GB/T 6188-2008 in English

《GB/T 6188-2008螺栓和螺钉用内六角花形》由TC85（全国紧固件标准化技术委员会）归口，主管部门为中国机械工业联合会。
本标准代替GB/T 6188-2000《螺栓和螺钉用内六角花形》。 本标准规定了螺栓和螺钉用内六角花形的型式与基本尺寸以及测量方法。
本标准与GB/T 6188-2000相比主要变化如下：
――调整了f的数值（见表2）；
――给出B、ri和re与A尺寸的近似关系式（见图A.1）.

Scope

This standard specifies the types and basic dimensions of hexagonal sockets for bolts and screws and the method of measurement. The curvature of the hexagonal socket curve for bolts and screws is determined by a gauge, which shall comply with the provisions of Tables 3 and 5. When drawing the profile curve, reference materials are given in Appendix A. For checking the hexagonal socket, this standard provides a detailed drawing, but the drawing should not be used as a standard for manufacturing. The types and basic dimensions of the hexagonal socket of this size are shown in Figure 1 and Table 1. The relevant countersunk hole specifications are as follows:
　——Countersunk hole diameter 0.13 mm, suitable for thread number Nq 15;
　——Countersunk hole diameter 0.25 mm, suitable for thread number Nq 15. The insertion depth should comply with the corresponding standards. ** Figure 1 Basic dimensions ** GB/T 6188-2008 / ISO 10664:2005 All measurements should be based on the top surface of the head. For semi-countersunk heads or round heads, the measurement should be based on the actual intersection of the top surface of the head and the hexagonal socket countersunk hole. When using a depth gauge, after the measuring head is pressed against the plane (the compression pointer rotates) to make it flush with the reference surface, adjust the gauge to the "O" position, see Figure 2. **Figure 2 Traceability gauge (O position)** 3.2 **Go gauge** The go gauge dimensions (see Figure 3) shall be within the limit dimensions specified in Table 3:
　——Maximum fillet dimension: 0.76 mm, applicable to thread number Nq 10;
　——Maximum fillet dimension: 0.254 mm, applicable to thread number Nq 10. **Figure 3 Go gauge dimensions** GB/T 6188-2008 / ISO 10664:2005 This standard is equivalent to ISO 10664:2005 "Hexagonal wrench for bolts and screws" (English version). This standard replaces GB/T 6188-2000 "Hexagonal wrench for bolts and screws". The main changes of this standard compared with GB/T 6188-2000 are as follows:
　——The numerical values of the dimensions are adjusted (see Table 2);
　——Bm and r are given (the approximate relationship between them and the A dimension, see Figure A). Appendix A of this standard is an informative appendix. This standard is proposed by the China Machinery Industry Federation and the responsible unit is the National Technical Committee for Standardization of Fasteners (SAC/TC85). The responsible drafting unit of this standard is the China Machinery Productivity Promotion Center, and the participating drafting unit is Dongguan Guoling Machinery Co., Ltd. The Secretariat of the National Technical Committee for Standardization of Fasteners is responsible for the interpretation of this standard. The previous versions of the standards replaced by this standard are:
　——GB6188-86 - GB/T 6188-2000 - GB/T 6188-2008 / ISO 10664:2005 **Table 5 Cylindrical no-stop gauge diameter dimensions (unit: mm)** | Screw No. | Cylindrical no-stop gauge diameter dimensions| |--------|------------------| | B No. | min | max | | 6 | 1.440 | 1.445 | | 8 | 1.920 | 1.925 | | 10 | 2.280 | 2.285 | | 15 | 2.760 | 2.765 | | 20 | 3.280 | 3.285 | | ... | ... | ... |