Untitled Document

Torque Required To Produce Bolt Stress

The torque required to produce a certain stress in bolting is dependent upon a number of conditions, including:

  1. Diameter of bolt
  2. Type and number of threads on bolt
  3. Material of bolt
  4. Condition of nut bearing surfaces
  5. Lubrication of bolt threads and nut bearing surfaces
The tables below reflect the results of many tests to determine the relation between torque and bolt stress. Values are based on steel bolts which have been well lubricated with a heavy graphite and oil mixture.

It has been found that a non-lubricated bolt has an efficiency of about 50 percent of a well lubricated bolt. Also, different lubricants produce results which vary from 50 to 100 percent of the tabulated stress fingers.
DATA FOR USE WITH ALLOW STEEL STUD BOLTS
LOAD IN POUNDS ON STUD BOLTS WHEN TORQUE LOADS ARE APPLIED
Nominal Diameter of Bolt (Inches) Number of Threads (Per Inch) Diameter at Root of Thread (Inches) Area at Root of Thread (Sq. Inch) Stress
30,000 PSI 45,000 PSI 60,000 PSI
Torque Ft. Lbs. Compression, Lbs. Torque Ft. Lbs. Compression, Lbs. Torque Ft. Lbs. Compression, Lbs.
1/4 20 185 027 4 810 6 1215
 8
 1620
5/16 18 240 045 8 1350 12 2025
 16
 2700
3/8 16 294 068 12 2040 18
 3060
 24
 4080
7/16 14 345 093 20 2790 30
 4185
 40
 5580
1/2 13 400 126 30 3780 45
 5670
 60
 7560
9/16 12 454 162 45 4860 68
 7290
 90
 9720
5/8 11 507 202 60 6060 90
 9090
 120
 12120
3/4 10 620 302 100 9060 150
 13590
 200
 18120
7/8 9 731 419 160 12570 240
 18855
 320
 25140
1 8 838 551 245 16530 368
 24795
 490
 33060
1-1/8 8 963 728 355 21840 533
 32760
 710
 43680
1-1/4 8 1088 929 500 27870 750
 41805
 1000
 55740
1-3/8 8 1213 1155 680 34650 1020
 51975
 1360
 69300
1-1/2 8 1338 1405 800 42150 1200
 63225
 1600
 84300
1-5/8 8 1463 1680 1100 50400 1650
 75600
 2200
 100800
1-3/4 8 1588 1980 1500 59400 2250
 89100
 3000
 118800
1-7/8 8 1713 2304 2000 69120 3000
 103680
 4000
 138240
2 8 1838 2652 2200 79560 3300
 119340 4400
 159120
2-1/4 8 2088 3423 3180 102690 4770
 154035
 6360
 205380
2-1/2 8 2338 4292 4400 128760 6600
 193140
 8800
 257520
2-3/4 8 2588 5259 5920 157770 8880
 236655
 11840
 325540
3 8 2838 5259 7720 189720 11580 284580 15440 379440
DATA FOR USE WITH MACHINE BOLTS AND COLD ROLLED STEEL STUD BOLTS
LOAD IN POUNDS ON BOLTS AND STUD BOLTS WHEN TORQUE LOADS ARE APPLIED
Nominal Diameter of Bolt (Inches) Number of Threads (Per Inch) Diameter at Root of Thread (Inches) Area at Root of Thread (Sq. Inch) Stress
7500 PSI 15,000 PSI 30,000 PSI
Torque Ft. Lbs. Compression, Lbs. Torque Ft. Lbs. Compression, Lbs. Torque Ft. Lbs. Compression, Lbs.
1/4
 20
 185
 027
 1
 203
 2
 405
 4
 810
5/16
 18
 240
 045
 2
 338
 4
 675
 8
 1350
3/8
 16
 294
 068
 3
 510
 6
 1020
 12
 2040
7/16
 14
 345
 093
 5
 698
 10
 1395
 20
 2790
1/2
 13
 400
 126
 8
 945
 15
 1890
 30
 3780
9/16
 12
 454
 162
 12
 1215
 23
 2430
 45
 4860
5/8
 11
 507
 202
 15
 1515
 30
 3030
 60
 6060
3/4
 10
 620
 302
 25
 2265
 50
 4530
 100
 9060
7/8
 9
 731
 419
 40
 3143
 80
 6285
 160
 12570
1
 8
 838
 551
 62
 4133
 123
 8265
 245
 16530
1-1/8
 7
 939
 693
 98
 5190
 195
 10380
 390
 20760
1-1/4
 7
 1064
 890
 137
 6675
 273
 13350
 545
 26700
1-3/8
 6
 1158
 1054
 183
 7905
 365
 15810
 730
 31620
1-1/2
 6
 1283
 1294
 219
 9705
 437
 19410
 875
 38820
1-5/8
 5-1/2
 1389
 1515
 300
 11363
 600
 22725
 1200
 45450
1-3/4
 5
 1490
 1744
 390
 13080
 775
 26160
 1550
 52320
1-7/8
 5
 1615
 2049
 525
 15368
 1050
 30735
 2100
 61470
2 4-1/2 1711 2300 563 17250 1125 34500 2250 69000