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Mechanical Properties of Carbon Steel and Alloy Steel Coupling Components (Excerpt from JIS B 1051 2014)

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Bolts, Machine Screws, and Stud Bolts with Strength Classifications Stipulated – Coarse Screws

Mechanical or physical properties Strength classification
3.6 4.6 4.8 5.6 5.8 6.8 8.8 9.8*2 10.9 12.9
d≦16*1 d>16*1
Tensile strength　Rm　MPa *3 *4
[N/mm 2]		 Nominal dia.（c） 300 400   500   600 800 800 900 1,000 1,200
Min. 330 400 420 500 520 600 800 830 900 1,040 1,220
Hardness Vickers hardness
HV 		Min. 95 120 130 155 160 190 250 255 290 320 385
Max. 220*5 250 320 335 360 380 435
Brinell hardness
HB 		Min. 90 114 124 147 152 181 238 242 276 304 366
Max. 209*5 238 304 318 342 361 414
Rockwell hardness HRB Min. 52 67 71 79 82 89 - - - - -
Max. 95.0*5 99.5 - - - - -
HRC Min. - - - - - - 22 23 28 32 39
Max. - 32 34 37 39 44
Surface hardness　HV0.3 Max. - ＊6
Lower yield stress　ReL＊7
[N/mm 2]		 Nominal dia.（c） 180 240 320 300 400 480 -
Min. 190 240 340 300 420 480 -
0.2% yield strength　Rp0.2＊8
[N/mm 2]		 Nominal dia.（c） - 640 640 720 900 1,080
Min. - 640 660 720 940 1,100
Guaranteed load stress　 Guaranteed load stress ratio 0.94 0.94 0.91 0.93 0.90 0.92 0.91 0.91 0.90 0.88 0.88
[N/mm2] 180 225 310 280 380 440 580 600 650 830 970
Breaking elongation of mechanically worked test piece A　％ Min. 25 22 - 20 - - 12 12 10 9 8
Head hitting strength Shall not be destroyed
Height of the thread's non-decarbonized part　E Min. - 1/2H1 2/3H1 3/4H1
Depth of completely decarburized layer of screw thread　G ［mm］ Max. - 0.015

(a) Does not apply to steel structural bolts.
(b) Steel structural bolts are d ≧ M12.
(c) Nominal values are used only for the purpose of expressing strength classifications.
(d) Where the lower yield point ReL cannot be found, specification is according to 0.2% yield strength Rp0.2.
(e) Rpf min values for strength classifications 4.8, 5.8, and 6.8 are under research. Presented values are given only for calculating guaranteed load stress ratios, and are not values derived from testing.
(f) Guaranteed load test strength is stipulated separately.
(g) Hardness found for the tip of the screw on male-screw components is equal to or lower than 250HV, 238HB, or 99.5HRB.
(h) Where both surface hardness and base metal hardness are being sought at HV0.3, the surface hardness must not be harder than the measured screw base metal hardness by more than 30 points on the Vickers scale.
(i) Values found at test temperature of − 20°C.
(j) Applies to d ≧ 16 mm.
(k) Value for Kv is under research.
(l) Where agreed between supplying and receiving parties, JIS B 1043 may be applied instead of JIS B 1041.

Screw pitch P 0.5 0.6 0.7 0.8 1 1.25 1.5 1.75 2 2.5 3 3.5 4
H1 0.307 0.368 0.429 0.491 0.613 0.767 0.920 1.074 1.227 1.534 1.840 2.147 2.454
E
(Min.)		 Strength classification 8.8,9.8 0.154 0.184 0.215 0.245 0.307 0.384 0.460 0.537 0.614 0.767 0.920 1.074 1.227
10.9 0.205 0.245 0.286 0.327 0.409 0.511 0.613 0.716 0.818 1.023 1.227 1.431 1.636
12.9 0.230 0.276 0.322 0.368 0.460 0.575 0.690 0.806 0.920 1.151 1.380 1.610 1.841

Mechanical Properties and Maximum Tightening Torque of Hexagon Socket Head Cap Screw (in Case of Strength Classification 10.9 and 12.9 Coarse Screw Threads)

