Bolt Tightening Torque

When tightening bolts on your equipment, it is sometimes helpful to know the recommended torque. On the vast majority of bolts, you can just tighten until it feels good, but a few critical fasteners should be checked with a torque wrench. Your owner’s manual should give you a torque value for critical fasteners, but you may occasionally need to find the generally recommended torque for other fasteners. If so, the table below should help you. These figures are for clean, dry steel bolts. The U.S thread information is excerpted from Standard Handbook of Fastening and Joining by R.O. Parmley (1977, McGraw-Hill) and the metric information from various websites.

U.S. Bolt Threads
Thread Size	SAE Grade 2	SAE Grade 5	SAE Grade 8
Coarse thread
¼ - 20	49-65 lb-in	75-100 lb-in	107-143 lb-in
5/16 -18	101-134 lb-in	157-210 lb-in	220-305 lb-in
3/8 - 16	15-20 lb-ft	23-31 lb-ft	33-44 lb-ft
7/16 – 14	24-30 lb-ft	37-50 lb-ft	53-70 lb-ft
½ -13	37-49 lb-ft	57-75 lb-ft	80-107 lb-ft
9/16 – 12	53-70 lb-ft	82-109 lb-ft	115-154 lb-ft
5/8 – 11	73-97 lb-ft	113-151 lb-ft	159-211 lb-ft
¾ - 10	129-173 lb-ft	200-266 lb-ft	282-376 lb-ft
Fine thread
¼ - 28	55-75 lb-in	85-115 lb-in	120-163 lb-in
5/16 – 24	112-150 lb-in	173-230 lb-in	245-325 lb-in
3/8 – 24	17-23 lb-ft	26-35 lb-ft	37-50 lb-ft
7/16 – 20	27-36 lb-ft	42-55 lb-ft	59-78 lb-ft
½ - 20	41-55 lb-ft	64-85 lb-ft	90-120 lb-ft
9/16 – 18	59-79 lb-ft	92-122 lb-ft	129-172 lb-ft
5/8 – 18	83-110 lb-ft	128-170 lb ft	180-240 lb-ft
¾ - 16	144-193 lb-ft	223-298 lb-ft	315-420 lb-ft

Metric Bolt Threads
Thread Size	Low Grade	Grade 8.8	Grade 10.9	Grade 12.9
5 mm		5 lb-ft	7 lb-ft
6 mm	3-5 lb-ft	7 lb-ft	10 lb-ft	12 lb-ft
8 mm	8-12 lb-ft	17 lb-ft	24 lb-ft	29 lb-ft
10 mm	15-22 lb-ft	33 lb-ft	47 lb-ft	57 lb-ft
12 mm	39 lb-ft	59 lb-ft	83 lb-ft	100 lb-ft
14 mm	60 lb-ft	101 lb-ft	131 lb-ft	158 lb-ft
16 mm	60-94 lb-ft	146 lb-ft	202 lb-ft	247 lb-ft
18 mm	60-130 lb-ft	201 lb-ft	283 lb-ft	340 lb-ft
20 mm	166-188 lb-ft	285 lb-ft	401 lb-ft	482 lb-ft
Multiply lb-ft by 1.3558 to get N-m