Why Use Wedge-Locking Instead of Friction-Based Locking?

What is the difference between friction-based locking and wedge locking, and when is lubrication needed?

The principle of friction locking is based on increased friction in the thread or under the bolt head/nut. The main disadvantage of this method is increased torsion stress in the joint. High torsion may cause the fastener to yield at a lower preload than expected. Since friction conditions are uneven you may not reach the necessary preload. Insufficient preload is the most common cause of the bolt’s failure, often due to fatigue. Lubricants are often used to minimize friction and to obtain uniform clamp load. However, lubrication will significantly reduce or even discharge locking ability of any friction-based method. Friction-based locking results in little or no control over achieved clamp load.

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The wedge locking method is based on tension instead of friction. The most common example of the wedge locking system is a pair of washers that have cams with a rise greater than the thread pitch of the bolt. The washer pair is installed cam face to cam face. When the bolt/nut is tightened teeth grip and lock the mating surfaces, allowing movement only across the cam faces. Any rotation of the bolt/nut is blocked by the wedge effect of the cams. The wedge locking ability is not affected by lubrication; furthermore, by using it, you can utilize each bolt to its full capacity.

HSFG / Structure Bolts- IS 3757 | ISO 7412

HSFG stands for High Strength Friction Grip where a traditional bolt will stop the plates in a connection from moving apart by supporting the weight on the bolt shank in the form of shear stress, an HSFG supports the weight by clamping the plates so tightly together that they can’t slip past each other.

The main advantages of HSFG bolted connections are their greater stiffness and their ability to withstand alternating forces. Their behavior under fatigue loading is also better than that of bearing bolted connections. Against these advantages are the costs of HSFG bolted connections.
The bolts are tightened to a shank tension so that the transverse load across the joint is resisted by the friction between the plated rather than the bolt shank's shear strength. We don’t use HSFG bolts often because they’re expensive and in most cases, they aren’t needed.
In other words, the friction generated between the plates is equal to the force being put on the plate by the weight of the beam it supports.
HSFG bolts are also commonly used in structures that will be exposed to a lot of vibrations, or loadings that will reverse. To make sure that the plates don’t slip past each other, the bolt needs to be carefully preloaded. The area around the bolt needs to be clean and unpainted and the bolt then needs to be tightened to a precise level.
In general,
HSFG  bolts are high-strength structural bolts that have been tightened such as to induce predefined tension in the bolt shank. They also will prevent any slip between the plates, which means your fastener won’t come loose.

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Annexure - I  -  Specifications - Table 1

Dia M16x2 M20x2.5 M22x2.5 M24x3 s 15.30 - 16.70 19.16 - 20.84 21.16 - 22.84 23.16 - 24.84 d 26.16 - 27.00 33.00 - 34.00 35.00 - 36.00 40.00 - 41.00 h 9.25 - 10.75 11.60 - 13.40 13.10 - 14.90 14.10 - 15.90 t < 100 31 36 38 41 l > 100 38 43 45 48 Proof Load in N  8.8S 91060 147000 181800 211800 10.9S 130310 203350 251490 292990 Mechanical Property: 8.8 or 10.9 as per ISO 898, IS 1367 (3) Threads: ISO Metric 6g Class as per ISO 965, IS 4218

Dia M27x3 M30x3.5 M36x4 s 26.16 - 27.84 29.16 - 30.84 35.00 - 37.00 d 45.00 - 46.00 49.00 - 50.00 58.80 - 60.00 h 16.10 - 17.90 17.65 - 19.75 21.45 - 23.55 t < 100 44 49 56 l > 100 51 56 63 Proof Load in N  8.8S 275400 336600 490200 10.9S 380970 465630 678110

Annexure-II  -  Selection Chart for Bolt Length & Weight  (kg./1000 pcs.) - Table 2

