Proof Loads for Nuts


ISO Metric (Coarse) Threads ISO 898-2 (Recommended)

Thread
D 		Pitch
P 		Proof load a, N
Property class
04 05 5 6 8 9 10 12
M5 0,8 5400 7100 8250 9500 12140 13000 14800 16300
M6 1 7640 10000 11700 13500 17200 18400 20900 23100
M7 1 11000 14500 16800 19400 24700 26400 30100 33200
M8 1,25 13900 18300 21600 24900 31800 34400 38100 42500
M10 1,5 22000 29000 34200 39400 50500 54500 60300 67300
M12 1,75 32000 42200 51400 59000 74200 80100 88500 100300
M14 2 43700 57500 70200 80500 101200 109300 120800 136900
M16 2 59700 78500 95800 109900 138200 149200 164900 186800
M18 2,5 73000 96000 121000 138200 176600 176600 203500 230400
M20 2,5 93100 122500 154400 176400 225400 225400 259700 294000
M22 2,5 115100 151500 190900 218200 278800 278800 321200 363600
M24 3 134100 176500 222400 254200 324800 324800 374200 423600
M27 3 174400 229500 289200 330500 422300 422300 486500 550800
M30 3,5 213200 280500 353400 403900 516100 516100 594700 673200
M33 3,5 263700 347000 437200 499700 638500 638500 735600 832800
M36 4 310500 408500 514700 588200 751600 751600 866000 980400
M39 4 370900 488000 614900 702700 897900 897900 1035000 1171000
a For the application of thin nuts, it should be considered that the stripping load is lower than the proof load of a nut with full loadability.


Proof Loads for Nuts


ISO Metric (Fine) Threads ISO 898-2 (Hardness Properties for Nuts)

Thread
D × P 		Proof load a, N
Property class
04 05 5 6 8 10 12
M8 × 1 14900 19600 27000 30200 37400 43100 47000
M10 × 1,25 23300 30600 44200 47100 58400 67300 73400
M10 × 1 24500 32200 44500 49700 61600 71000 77400
M12 × 1,5 33500 44000 60800 68700 84100 97800 105700
M12 × 1,25 35000 46000 63500 71800 88000 102200 110500
M14 × 1,5 47500 62500 86300 97500 119400 138800 150000
M16 × 1,5 63500 83500 115200 130300 159500 185400 200400
M18 × 2 77500 102000 146900 177500 210100 220300 —
M18×1,5 81 700 107 500 154 800 187 000 221 500 232 200 —
M20 × 2 98000 129000 185800 224500 265700 278600 —
M20 × 1,5 103400 136000 195800 236600 280200 293800 —
M22 × 2 120800 159000 229000 276700 327500 343400 —
M22 × 1,5 126500 166500 239800 289700 343000 359600 —
M24 × 2 145900 192000 276500 334100 395500 414700 —
M27 × 2 188500 248000 351100 431500 510900 535700 —
M30 × 2 236000 310500 447100 540300 639600 670700 —
M33 × 2 289200 380500 547900 662100 783800 821900 —
M36 × 3 328700 432500 622800 804400 942800 934200 —
M39 × 3 391400 515000 741600 957900 1123000 1112000 —
a For the application of thin nuts, it should be considered that the stripping load is lower than the proof load of a nut with full loadability.


