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3757 | Nut (Hardware) | Screw
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Sw10 Assembly Springmotionstudy
UDC 621.882.211 [669.14.018.291] (Reaffirmed 2003) Edition 3.2 (1989-07)
(Incorporating Amendment Nos. 1 & 2) 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 overtightening.
Note Attention is drawn to the importance of ensuring that the bolts are correctly used if satisfactory results are to be obtained.
Bolts, Nuts and Fastener Accessories Sectional Committee, EDC 27 [Ref : Doc EDC 27 (4286)]
2. Dimensions and Tolerances 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 loadability ( 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 ). Adopted 26 July 1985 BIS 2008 Price Group 3
TABLE 1 DIMENSIONS FOR HIGH STRENGTH STRUCTURAL BOLTS* ( Clause 2.1 ) All dimensions in millimetres.
Thread Size d p Pitch of thread
M16 2 31 38 0.8 0.4 18.7 16.70 15.30 24.9 29.56 10 10.75 9.25 6.5 0.6 27 26.16 3
M20 2.5 36 43 0.8 0.4 23.24 20.84 19.16 31.4 37.29 12.5 13.40 11.60 8.1 0.8 34 33 3.8
(M22) 2.5 38 45 0.8 0.4 25.24 22.84 21.16 33.3 39.55 14 14.90 13.10 9.2 0.8 36 35 3.8
M24 3 41 48 0.8 0.4 27.64 24.84 23.16 38.0 45.20 15 15.90 14.10 9.9 1.0 41 40 4.5
(M27) 3 44 51 0.8 0.4 31.24 27.84 26.16 42.8 50.85 17 17.90 16.10 11.3 1.2 46 45 4.5
M30 3.5 49 56 0.8 0.4 34.24 30.84 29.16 46.5 55.37 18.7 19.75 17.65 12.4 1.2 50 49 5.3
M36 4 56 63 0.8 0.4 41.00 37.00 35.00 55.9 66.44 22.5 23.55 21.45 15.0 1.5 60 58.8 6
100 bref For length/Nom ----------> 100
c da ds dw e k k' r s Chamfer length z Max Min Max Max Min Max Min Min Nom Max Min Min Min Max Min Max
Note Sizes shown in brackets are of second preference. *For hot-dip galvanized bolts, the above dimensions apply before galvanizing. dw, Max = s actual.
RECOMMENDED LENGTH-SIZE COMBINATIONS FOR HIGH STRENGTH STRUCTURAL BOLTS ( Clause 2.2 ) All dimensions in millimetres. M16 ls lg Max 9 14 19 24 29 34 39 44 49 54 59 64 69 72 82 92 102 112 122 132 142 152 162 172 182 192 202 212 222 232 242 252 262 ls Min 4 6.5 11.5 16.5 21.5 26.5 31.5 36.5 41.5 46.5 51.5 56.5 59.5 69.5 79.5 89.5 99.5 109.5 119.5 129.5 139.5 149.5 159.5 169.5 179.5 189.5 199.5 209.5 219.5 229.5 239.5 249.5 M20 lg Max 11.5 14 19 24 29 34 39 44 49 54 59 64 67 77 87 97 107 117 127 137 147 157 167 177 187 197 207 217 227 237 247 257 ls Min (M22) lg Max ls Min M24 lg Max ls Min (M27) lg Max ls Min M30 lg Max ls Min M36 lg Max
Thread Size d Length l Nom 40 45 50 55 60 65 70 75 80 85 90 95 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 Min 38.75 43.75 48.75 53.5 58.5 63.5 68.5 73.5 78.5 83.25 88.25 93.25 98.25 108.25 118.25 128 138 148 156 166 176 186 196 206 216 226 236 246 256 266 276 286 296 Max 41.25 46.25 51.25 56.5 61.5 66.5 71.5 76.5 81.5 86.75 91.75 96.75 101.75 111.75 121.75 132 142 152 164 174 184 194 204 214 224 234 244 254 264 274 284 294 304
Min 3 8 13 18 23 28 33 38 43 48 53 58 63 66 76 86 96 106 116 126 136 146 156 166 176 186 196 206 216 226 236 246 256
4 9.5 14.5 19.5 24.5 29.5 34.5 39.5 44.5 49.5 54.5 57.5 67.5 77.5 87.5 97.5 107.5 117.5 127.5 137.5 147.5 157.5 167.5 177.5 187.5 197.5 207.5 217.5 227.5 237.5 247.5
11.5 17 22 27 32 37 42 47 52 57 62 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215 225 235 245 255
5 10 15 20 25 30 35 40 45 50 53 63 73 83 93 103 113 123 133 143 153 163 173 183 193 203 213 223 233 243
14 19 24 29 34 39 44 49 54 59 62 72 82 92 102 112 122 132 142 152 162 172 182 192 202 212 222 232 242 252
5 12 17 22 27 32 37 42 47 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240
14 21 26 31 36 41 46 51 56 59 69 79 89 99 109 119 129 139 149 159 169 179 189 199 209 219 229 239 249
6 10.5 15.5 20.5 25.5 30.5 35.5 40.5 43.5 53.5 63.5 73.5 83.5 93.5 103.5 113.5 123.5 133.5 143.5 153.5 163.5 173.5 183.5 193.5 203.5 213.5 223.5 233.5
16.5 21 26 31 36 41 46 51 54 64 74 84 94 104 114 124 134 144 154 164 174 184 194 204 214 224 234 244
6 12 17 22 27 32 35 45 55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215 225
18 24 29 34 39 44 47 57 67 77 87 97 107 117 127 137 147 157 167 177 187 197 207 217 227 237
Note 1 Recommended lengths are below the bold stepped line. Note 2 Sizes shown in brackets are of second preference. Formulae: lg, Max = lnom bref ls, Min = lg, Max 3 P For bolts with lengths above the bold line, ls, Min ~ 1.5 and lg, Max = ls, Min + 3 P
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: Bolt Property Class and Finish 8.8S, dull black 8.8S, hot-dip galvanized 10.9S, dull black Nut Property Class and Finish 8S or 10S, dull black 10S, hot-dip galvanized 10S, dull black
