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Torque Values

Torque With Wrench

During automotive repair and replacement work, fasteners such as nuts and bolts are often replaced in the process. It's important to not only use the correct size of fastener, but also the correct grade and torque. We've talked about identifying grade markings on bolt heads already.

Now let's look at how those specifications match to torque values applied to those bolts and their corresponding nuts. For metric bolt torque values, click here.

The following chart is the suggested maximum torque values for threaded bolts in ft-pounds. If your manufacturer recommends a specific torque setting for an application, that will override this chart. We assume non-lubricated, unfinished products. Standard common grades are listed - most others are in-between and can be guessed using the below numbers.

Bolt Size (inches) Threads/inch (course) SAE 0-2 low carbon SAE Grade 5 mid carbon SAE Grade 8 mid carbon alloy
1/4 20 6 10 14
5/16 18 12 19 29
3/8 16 20 33 47
7/16 14 32 54 78
1/2 13 47 78 119
9/16 12 69 114 169
5/8 11 96 154 230
3/4 10 155 257 380
7/8 9 206 382 600
1 8 310 587 880
1-1/4 7 675 1105 1975
1-1/2 6 1100 1775 3200

Remember also that bolts are about tensile (pulling) not sheer (cutting) strength. So a bolt can hold its rated weight/pressure along the length of its shaft, but cannot hold the same on any one point perpendicular to its shaft.

In fact, the higher the metal grade of the bolt (i.e. the more carbon it has), the less sheer strength it has. Engineers keep this in mind when designing applications, so be sure you're using the same grade of fastener (not more, not less) as is specified for your application.

Head bolts, for instance, are often Grade 8 (high carbon) and unfinished (no zinc or other finish). Diameter will depend on application, but typically is around 1/2 inch, allowing for 119 pounds of torque.

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