolts with split pin hole on head; GB/T 32.2 Fasteners - Hexagon head bolts with split pin hole on head - Part 2: Reduced shank - Product grade B; GB/T 32.3 Hexagon head bolts with split pin hole on head - Fine pitch thread.

This document replaces GB/T 32.2-1988 Hexagon head bolts with split pin hole on head - Reduced shank - Product grade B. Compared with GB/T 32.2-1988, apart from structural adjustments and editorial changes, the main technical changes are as follows: a) the sizes M7 and M18 have been added in accordance with GB/T 5784 (see Table 1); b) a table of technical requirements and referenced standards has been added (see Table 2); c) marking and labelling have been added (see Clause 6).

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.

This document was proposed by the China Machinery Industry Federation and is under the jurisdiction of the National Technical Committee on Fasteners of Standardization Administration of China (SAC/TC 85), which is responsible for its interpretation.

Drafting organizations: Ningbo Jiulong Chuangzhan Fastener Co., Ltd., China Machinery Productivity Promotion Center Co., Ltd., CGN Wind Power Co., Ltd., Shandong Jiujia Fastener Co., Ltd.

The previous editions of this document and of the documents it replaces: first published in 1958 as GB/T 32-1958 and first revised in 1976; at the second revision, in 1988, parts of GB/T 25-1976 Small hexagon head bolts with split pin hole on head (itself preceded by GB/T 25-1958 and GB/T 25-1966) and of GB/T 26-1976 Small hexagon head fitted bolts with split pin hole on head (preceded by GB/T 26-1958 and GB/T 26-1966) were merged into it, and it was revised as GB/T 32.2-1988; this is the third revision.

Introduction

The GB/T 32 series of national standards, Hexagon head bolts with split pin hole on head, aims to standardize the types, dimensions and technical requirements of hexagon head bolts with a hole in the head, and consists of three parts. GB/T 32.1 Hexagon head bolts with split pin hole on head aims to standardize the types, dimensions, technical requirements, marking, labelling and designation of such bolts in product grades A and B. GB/T 32.2 Fasteners - Hexagon head bolts with split pin hole on head - Part 2: Reduced shank - Product grade B does the same for reduced shank bolts of product grade B. GB/T 32.3 Hexagon head bolts with split pin hole on head - Fine pitch thread does the same for fine pitch thread bolts of product grades A and B.

Hexagon head bolts with a hole in the head are commonly used to prevent the loosening of mechanical fastenings, that is, the bolts are fixed to one another by a mechanical fixing element so that they cannot come loose.

At installation, low-carbon metal wire is passed through the holes in the heads of the hexagon bolts so that several bolts are linked in series and locked together. The locking effect is good, and the method is used for closely grouped bolted joints that are not frequently dismantled.

1 Scope

China's national standard for the reduced shank hexagon head bolt with a wire hole drilled through its head, product grade B. The hole is there for locking: after tightening, a length of soft low-carbon wire is threaded through the heads of several neighbouring bolts and twisted, so that no single bolt can turn back without pulling against the others. It is the traditional answer to loosening in closely spaced groups of bolts that are rarely taken apart, where a lock washer or a prevailing torque nut is not enough or not wanted. The bolt itself is the reduced shank bolt of GB/T 5784, whose shank is about the pitch diameter of the thread; this part adds only the hole, fixing its diameter and its position in the head, and then sets out the technical requirements by reference to the general fastener standards, the product marking and packaging label, and the designation. It covers coarse thread sizes M6 to M20 in steel property classes 5.8, 6.8 and 8.8 and stainless steel A2-50 and A2-70. The 2025 edition replaces GB/T 32.2-1988, adds the M7 and M18 sizes in line with GB/T 5784, and adds the table of technical requirements and the clause on marking and labelling that the old edition lacked.

This document specifies the types and dimensions, technical requirements, marking and labelling, and designation of reduced shank hexagon head bolts with a hole in the head.

This document applies to coarse thread hexagon head bolts with a hole in the head, with thread sizes M6 to M20, property classes 5.8, 6.8, 8.8, A2-50 and A2-70, a shank diameter approximately equal to the pitch diameter of the thread, and product grade B (hereinafter referred to as bolts).

The bolts specified in this document are products complying with GB/T 5784 with a wire hole made in the head.

2 Normative references

The contents of the following documents constitute indispensable provisions of this document through normative references in the text. For dated references, only the edition corresponding to that date applies to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 90.1 Fasteners - Acceptance inspection.

GB/T 90.2 Fasteners - Marking and packaging.

GB/T 197 General purpose metric screw threads - Tolerances.

