SAE Bolt Torque Specifications

Introduction:

Do you find yourself working on projects, grabbing Grade 5 or Grade 8 bolts from the hardware store, but not knowing what to torque them to?

This should help.

Suggested Starting Values:

The below estimated torque calculations are only offered as a guide. Use of its content by anyone is the sole responsibility of that person and they assume all risk. Due to many variables that affect the torque-tension relationship like human error, surface texture, and lubrication the only way to determine the correct torque is through experimentation under actual joint and assembly conditions.

Grade 5 Bolts:

Bolt Size	TPI (Threads Per Inch)	Tightening Torque (ft lbs)
		Galvanized	Plain
1⁄4	20	11	8
5⁄16	18	22	17
3⁄8	16	39	31
7⁄16	14	62	49
1⁄2	13	94	75
9⁄16	12	136	109
5⁄8	11	188	150
3⁄4	10	333	266
7⁄8	9	537	429
1	8	805	644
11⁄8	7	992	794
11⁄4	7	1,400	1,120
13⁄8	6	1,836	1,469
11⁄2	6	2,438	1,950
13⁄4	5	2,857	2,286
2	41⁄2	4,297	3,438
21⁄4	41⁄2	6,284	5,027
21⁄2	4	8,594	6,875
23⁄4	4	11,651	9,321
3	4	15,391	12,313
* SAE J429 grade 5 bolts do not exceed 1-1/2″ diameter.

Grade 8 Bolts:

Bolt Size	TPI (Threads Per Inch)	Tightening Torque (ft lbs)
		Plain	Lubricated
1⁄4	20	12	6
5⁄16	18	25	12
3⁄8	16	44	22
7⁄16	14	70	35
1⁄2	13	107	53
9⁄16	12	154	77
5⁄8	11	212	106
3⁄4	10	376	188
7⁄8	9	606	303
1	8	909	454
11⁄8	7	1,287	644
11⁄4	7	1,875	938
13⁄8	6	2,382	1,191
11⁄2	6	3,161	1,581
13⁄4	5	4,988	2,494
2	41⁄2	7,500	3,750
21⁄4	41⁄2	10,969	5,484
21⁄2	4	15,000	7,500
23⁄4	4	17,794	8,897
3	4	23,507	11,753
31⁄4	4	30,286	15,143
31⁄2	4	38,266	19,133
33⁄4	4	47,545	23,773
4	4	58,100	29,085
* SAE J429 grade 8 bolts do not exceed 1-1/2″ diameter.

Notes:

Values calculated using industry accepted formula T = KDP where T = Torque, K = torque coefficient (dimensionless), D = nominal diameter (inches), P = bolt clamp load, lb.

K values: waxed (e.g. pressure wax as supplied on high strength nuts) = .10, hot dip galvanized = .25, and plain non-plated bolts (as received) = .20.

Torque has been converted into ft/lbs by dividing the result of the formula by 12

All calculations are for Coarse Thread Series (UNC).

Grade 2 calculations only cover fasteners 1⁄4“-3⁄4” in diameter up to 6″ long; for longer fasteners the torque is reduced significantly.

Clamp loads are based on 75% of the minimum proof loads for each grade and size.

Proof load, stress area, yield strength, and other data is based on IFI 7th Edition (2003) Technical Data N-68, SAE J429, ASTM A307, A325, A354, A449, and A490.