Torque Required to Produce Bolt Stress

[Pages:1]Torque Required to Produce Bolt Stress

The torque or turning effort required to produce a certain stress in bolting is dependent upon a number of conditions, some of which are: 1. Diameter of Bolt; 2. Type and number of threads on bolt; 3. Material of bolt; 4. Condition of nut bearing surfaces; and, 5. Lubrication of bolt threads and net bearing surfaces. The table below reflect the results of many tests to determine the relation between torque and bolt stress. Values are based on steel bolting well lubricated with a heavy graphite and oil mixture with a friction value of 0.177. It was found that a non-lubricated bolt has an efficiecy of about 50% of a well lubricated bolt and also that different lubricants produce results varying between the limits of 50 and 100% of the tabulated stress figures.

Torque Chart

Nominal Diameter of Stud (Inches)

1/4 5/16 3/8 7/16 1/2 9/16 5/8 3/4 7/8 1 1 1/8 1 1/4 1 3/8 1 1/2 1 5/8 1 3/4 1 7/8 2 2 1/4 2 1/2 2 3/4 3

Diameter at Root of Threads (Inches)

0.185 0.24 0.294 0.345 0.4 0.454 0.507 0.62 0.731 0.838 0.963 1.088 1.213 1.338 1.463 1.588 1.713 1.838 2.088 2.338 2.588 2.838

Area at Root of Threads (Sq. Inches)

0.027 0.045 0.068 0.093 0.126 0.162 0.202 0.302 0.419 0.551 0.728 0.929 1.155 1.405 1.68 1.98 2.304 2.652 3.423 4.292 5.259 6.324

30,000 PSI

Torque Ft. Lbs.

Compression Lbs.

4

810

8

1350

12

2040

20

2790

30

3780

45

4860

60

6060

100

9060

160

12570

245

16530

355

21840

500

27870

680

34650

800

42150

1100 1500 2000

50400 59400 69120

2200 3180 4400 5920 7720

79560 102690 128760 157770 189720

Bolt Stress 45,000 PSI

Torque Ft. Lbs.

Compression Lbs.

6

1215

12

2025

18

3060

30

4185

45

5670

68

7290

90

9090

150

13590

240

18855

368

24795

533

32760

750 1020 1200

41805 51975 63225

1650 2250 3000

75600 89100 103680

3300 4770 6600 8880 11580

119340 154035 193140 236655 284580

60,000 PSI

Torque Ft. Lbs.

Compression Lbs.

8

1620

16

2700

24

4080

40

5580

60

7560

90

9720

120

12120

200

18120

320

25140

490

33060

710

43680

1000 1360 1600

55740 69300 84300

2200 3000 4000

100800 118800 138240

4400 6360 8800 11840 15440

159120 205380 257520 315540 379440

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