Dia M16 M20 M22 M24 Length Grip Length Weight Grip Length Weight Grip Length Weight Grip Length Weight 40mm   10 to 14 102.8             45mm   15 to 19 110.7 11 to 15 180.3         50mm   20 to 24 118.6 16 to 20 192.6 12 to 16 252.0     55mm   25 to 29 126.5 21 to 25 205.0 17 to 21 266.9 15 to 19 337.4 60mm   30 to 34 134.4 26 to 30 217.3 22 to 26 281.8 20 to 24 355.2 65mm   35 to 39 142.3 31 to 35 229.6 27 to 31 296.7 25 to 29 372.9 70mm   40 to 44 150.2 36 to 40 241.9 32 to 36 311.6 30 to 34 390.7 75mm   45 to 49 158.1 41 to 45 254.3 37 to 41 326.6 35 to 39 408.4 80mm   50 to 54 166.0 46 to 50 266.6 42 to 46 341.5 40 to 44 426.2 85mm   55 to 59 173.9 51 to 55 278.9 47 to 51 356.4 45 to 49 443.9 90mm   60 to 64 181.7 56 to 60 291.3 52 to 56 371.3 50 to 54 461.7 95mm   65 to 69 189.6 61 to 65 303.6 56 to 61 386.2 55 to 59 479.4 100mm   70 to 74 197.5 66 to 70 315.9 62 to 66 401.2 60 to 64 497.2 110mm   75 to 84 211.4 71 to 80 337.7 67 to 76 427.8 65 to 74 528.5 120mm   85 to 94 227.2 81 to 90 362.4 77 to 86 457.7 75 to 84 564.1 130mm   95 to 104 243.0 91 to 100 387.0 87 to 96 487.5 85 to 94 599.6 140mm   105 to 114 258.8 101 to 110 411.7 97 to 106 517.3 95 to 104 635.1 150mm   115 to 124 274.6 111 to 120 436.3 107 to 116 547.2 105 to 14 670.6 160mm   125 to 134 290.3 121 to 130 461.0 117 to 126 577.0 115 to 124 706.1 170mm   135 to 144 306.1 131 to 140 485.7 127 to 136 606.9 125 to 134 741.6 180mm   145 to 154 321.9 141 to 150 510.3 137 to 146 636.7 135 to 144 777.1 190mm   155 to 164 337.7 151 to 160 535.0 147 to 156 666.5 145 to 154 812.6 200mm   165 to 174 353.5 161 to 170 559.6 157 to 166 694.4 155 to 164 848.2 210mm                   220mm                   230mm                   240mm                   250mm                  

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Dia M27 M30 M36 Length Grip Length Weight Grip Length Weight Grip Length Weight 40mm                45mm               50mm               55mm               60mm   17 to 21 480.9         65mm   22 to 26 503.4         70mm   27 to 31 525.8 24 to 28 672.5     75mm   32 to 36 548.3 29 to 33 700.3 23 to 27 1089.1 80mm   37 to 41 570.8 34 to 38 728.0 28 to 32 1129.0 85mm   42 to 46 593.2 39 to 3 755.7 33 to 37 1169.0 90mm   47 to 51 615.7 44 to 48 783.5 38 to 42 1209.0 95mm   52 to 56 638.2 49 to 53 811.2 43 to 47 1248.9 100mm   57 to 61 660.7 54 to 58 839.0 48 to 52 1288.9 110mm   62 to 71 685.6 59 to 68 888.4 53 to 2 1362.0 120mm   72 to 81 730.6 69 to 78 943.9 63 to 72 1441.9 130mm   82 to 91 775.5 79 to 88 999.4 73 to 82 1521.8 140mm   92 to 101 820.5 89 to 98 1054.9 83 to 92 1601.7 150mm   102 to 111 865.4 99 to 108 1110.4 93 to 102 1681.6 160mm   112 to 121 910.4 109 to 118 1165.8 103 to 112 1761.5 170mm   122 to 131 955.3 119 to 128 1221.3 113 to 122 1841.4 180mm   132 to 141 1000.2 129 to 138 1276.8 123 to 132 1921.3 190mm   142 to 151 1045.2 139 to 148 1332.3 133 to 142 2001.2 200mm   152 to 161 1090.2 149 to 158 1387.8 143 to 152 2081.1 210mm   162 to 171 1135.2 159 to 168 1443.3 153 to 162 2161.0 220mm   172 to 181 1180.1 169 to 178 1498.8 163 to 172 2240.9 230mm   182 to 191 1225.0 179 to 188 1554.3 173 to 182 2320.8 240mm   192 to 201 1270.0 189 to 198 1609.8 183 to 192 2400.7 250mm   202 to 211 1314.0 199 to 208 1665.3 193 to 202 2480.6 260mm   212 to 221 1359.9 209 to 218 1720.7 203 to 212 2560.5 270mm   222 to 231 1404.9 219 to 228 1776.2 213 to 222 2640.4 280mm   232 to 241 1449.8 229 to 238 1831.7 223 to 232 2720.3 290mm   242 to 251 1493.9 239 to 248 1887.2 233 to 242 2800.2 300mm   252 to 261 1538.9 249 to 258 1942.7 243 to 252 2880.1