GB/T 1237 Designation system for fasteners.

GB/T 3098.1 Mechanical properties of fasteners - Bolts, screws and studs.

GB/T 3098.6 Mechanical properties of fasteners - Stainless steel bolts, screws and studs.

GB/T 3099.4 Terminology of fasteners - Control, inspection, delivery, acceptance and quality.

GB/T 3103.1 Tolerances for fasteners - Bolts, screws, studs and nuts.

GB/T 5267.1 Fasteners - Electroplated coating systems.

GB/T 5267.2 Fasteners - Non-electrolytically applied zinc flake coating systems.

GB/T 5276 Fasteners - Bolts, screws, studs and nuts - Symbols and descriptions of dimensions.

GB/T 5278 Fasteners - Split pin holes and wire holes.

GB/T 5779.1 Fasteners - Surface discontinuities - Bolts, screws and studs for general requirements.

GB/T 5784 Fasteners - Hexagon head bolts - Reduced shank - Product grade B.

GB/T 16938 Fasteners - General technical specifications for bolts, screws, studs and nuts.

3 Terms and definitions

There are no terms and definitions to be defined in this document.

4 Types and dimensions

The type of the bolts shall be as shown in Figure 1 and the dimensions as given in Table 1; the other types and dimensions shall comply with GB/T 5784. Symbols and descriptions of dimensions are in accordance with GB/T 5276.

Figure 1 shows the hexagon head bolt with the wire hole drilled across the head. Table 1 gives, for each thread size from M6 to M20, the thread pitch, the diameter of the wire hole as a maximum and as a nominal (minimum) value, and the approximate distance h locating the hole in the head, in millimetres. The sizes M7, M14 and M18 are shown in brackets as non-preferred sizes.

5 Technical requirements

The bolts shall comply with the technical requirements given in Table 2 and in the standards listed there.

Table 2 sets out the requirements separately for steel and for stainless steel bolts: general requirements in accordance with GB/T 16938; thread tolerance in accordance with GB/T 197; mechanical properties in property classes 5.8, 6.8 and 8.8 in accordance with GB/T 3098.1 for steel, and in steel group and property classes A2-50 and A2-70 in accordance with GB/T 3098.6 for stainless steel; tolerances of product grade B in accordance with GB/T 3103.1, except as specified in Clause 4; the wire hole in accordance with GB/T 5278; surface finish; surface discontinuities in accordance with GB/T 5779.1 for steel and by agreement for stainless steel; and acceptance and packaging in accordance with GB/T 90.1 and GB/T 90.2.

For surface finish, steel bolts are supplied plain (without coating), with electroplating in accordance with GB/T 5267.1, or with a non-electrolytically applied zinc flake coating in accordance with GB/T 5267.2; stainless steel bolts are supplied plain (cleaned and polished) and/or passivated. Other technical requirements or surface treatments shall be agreed between supplier and purchaser.

The notes to Table 2 add that the thread tolerance position of uncoated fasteners may be specified in the relevant coating standard according to the type of coating; that the most commonly used stainless steel groups are A2 and A4, but other groups of GB/T 3098.6 suited to corrosive environments may be needed depending on service conditions, with GB/T 3098.24 giving mechanical properties for use at elevated temperatures and GB/T 3098.25 guidance on selecting stainless steel groups; that GB/T 5267.4 gives the passivation method; and that GB/T 5779.1 may be referred to for surface discontinuities of stainless steel bolts.

7 Designation

The designation requirements specified in GB/T 1237 apply to all sizes: the property class marking symbol of steel fasteners is in accordance with GB/T 3098.1, and the steel group and property class marking symbol of stainless steel fasteners in accordance with GB/T 3098.6.

Where the type of surface finish is not stated in the designation, steel fasteners are delivered plain and stainless steel fasteners are delivered in the simple treated (cleaned and polished) condition.

Example: a reduced shank hexagon head bolt with a wire hole in the head, thread size M12, nominal length l = 80 mm, property class 8.8, plain finish, product grade B, with a 2.0 mm wire hole in the head, is designated: Bolt GB/T 32.2 M12x80.

Bibliography

[1] GB/T 3098.24 Mechanical properties of fasteners - Stainless steel and nickel alloy bolts, screws, studs and nuts for high temperature applications.

[2] GB/T 3098.25 Mechanical properties of fasteners - Guidelines for the selection of stainless steels and nickel alloys for fasteners.

[3] GB/T 5267.4 Fasteners - Surface treatment - Passivation of corrosion-resistant stainless steel parts (GB/T 5267.4-2009, ISO 16048:2003, IDT).