Reference
Nominal dia.（c） d Effective crosssectional area
［mm 2］		 Min. tensile load
［N］ 		Yield load
［N］ 		Guaranteed load
［N］ 		Max. allowable shaft force F
［N］ 		（Tf max.) Max. tightening torque［N・m］
K=0.17 K=0.25
10.9 12.9 10.9 12.9 10.9 12.9 10.9 12.9 10.9 12.9 10.9 12.9
M1.6 1.27 1,320 1,550 1,190 1,390 1,050 1,230 832 976 0.23 0.27 0.33 0.39
M2 2.07 2,150 2,530 1,940 2,270 1,720 2,010 1,360 1,590 0.46 0.54 0.68 0.80
M2.5 3.39 3,530 4,140 3,170 3,720 2,810 3,290 2,220 2,610 0.94 1.11 1.39 1.63
M3 5.03 5,230 6,140 4,710 5,520 4,180 4,880 3,300 3,870 1.68 1.97 2.47 2.90
M4 8.78 9,130 10,700 8,220 9,640 7,290 8,520 5,750 6,750 3.91 4.59 5.75 6.75
M5 14.2 14,800 17,300 13,300 15,600 11,800 13,800 9,300 10,900 7.91 9.28 11.6 13.6
M6 20.1 20,900 24,500 18,800 22,100 16,700 19,500 13,200 15,400 13.4 15.8 19.8 23.2
M8 36.6 38,100 44,600 34,300 40,200 30,400 35,500 24,000 28,100 32.6 38.3 48 56.3
M10 58.0 60,300 70,800 54,300 63,700 48,100 56,300 38,000 44,600 64.6 75.8 95 111
M12 84.3 87,700 103,000 78,900 92,600 70,000 81,800 55,200 64,800 113 132 166 194
M14 115 120,000 140,000 108,000 126,000 95,500 112,000 75,300 88,400 179 210 264 309
M16 157 163,000 192,000 147,000 172,000 130,000 152,000 103,000 121,000 280 328 411 483
M18 192 200,000 234,000 180,000 211,000 159,000 186,000 126,000 148,000 385 452 566 664
M20 245 255,000 299,000 229,000 269,000 203,000 238,000 161,000 188,000 546 640 803 942
M22 303 315,000 370,000 284,000 333,000 252,000 294,000 199,000 233,000 742 871 1,090 1,280
M24 353 367,000 431,000 330,000 388,000 293,000 342,000 231,000 271,000 944 1,110 1,390 1,630
M27 459 477,000 560,000 430,000 504,000 381,000 445,000 301,000 353,000 1,380 1,620 2,030 2,380
M30 561 583,000 684,000 525,000 616,000 466,000 544,000 368,000 431,000 1,870 2,200 2,760 3,230

K: Torque coefficient

Remark

  • 1. The minimum tensile load and the guaranteed load in the table above are based on JIS B 1051-2000.
  • 2. Yield load = yield strength (lower yield stress) x effective cross-sectional area
  • 3. Max. allowable shaft force ≒ 0.7 x yield load, and max. tightening torque (Tfmax) = torque coefficient (K) x max. allowable shaft force (F) x nominal diameter (d).
  • 4. In the case of torque coefficient K=0.17, oil lubrication, tightened material SS400, tightened surface finishing about 25S, female screw material SS400, and female screw accuracy 6 g or class 2 In the case of K=0.25, electrogalvanizing, tightened material SS400, tightened surface finishing about 25S, female screw material SCM, and female screw accuracy 6 g or class 2 Reference: If the female screw material is SS400 above, K=0.35.

Recommended Tightening Torque [Tf]

The recommended tightening torque (Tf) varies because the initial tightening force varies depending on the tool you use.
Recommended tightening torque (Tf) = tool-specific value x max. tightening torque (Tfmax)

Tool-specific value
  • 1）Manual tightening ： 0.65　Tfmax.
  • 2）Impact driver or powered driver ： 0.75　Tfmax.
  • 3）Torque wrench or torque limiting wrench ： 0.85　Tfmax.
  • 4）Torque wrench ： 0.9　 Tfmax.
Note: The above are reference values. Obtain the appropriate tightening torque based on the JIS B 1083 and 1084.

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