GB/T 31.2-2025Fasteners - Hexagon head bolts with split pin hole on shank - Part 2: Reduced shank - Product grade B (English PDF)

Foreword

This document was drafted in accordance with the rules provided in GB/T 1.1-2020 Directives for Standardization - Part

1.Rules for the Structure and Drafting of Standardizing Documents. This is Part 2 of the series of national standards GB/T

31 Hexagon Head Bolts with Split Pin Hole on Shank. GB/T 31 has issued the following parts.

31.1 Hexagon Bolts with Split Pin Hole on Shank;

31.2 Fasteners - Hexagon Head Bolts with Split Pin Hole on Shank - Part 2. Reduced Shank - Product Grade B;

31.3 Fasteners - Hexagon Head Bolts with Split Pin Hole on Shank - Part

3.Fine Pitch Thread. This document serves as a replacement for GB/T 31.2-1988 Hexagon Bolts with Split Pin Hole on Shank - Reduced Shank - Product Grade B. In comparison with GB/T 31.2-1988, apart from structural adjustments and editorial modifications, the main technical changes are as follows:

a) In accordance with GB/T 5784, M7 and M18 specifications are added (see Table 1);

b) In accordance with the provisions for the "le" dimension in GB/T 5278, the "lh" dimension is modified (Table 1; Table 2 of Version 1988);

c) A Table of technical requirements and referenced standards is added (see Table 2);

d) "Markings and Labels" is added (see Chapter 6). Please be noted that certain content of this document may involve patents. The institution issuing this document does not undertake the responsibility of identifying these patents. This document was proposed by China Machinery Industry Federation. This document shall be under the jurisdiction of Technical Committee 85 on Fasteners of Standardization Administration of China (SAC/TC 85). The drafting organizations of this document. Ningbo Ningli High-strength Fastener Co., Ltd.; Shandong Gaoqiang Fastener Co., Ltd.; China Machinery Productivity Promotion Center Co., Ltd.; Beijing Gangcheng Petrochemical Equipment Parts Co., Ltd.; Anhui Anpute Fastening Technology Co., Ltd. This document is subject to interpretation by Technical Committee 85 on Fasteners of Standardization Administration of China. The issuing of the previous versions.

---First issued in 1958 as GB/T 31-1958, and first revised in 1976; Fasteners - Hexagon Head Bolts with Split Pin Hole on Shank - Part

1 Scope

GB/T 31.2-2025 is the Chinese national standard covering the hexagon bolt drilled through the shank for a split pin - the dimensions and tolerances of the reduced shank version in grade B, the hole position and size, and the mechanical properties. It replaces GB/T 31.2-1988, a standard thirty-seven years old. In force from 1 February 2026. Issued on 31 October 2025, it has been in force since 1 February 2026, replacing GB/T 31.2-1988.

This document specifies the types, dimensions, technical requirements, markings, labels and designation of hexagonal head bolts with split pin holes on shank, with reduced shank. This document applies to coarse-thread hexagonal head bolts with split pin holes on shank with thread specifications of M6 ~ M20, property grades of 5.8, 6.8, 8.8, A2-50 and A2-70, a shank diameter approximately equal to the thread pitch diameter, and a product grade of B (hereinafter referred to as the "bolts"). The bolts specified in this document have split pin holes formed in the shank section of the products specified in GB/T 5784.

2 Normative References

The contents of the following documents constitute indispensable clauses of this document through the normative references in the text. In terms of references with a specified date, only versions with a specified date are applicable to this document. In terms of references without a specified date, the latest version (including all the modifications) is applicable 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 3106 Fasteners - Bolts, Screws and Studs - Nominal Lengths and Thread Lengths

GB/T 5267.1 Fasteners - Electroplate Coating

GB/T 5267.2 Fasteners - Non-electrolytically Applied Zinc Flake Coatings

GB/T 5276 Fasteners - Bolts, Screws, Studs and Nuts - Symbols and Descriptions of Dimensions

GB/T 5278 Fasteners - Split Pin Holes and Wireholes

3 Terms and Definitions

This document does not have terms or definitions that need to be defined.