Proof Loads for Fasteners


ISO Metric (Coarse) Threads ISO 898/I-1988

Nominal Diameter Of Thread d(mm) Pitch P(mm) Nomincal Stress Area As (mm2) Property Class
3.6 4.6 4.8 5.6 5.8 6.8 8.8 9.8 10.9 12.9
Proof Load (As . Ap),N
3 0.50 5.03 910 1130 1560 1410 1910 2210 2920 3270 4180 4880
3.5 0.60 6.78 1220 1530 2100 1900 2580 2980 3940 4410 5630 6580
4 0.70 8.78 1580 1980 2770 2460 3340 3860 5100 5710 7290 8520
5 0.80 14.20 2560 3200 4400 3980 5400 6250 8230 9230 11800 13800
6 1.00 20.10 3620 4520 6230 5630 7640 8840 11600 13100 16700 19500
7 1.00 28.90 5200 6500 8920 8090 11000 12700 16800 18800 24000 28000
8 1.25 36.60 6590 8240 11400 10200 13900 16100 21200 23800 30400 35500
10 1.50 58.00 10400 13000 18000 16200 22000 25500 33700 37700 48100 56300
12 1.75 84.30 15200 19000 26100 23600 32000 37100 489001) 54800 70000 81800
14 2.00 115 20700 25900 35600 32200 43700 50600 667001) 74800 95500 112000
16 2.00 157 28300 35300 48700 44000 59700 69100 910001) 102000 130000 152000
18 2.50 192 34600 43200 59500 53800 73000 84500 11500 159000 186000
20 2.50 245 44100 55100 76000 68600 93100 108000 147000 203000 238000
22 2.50 303 54500 68200 93900 84800 115000 133000 182000 252000 294000
24 3.00 353 63500 79400 109000 98800 134000 155000 212000 293000 342000
27 3.00 459 82600 103000 142000 128000 174000 202000 275000 381000 445000
30 3.50 561 101000 126000 174000 157000 213000 247000 337000 466000 544000
33 3.50 694 125000 156000 215000 194000 264000 305000 416000 570000 673000
36 4.00 817 147000 184000 253000 229000 310000 359000 490000 678000 792000
39 4.00 976 176000 220000 303000 273000 371000 429000 586000 810000 947000
1)For structural steel screws 50700,68800 and 94500 N


Proof Loads For Screws


ISO Metric (Fine) Threads ISO 898/I-1988

Nominal Diameter Of Thread d(mm) Pitch P(mm) Nomincal Stress Area As (mm2) Property Class
3.6 4.6 4.8 5.6 5.8 6.8 8.8 9.8 10.9 12.9
Proof Load (As . Ap),N
8 1.00 39.2 7060 8820 12200 11000 14900 17200 22700 25500 32500 38000
10 1.25 61.2 11000 13800 19000 17100 23300 26900 33500 39800 50800 59400
12 1.25 92.1 16600 20700 28600 25800 35000 40500 53400 59900 76300 89300
14 1.50 125 22500 28100 38800 35000 47500 55000 72500 81200 104000 121000
16 1.50 167 30100 27600 51800 46800 63500 73500 96900 109000 139000 162000
18 1.50 216 38900 48600 67000 60500 82100 95000 130000 179000 210000
20 1.50 272 49000 61200 84300 76200 103000 120000 163000 226000 264000
22 1.50 333 59900 74900 103000 93200 126000 146000 200000 276000 323000
24 2.00 384 69100 86400 119000 108000 146000 169000 230000 319000 372000
27 2.00 496 89300 112000 154000 139000 188000 218000 298000 412000 481000
30 2.00 621 112000 140000 192000 171000 236000 273000 373000 515000 602000
33 2.00 761 137000 171000 236000 213000 289000 335000 457000 632000 738000
36 3.00 865 156000 195000 268000 242000 329000 381000 519000 718000 838000
39 3.00 1030 185000 232000 319000 288000 391000 453000 618000 855000 999000


Proof Loads For Nuts (Coarse Thread)


According to DIN 934 and DIN 985 (Ref. DIN 267/4)

Thread Size Pitch P(mm) Nominal Stress Area of Test Mandrel As mm2 Property Class
4 5 6 8 10 12
Proof Load (As * Sp), in N
M3  0.50 5.03 2500 3000 4000 5000 6000
M3.5  0.60 6.78 3400 4050 5400 6800 8150
M4  0.70 8.78 4400 5250 7000 8750 10500
M5  0.80 14.2 7100 8500 11400 11400 17000
M6  1.00 20.1 10000 12000 16000 20000 24000
M7  1.00 28.9 14500 17300 23000 29000 34700
M8  1.25 36.6 18300 22000 29000 36500 43000
M10  1.50 58.0 29000 35000 46000 58000 69500
M12 1.75 84.5 42100 50500 67000 84000 100000
M14  2.00 115 57500 69000 92000 115000 138000
M16  2.00 157 78500 94000 126000 157000 188000
M18  2.50 192 76800 96000 115000 154000 192000 230000
M20  2.50 245 98000 122000 147000 196000 245000 294000
M22  2.50 303 121000 151000 182000 242000 303000 364000
M24  3.00 353 141000 176000 212000 282000 353000 423000
M27  3.00 459 184000 230000 276000 367000 459000 550000
M30  3.50 561 224000 280000 336000 448000 561000 673000
M33  3.50 694 277000 347000 416000 555000 694000 833000
M36  4.00 817 327000 408000 490000 653000 817000 980000
M39  4.00 976 390000 488000 585000 780000 976000 1170000
The above proof loads are also valid for nuts where the property class marking is enclosed by two vertical lines |8|Conversion Factor: 1N = 0.2248 lb.


