GRADE 5 |
GRADE 8 |
||||||
Coarse Thread |
Coarse Thread |
||||||
Size |
Clamp Load |
Plain (ft. lbs.) |
Plated |
Size |
Clamp Load |
Plain (ft. lbs.) |
Plated (ft. lbs.) |
1/4-20 (.250) |
2025 |
8 |
76 in lbs. |
1/4-20 (.250) |
2850 |
12 |
9 |
5/16-18 (.3125) |
3338 |
17 |
13 ft lbs. |
5/16-18 (.3125) |
4725 |
25 |
18 |
3/8-16 (.375) |
4950 |
31 |
23 ft lbs. |
3/8-16 (.375) |
6975 |
44 |
33 |
7/16-14 (.4375) |
6788 |
50 |
37 ft lbs. |
7/16-14 (.4375) |
9600 |
70 |
52 |
1/2-13 (.500) |
9075 |
76 |
57 ft lbs. |
1/2-13 (.500) |
12750 |
106 |
80 |
9/16-12 (.5625) |
11625 |
109 |
82 ft lbs. |
9/16-12 (.5625) |
16350 |
153 |
115 |
5/8-11 (.625) |
14400 |
150 |
112 ft lbs. |
5/8-11 (.625) |
20325 |
212 |
159 |
3/4-10 (.750) |
21300 |
266 |
200 ft lbs. |
3/4-10 (.750) |
30075 |
376 |
282 |
7/8-9 (.875) |
29475 |
430 |
322 ft lbs. |
7/8-9 (.875) |
41550 |
606 |
454 |
1-8 (1.000) |
38625 |
644 |
483 ft lbs. |
1-8 (1.000) |
54525 |
909 |
682 |
1 1/8-7 (1.125) |
42375 |
794 |
596 ft lbs. |
1 1/8-7 (1.125) |
68700 |
1288 |
966 |
1 1/4-7 (1.250) |
53775 |
1120 |
840 ft lbs. |
1 1/4-7 (1.250) |
87225 |
1817 |
1363 |
1 3/8-6 (1.375) |
64125 |
1470 |
1102 ft lbs. |
1 3/8-6 (1.375) |
103950 |
2382 |
1787 |
1 1/2-6 (1.500) |
78000 |
1950 |
1462 ft lbs. |
1 1/2-6 (1.500) |
126450 |
3161 |
2371 |
GRADE 5 |
GRADE 8 |
||||||
Fine Thread |
Fine Thread |
||||||
Size |
Clamp Load |
Plain (ft. lbs.) |
Plated |
Size |
Clamp Load |
Plain (ft. lbs.) |
Plated (ft. lbs.) |
1/4-28 (.250) |
2325 |
10 |
87 in lbs. |
1/4-28 (.250) |
3263 |
14 |
10 |
5/16-24 (.3125) |
3675 |
19 |
14 ft lbs. |
5/16-24 (.3125) |
5113 |
27 |
20 |
3/8-24 (.375) |
5588 |
35 |
26 ft lbs. |
3/8-24 (.375) |
7875 |
49 |
37 |
7/16-20 (.4375) |
7575 |
55 |
41 ft lbs. |
7/16-20 (.4375) |
10650 |
78 |
58 |
1/2-20 (.500) |
10200 |
85 |
64 ft lbs. |
1/2-20 (.500) |
14400 |
120 |
90 |
9/16-18 (.5625) |
12975 |
122 |
91 ft lbs. |
9/16-18 (.5625) |
18300 |
172 |
129 |
5/8-18 (.625) |
16350 |
170 |
128 ft lbs. |
5/8-18 (.625) |
23025 |
240 |
180 |
3/4-16 (.750) |
23775 |
297 |
223 ft lbs. |
3/4-16 (.750) |
33600 |
420 |
315 |
7/8-14 (.875) |
32475 |
474 |
355 ft lbs. |
7/8-9 (.875) |
45825 |
668 |
501 |
1-12 (1.000) |
42300 |
705 |
529 ft lbs. |
1-12 (1.000) |
59700 |
995 |
746 |
1-14 (1.000) |
32275 |
721 |
541 ft lbs. |
1-14 (1.000) |
61125 |
1019 |
764 |
1 1/8-12 (1.125) |
47475 |
890 |
668 ft lbs. |
1 1/8-12 (1.125) |
77025 |
1444 |
1083 |
1 1/4-12 (1.250) |
59550 |
1241 |
930 ft lbs. |
1 1/4-12 (1.250) |
96600 |
2012 |
1509 |
1 3/8-12 (1.375) |
72975 |
1672 |
1254 ft lbs. |
1 3/8-12 (1.375) |
118350 |
2712 |
2034 |
1 1/2-12 (1.500) |
87750 |
2194 |
1645 ft lbs. |
1 1/2-17 (1.500) |
142275 |
3557 |
2668 |
Tightening Torque Guide for Grade 5 & 8 Hex Cap Screws
This table is based on IFI 5th Edition Technical Data N-12/N-16, using Equation (1) and a torque coefficient, K=0.20 for non plated steel fasteners and K=0.15 for plated fasteners.
These Figures represent an estimate of torque (torque being the measurement of friction, not tension) required to induce given preload (clamp load) in a bolt for non-critical applications only. For critical or special applications where greater control is desired this should be experimentally determined. This applies to washer faced or double chamfered hex nuts (or bolts, if bolt is torqued) having a width across flats of approximately 1.5 times the nominal diameter and having threads free of interference.
Because of the many interrelated variables that directly or indirectly affect friction, such as surface texture, type or coating or finish, lubrication, speed of tightening, human error, etc., it is possible to experience as much as ±25% deviation in preload (clamp load) with the use of a torque wrench.
!!!Attention!!! Our printed catalog contains an incorrect unit for the column of grade 5 plated, both coarse and fine thread. The 1st plated item in both coarse & fine thread should be measured in (in. lbs.) not (ft. lbs.). The remaining items in the column are correctly labeled as (ft. lbs.). This web page table has been corrected.