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. Designation 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 10.9Sthe 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 : 37578.8S 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 : 37578.8S galvanized 8. Sampling Sampling and criteria of acceptance shall be in accordance with IS : 2614-1969 Methods for sampling of fasteners ( first revision ). 9. Marking High strength structural bolts shall be marked with the following symbols on the top surface of the bolt head, either embossed or indented, as shown below: a) The manufacturers identification symbol, and b) The property class identification symbol 8S for 8.8S or 10S for 10.9S. Minimum height of markings shall be 4.0 mm. When embossed, markings shall project not less than 0.3 mm above the surface of the head and total head height (head plus markings) shall not exceed the specified maximum head height plus 0.4 mm.
10. Mode of Delivery The bolts shall be delivered in accordance with IS : 1367 (Part 18)-1979 Technical supply conditions for threaded steel fasteners: Part 18 Marking and mode of delivery ( second revision ). 11. Certification Marking Details available with the Bureau of Indian Standards.
IS : 3757 - 1985 APPENDIX A
( Clause 5.2 ) ANTI-SEIZING TEST FOR HOT-DIP GALVANIZED FASTENERS A-1. Where bolts and the mating nuts and washers with hot-dip galvanized coating are specified, these shall be subject to the following anti-seizing test for testing the effectiveness of the lubricant coating applied to the hot-dip galvanized bolts or nuts: a) The test shall be carried out on bolts, nuts and washers in the condition as supplied by the manufacturer and shall be in accordance with, and include a lubricant coating as required by 5.2. There shall be no other lubricant applied for the purpose of this test. If the test is performed by the user it shall be carried out immediately after receipt of the bolts, nuts and washers from the manufacturer. b) The bolt with nut and washer selected for testing shall be placed with the washer directly under the nut in a steel joint with total thickness so that three to five full threads of the bolt are located between the bearing surfaces of the bolt head and nut. The diameter of the holes in the assembly shall have the same nominal diameter as the hole in the washer. c) The nut shall be initially tightened to produce a load in the bolt not less than 10 percent of the specified proof load. After this initial tightening, the bolt and the nut position shall be marked to provide the starting point for the rotational movement to be measured. During nut rotation the bolt head shall be restrained from turning, and the final tensioning shall be completed without stopping the motion of the nut. The nut shall be rotated in accordance with the requirements of Table 3 from the initial tightening position without fracture of the bolt, or stripping of the bolt or nut thread.
TABLE 3 Bolt Length (Nominal) / 2d < / 3d < / 4d < / 2d 3d 4d 8d / > 8d NUT ROTATION REQUIREMENTS Nut Rotation ( Min ) 180 240 300 360 420
IS : 3757 Specification for high tensile friction grip fasteners for structural engineering purposes was originally published in 1966. The first revision of IS : 3757 catered for high tensile friction grip bolts only; the corresponding nuts and washers were covered by separate standards. In the present revision of IS : 3757, the title of the standard has been changed to High strength structural bolts to enable them to be used for both friction-type and bearing type of structural steel connections with the same bolting installation procedure. Further, shorter thread lengths have been provided to ensure no thread protrusion in the shear plane so that higher working stresses can be adopted for bearing-type connections. Also due to technical reasons, the width across flats for M20 size has been changed from 32 to 34 mm in line with IS : 9519-1980 Width across flats for hexagon head bolts and nuts. It is, however, recognized that some transition period would be essential during which the new across flat size would be introduced and the old across 5
flat size phased out. During this transition period, the bolts may be supplied with the old across flat size and other related dimensions as mentioned below as being functionally equivalent. However, bolts with old across flat site should not be supplied with nuts with new across flat size and vice-versa. All dimensions in millimetres. Thread Size d s e dw Max Min Min Max Min M20 32 31 35.03 s actual 29.5
The standard is based on ISO/DIS 7412 High strength structural bolts (short thread length type) issued by the International Organization for Standardization. This edition 3.2 incorporates Amendment No. 1 (October 1987) and Amendment No. 2 (July 1989). Side bar indicates modification of the text as the result of incorporation of the amendments.
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