1. Scope and Field of Application : Covers the requirements for large series hexagon, high strength structural steel bolts in property classes 8.8 and 10.9 and in the size range M 16 to M36 with short thread lengths suitable for use in both friction-type and bearing-type structural steel joints. Bolts to this standard when matched with the appropriate nuts have been designed to provide an assembly with a high level of assurance against failure by thread stripping on over tightening.
2. Dimensions and Tolerances :
Attention is drawn to the importance of ensuring that the bolts are correctly used if satisfactory results are to be obtained.
2.1 The dimensions of the bolts shall be as given in Table 1.
2.2 The recommended length-size combinations shall be as given in Table 2.
2.3 Threads shall conform to tolerance class 6g of IS : 4218 (Part 6)-1978 ‘ISO metric screw threads: Part 6 Limits of sizes for commercial bolts and nuts (diameter range 1 to 52 mm) ( first revision )’. In case of hot-dip galvanized bolts, the specified tolerance class shall apply before hot-dip galvanizing.
3. Grade : Unless otherwise specified, the bolts shall be of product grade C as specified in IS : 1367 (Part 2)-1979 ‘Technical supply conditions for threaded steel fasteners: Part 2 Product grades and tolerances ( second revision )’.
4. Mechanical Properties :
The bolts shall be of property class 8.8 or 10.9 as specified in IS : 1367 (Part 3)-1979 ‘Technical supply conditions for threaded steel fasteners: Part 3 Mechanical properties and test methods for bolts, screws and studs with full load ability ( second revision )’.
4.1 For tensile, proof load and wedge loading test on full size bolts only four threads shall be exposed between the grips. This is obtained by freely running the nut or fixture to the fullest extent and then unscrewing the specimen four full turns.
4.2 For test purposes, the screw threads on hot-dip galvanized bolts shall be chemically stripped to permit assembly with a standard threaded grip or nut, that is, thread class 6H.
5. Finish :
5.1 Unless specified otherwise, the bolts shall be supplied in the dull black heat-treated condition with a residual coating of light oil.
5.2 Where property class 8.8 bolts are required to be hot-dip galvanized, they shall be galvanized in accordance with the requirements of IS : 1367 (Part 13)-1983 ‘Technical supply conditions for threaded steel fasteners: Part 13 Hot-dip galvanized coatings on threaded fasteners ( second revision )’. For fasteners with hot-dip galvanized coatings, the bolts or the mating nuts shall be provided with a suitable lubricant which shall be clean and dry to the touch to ensure that seizure shall not take place in assembly. The hot-dip galvanized bolts shall be subjected to the anti-seizing test as specified in Appendix A.
Note : Bolts of property class 10.9 should not be hot-dip galvanized since this may cause hydrogen embrittlement.
6. General Requirements :
6.1 In regard to permissible surface discontinuities, the bolts shall conform to IS : 1367 (Part 9)-1979 ‘Technical supply conditions for threaded steel fasteners: Part 9 Surface discontinuities on bolts, screws and studs ( second revision )’.
6.2 In regard to requirements not covered in the standard, the bolts shall conform to IS : 1367 (Part 1)-1980 ‘Technical supply conditions for threaded steel fasteners: Part 1 Introduction and general information ( second revision )’.
6.3 The high strength structural nuts to be used with these bolts shall conform to the requirements of IS : 6623-1985 ‘High strength structural nuts ( first revision )’.
6.3.1 These nuts shall be of the property class and finish for each type of bolt as follows:

6.4 Hardened and tempered washers to be used with these bolts shall conform to the requirements of IS : 6649-1985 ‘Hardened and tempered washers for high strength structural bolts and nuts ( first revision )’.
7. High strength structural bolts shall be designated by name, size, nominal length, the number of this standard and the property class identification symbol 8.8S or 10.9S—the suffix letter S denotes a high strength structural bolt with a large series hexagon head. In case of hot dip galvanized bolts, the word ‘galvanized’ shall be added to the designation. Example:
A high strength structural bolt of size M24, length 140 mm, property class 8.8 and galvanized shall be designated as:
High Strength Structural Bolt M24 × 140 IS : 3757—8.8S galvanized
7.1 If the bolt in the above example is required with a hot-dip galvanized high strength structural nut ( see IS : 6623-1985 ), the letter N shall be added to the designation as follows:
High Strength Structural Bolt M24 × 140 N IS : 3757—8.8S galvanized
8. Sampling : Sampling and criteria of acceptance shall be in accordance with IS : 2614-1969 ‘Methods for sampling of fasteners ( first revision )’.