Torque-Tension Relationship for ASTM A193 B7 Bolts and Studs
Nominal
Dia.
(in.)
1/4
1/4
5/16
5/16
3/8
3/8
7/16
7/16
1/2
1/2
9/16
9/16
5/8
5/8
3/4
3/4
7/8
7/8
1
1
1
1
1
1
1
1
1
1
1
2
2
2
1/8
1/8
1/4
1/4
1/2
1/2
5/8
3/4
7/8
1/4
1/2
Threads
Per Inch
20
28
18
24
16
24
14
20
13
20
12
18
11
18
10
16
9
14
8
14
7
8
7
8
8
6
8
8
8
8
8
8
Minimum
Tensile
Strength
(lbs.)
3978
4547
6554
7258
9686
10979
13289
14840
17737
19994
22743
25373
28250
31995
41808
46620
57717
63684
75718
84986
95409
98807
121139
124963
186480
175657
221841
260269
301766
346330
444663
555267
Minimum
Yield
Strength
(lbs.)
3341
3819
5505
6097
8136
9222
11162
12465
14899
16795
19104
21313
23730
26876
35118
39161
48482
53495
63603
71388
80144
82998
101757
104969
156644
147551
186346
218626
253483
290917
373517
466425
Est.
Shear
Strength
(lbs.)
2016
2441
3401
3931
5083
6063
6997
8173
9425
11146
12150
14159
15131
17999
22643
26344
31438
36035
41316
48473
51969
54570
66722
69664
105376
97013
125992
148450
172748
198887
256688
321851
Clamp
Load
(lbs)
2506
2864
4129
4573
6102
6916
8372
9349
11175
12596
14328
15985
17798
20157
26339
29371
36362
40121
47702
53541
60108
62248
76318
78727
117483
110664
139760
163970
190112
218188
280138
349819
Tightening Torque
K = 0.12
K = 0.15
K = 0.20
(ft-lbs)
6
7
13
14
23
26
37
41
56
63
81
90
111
126
198
220
318
351
477
535
676
700
954
984
1762
1660
2271
2869
3565
4364
6303
8745
(ft-lbs)
8
9
16
18
29
32
46
51
70
79
101
112
139
157
247
275
398
439
596
669
845
875
1192
1230
2203
2075
2839
3587
4456
5455
7879
10932
(ft-lbs)
10
12
22
24
38
43
61
68
93
105
134
150
185
210
329
367
530
585
795
892
1127
1167
1590
1640
2937
2767
3785
4782
5941
7273
10505
14576
The torque values can only be achieved if nut (or tapped hole) has a proof load greater than or equal to the bolt's minimum ultimate tensile strength.
Clamp load calculated as 75% of the yield strength for the B7 specified in ASTM A193.
Torque values calculated from formula T=KDF, where
Coatings such as Teflon or Xylan offer extremely low coefficients of friction. Often we will experience K values around 0.12 or even lower.
K = 0.15 for "lubricated" conditions and K = 0.20 for "dry" conditions
D = Nominal Diameter
F = Clamp Load
Tensile and Yield strengths in accordance with ASTM A193
Minimum ultimate tensile strength: 125,000 PSI (up through 2-1/2") and 115,000 PSI (over 2-1/2 through 4)
Minimum yield strength: 105,000 PSI (up through 2-1/2") and 95,000 PSI (over 2-1/2 through 4)
Estimated Shear Strength based off of 60% of minimum tensile strength using the thread root area. It is not part of the ASTM A193 specification.
Caution: All material included in this chart is advisory only, and its use by anyone is voluntary. In developing this information, Fastenal has made a
determined effort to present its contents accurately. Extreme caution should be used when using a formula for torque/tension relationships. Torque
is only an indirect indication of tension. Under/over tightening of fasteners can result in costly equipment failure or personal injury.
Rev 3-4-09