Proof Loads For Nuts (Fine Thread)


According to DIN 934 and DIN 985 (Ref. DIN 267/4)

Thread Size Pitch P(mm) Nominal Stress Area of Test Mandrel As mm2 Property Class
5 6 8 10 12
Proof Load (As * Sp), in N
M8 1.00 39.2 19600 23500 31000 39000 47000
M10 1.00 64.5 32200 38700 51500 64500 77500
M10 1.25 61.2 30600 37000 49000 61000 73500
M12 1.25 92.1 46000 55000 74000 92000 110000
M12 1.50 88.1 44000 53000 70000 88000 106000
M14 1.50 125 62200 75000 100000 125000 150000
M16 1.50 167 83500 100000 134000 167000 200000
M18 1.50 216 108000 129000 173000 216000 259000
M18 2.00 204 102000 122000 163000 204000 245000
M20 1.50 272 136000 163000 218000 272000 326000
M20 2.00 258 129000 155000 206000 258000 310000
M22 1.50 333 166000 200000 266000 333000 400000
M22 2.00 318 159000 191000 254000 318000 382000
M24 2.00 384 192000 230000 307000 384000 460000
M27 2.00 496 248000 298000 397000 496000 595000
M30 2.00 621 310000 373000 497000 621000 745000
M33 2.00 761 380000 456000 608000 761000 914000
M36 3.00 865 432000 519000 692000 865000 1040000
M39 3.00 1030 501000 618000 825000 1030000 1240000
The above proof loads are also valid for nuts where the property class marking is enclosed by two vertical lines |8| Conversion Factor: 1N = 0.2248 lb.


Most metric nuts are still purchased to the withdrawn DIN standard, you would expect that you will get the property class that you specified, however there is an important issue that you may need to consider.  DIN standard nuts can be made to the mechanical properties of DIN 267 part 4 or ISO 898-2, the problem is that the DIN standard does not meet the proof load and hardness required by the now active ISO standard.  To this day the manufacturers ask if you want the “Real” class or the cheaper DIN 267 parts.

What is the difference and why should I care?  The ISO specification has a slightly higher Proof Load and also require a minimum hardness to ensure the nut does not fail before the bolt/screw.

Per ISO….. An optimized bolted joint, consisting of a bolt, screw or stud of a given property class according to ISO 898-1 assembled with a regular or high nut of the mating property class according to this part of ISO 898 is able to provide a maximum preload, using the full strength of the bolt. In the case of over-tightening, the fracture occurs in the loaded threaded part of the bolt, which gives an obvious indication of a tightening failure.

DIN 267-4 has no minimum hardness requirement, a lower Proof Load and a requirement to mark the class with two vertical lines such as |8| for example.

Why should you care as both standards area valid?  Are the DIN 267-4 nuts going to fail, probably not however do you really want to take that risk.  A good QC departments could fail the parts and in case of a failure in the field it could be a big mess.  There is no good guidance from the standards associations in this regard, Carmen Vertullo from Carver Engineering has spent some time on this subject and there is more to come on this later.

Fuller has been purchasing the parts to the ISO 898-2 if at all possible as the minimal savings are simply not worth the risk, we rather make sure our parts meet both the DIN and ISO mechanical requirements.  You should be aware of what you need for your application and what you are purchasing from your suppliers.

More details for your reference can be found at our fullerfasteners.com site. DIN 934 Hex Nut

Proof Loads: https://fullerfasteners.com/tech/proof-loads-for-fasteners/
Mechanical: https://fullerfasteners.com/tech/mechanical-properties/

More to follow later……..