REFERENCE PAGE FOR USING THE RIGHT BOLT BASED ON GRADE
One of the biggest mistakes in automotive work, is using the wrong kind of bolt. All automotive manufacturers use grade 8 or higher nuts and bolts on their vehicles. There are many that do not understand bolts by grade and torque specifications. Don't make this mistake by thinking that a bolt is a bolt, because it isn't.
There have been engine brackets break off or trailer hitches break from using the wrong bolts. It is even more common with shock absorbers. Many times I have seen shocks come loose because an inferior bolt was used.
I have seen head gaskets blow out because a low grade bolt was used to replace an OEM bolt. Lower grade bolts can't withstand the torque that higher grades can.
All heads of bolts, have markings and indicators to specify the grade of the bolt. It is crucial to use the right kind of bolt per application. Always pay close attention to the head of a bolt to ensure it is the right strength bolt. It's always a good practice to use a torque wrench when tightening bolts.
If you are unsure or just don't understand how bolts by grades work, feel free to contact me, and I will do my best to help.
Bolt Grade Markings
US Bolts
Metric Bolts
US Recommended Torque by Grade
| Bolt Size | Grd 2 Cors | Grd 2 Fine | Grd 5 Cors | Grd 5 Fine | Grd 8 Cors | Grd 8 Fine | 18-8 S/S Crs | 18-8 S/S Fine |
|---|---|---|---|---|---|---|---|---|
| 1/4" | 4 ft-lbs | 4.7 ft-lbs | 6.3 ft-lbs | 7.3 ft-lbs | 9 ft-lbs | 10 ft-lbs | 6.3 ft-lbs | 7.8 ft-lbs |
| 5/16" | 8 ft-lbs | 9 ft-lbs | 13 ft-lbs | 14 ft-lbs | 18 ft-lbs | 20 ft-lbs | 11 ft-lbs | 11.8 ft-lbs |
| 3/8" | 15 ft-lbs | 17 ft-lbs | 23 ft-lbs | 26 ft-lbs | 33 ft-lbs | 37 ft-lbs | 20 ft-lbs | 22 ft-lbs |
| 7/16" | 24 ft-lbs | 27 ft-lbs | 37 ft-lbs | 41 ft-lbs | 52 ft-lbs | 58 ft-lbs | 31 ft-lbs | 33 ft-lbs |
| 1/2" | 37 ft-lbs | 41 ft-lbs | 57 ft-lbs | 64 ft-lbs | 80 ft-lbs | 90 ft-lbs | 43 ft-lbs | 45 ft-lbs |
| 9/16" | 53 ft-lbs | 59 ft-lbs | 82 ft-lbs | 91 ft-lbs | 115 ft-lbs | 129 ft-lbs | 57 ft-lbs | 63 ft-lbs |
| 5/8" | 73 ft-lbs | 83 ft-lbs | 112 ft-lbs | 128 ft-lbs | 159 ft-lbs | 180 ft-lbs | 93 ft-lbs | 104 ft-lbs |
| 3/4" | 125 ft-lbs | 138 ft-lbs | 200 ft-lbs | 223 ft-lbs | 282 ft-lbs | 315 ft-lbs | 128 ft-lbs | 124 ft-lbs |
| 7/8" | 129 ft-lbs | 144 ft-lbs | 322 ft-lbs | 355 ft-lbs | 454 ft-lbs | 501 ft-lbs | 194 ft-lbs | 193 ft-lbs |
| 1" | 188 ft-lbs | 210 ft-lbs | 483 ft-lbs | 541 ft-lbs | 682 ft-lbs | 764 ft-lbs | 287 ft-lbs | 289 ft-lbs |
The above values are in Ft-Lbs
Metric Recommended Torque by Grade
| Bolt Size | Grade 8.8 | Grade 10.9 | Grade 12.9 |
|---|---|---|---|
| M3 | 0.8 ft-lbs | 1.1 ft-lbs | 1.3 ft-lbs |
| M4 | 1.8 ft-lbs | 2.6 ft-lbs | 3.1 ft-lbs |
| M5 | 3.6 ft-lbs | 5.1 ft-lbs | 6.2 ft-lbs |
| M6 | 7 ft-lbs | 10 ft-lbs | 12 ft-lbs |
| M8 | 17 ft-lbs | 25 ft-lbs | 29 ft-lbs |
| M10 | 33 ft-lbs | 48 ft-lbs | 58 ft-lbs |
| M12 | 60 ft-lbs | 85 ft-lbs | 102 ft-lbs |
| M14 | 97 ft-lbs | 137 ft-lbs | 165 ft-lbs |
| M16 | 150 ft-lbs | 208 ft-lbs | 250 ft-lbs |
| M18 | 201 ft-lbs | 287 ft-lbs | 342 ft-lbs |
| M20 | 282 ft-lbs | 398 ft-lbs | 479 ft-lbs |
| M22 | 390 ft-lbs | 552 ft-lbs | 664 ft-lbs |
| M24 | 499 ft-lbs | 750 ft-lbs | 843 ft-lbs |
| M27 | 746 ft-lbs | 1051 ft-lbs | 1266 ft-lbs |
| M30 | 982 ft-lbs | 1383 ft-lbs | 1657 ft-lbs |
| M33 | 1331 ft-lbs | 1875 ft-lbs | 2250 ft-lbs |
| M36 | 1717 ft-lbs | 2407 ft-lbs | 2895 ft-lbs |
The above values are in Ft-Lbs
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Secrets To General Bolt Torque by Bolt Size and Grades
Download your own free copy: Learn what general bolt torque specification to what size bolt and grade, both in US and Metric. Ideal if you do not know the torque spec of a bolt or nut...