GB/T 10-2013Countersunk head square neck bolts (English PDF)

Foreword

This standard is one of the national bolt series standards, a series that includes GB/T 8, GB/T 10, GB/T 11, GB/T 12, GB/T 13, GB/T 14, GB/T 15, GB/T 27, GB/T 28, GB/T 29.1, GB/T 29.2, GB/T 31.1, GB/T 31.2, GB/T 31.3, GB/T 32.1, GB/T 32.2, GB/T 32.3, GB/T 35, GB/T 5780 to GB/T 5786, GB/T 5789, GB/T 5790, GB/T 16674.1 and GB/T 16674.2.

This standard was drafted in accordance with the rules given in GB/T 1.1-2009.

This standard replaces GB/T 10-1988 Countersunk head square neck bolts. The main changes with respect to GB/T 10-1988 are the following: the English title of the standard has been revised; the provision "commercial fastener varieties, which should be selected in preference" (Clause 1 of the 1988 edition) has been deleted; the normative references have been updated (Clause 2); the "general length range" has replaced the "commercial size range" (see Table 1); a table of general technical conditions has been added (see Table 2); and property class 3.6 has been withdrawn.

This standard 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).

The organisation responsible for drafting this standard is the China Machinery Productivity Promotion Centre; the participating drafting organisations are Ningbo Yonggang Fastener Co., Ltd. of the Ningbo Economic and Technological Development Zone and the Ningbo Fastener Industry Association.

The previous editions of the standard replaced by this standard are GB 10-1958, GB 10-1976 and GB/T 10-1988.

1 Scope

China's national standard for the countersunk head square neck bolt, one of the family of bolt standards that runs from GB/T 8 to GB/T 16674. The point of this particular bolt is the short square section under the head: it beds into a matching square hole, or into the wood or soft metal around a round one, so the bolt cannot turn while the nut is being tightened from the other side. That matters wherever there is no access to hold the head - carriage work, agricultural implements, conveyor belt splices, wooden structures - and the countersunk head lets the bolt finish flush with the surface, which is what a belt or a sliding load needs. The standard specifies the dimensions of the bolt, the general technical conditions and the reference standards for material, thread, mechanical property class, tolerances and surface finish, and the designation method with a worked example. It covers thread sizes from M6 to M20 in product grade C. The 2013 edition dropped the old commercial size range in favour of a general length range, added a table of general technical conditions and removed property class 3.6.

This standard specifies countersunk head square neck bolts with thread sizes from M6 to M20 and product grade C.

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 2 Fasteners - Ends of parts with external metric ISO thread.

GB/T 90.1 Fasteners - Acceptance inspection; GB/T 90.2 Fasteners - Marking and packaging.

GB/T 196 General purpose metric screw threads - Basic dimensions; GB/T 197 General purpose metric screw threads - Tolerances.

GB/T 1237 Designation method of fasteners.

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

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

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

GB/T 16938 Fasteners - Bolts, screws, studs and nuts - General requirements.

3 Dimensions

The form and the dimensions are given in Figure 1 and Table 1. The dimensional symbols and the method of indication conform to GB/T 5276.

Figure 1 shows the bolt with its countersunk head at an included angle of 75 degrees plus or minus 3 degrees, the square neck below the head, the plain shank and the threaded portion. The diameter of the unthreaded part of the shank is approximately equal to the pitch diameter or the major diameter of the thread. The end of the bolt is a rolled end in accordance with GB/T 2, and the head may be rounded or flat.

Table 1 gives, for each thread size from M6 to M20, the head diameter, the square neck width and depth, the head height, the thread length and the general range of nominal lengths.

4 Technical conditions and reference standards

The technical conditions and the reference standards are given in Table 2.

Table 2 fixes the material as steel and refers the general technical conditions to GB/T 16938; the thread tolerance and its standards to GB/T 196 and GB/T 197; the mechanical property classes and their standard to GB/T 3098.1; the product grade, which is grade C except as specified in Clause 3, and its tolerance standard to GB/T 3103.1; and the acceptance and packaging to GB/T 90.1 and GB/T 90.2. As to surface finish, the bolt may be supplied without treatment or oxidised, and any other surface treatment is a matter of agreement between supplier and purchaser.