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Use Prevailing Torque All-Metal Nut chart if using this style of nut. = Nominal Diameter. = Clamp Load For J429 Grade 5 and 8, FNL Grade 9, A574, Class 4.6, 8.8, 10.9 and 12.9, the clamp loads are listed at 75% of the proof loads specified by the standard. For A307 Grade A, 75% of 36,000 PSI is utilized.
The bolt is stressed up to the proofload value, and if there is no deformation, elongation, or fracture, then the bolt is deemed to have passed. For bolting specifications that do not have a published proofload, it is usually calculated at 92% of minimum yield strength.
The charts below show the ideal tightening torque for each bolt grade for a variety of sizes. The size column also includes the thread count. Identify the grade, size, and thread density of your bolts and refer to the tightening torque columns.
U.S. Recommended Bolt Torque Table. * Sizes from 4 to 10 are in in.-lbs. Sizes from 1/4 up are in ft.-lbs. ** Fine thread figures are for 1-14. Grade 2, 5, and 8 values are for plated bolts.
Torque specifications, especially for critical joints, should be determined under actual assembly conditions due to the many variables involved which are difficult to predict and do affect the torque-tension relationship.
Because there are many variables that affect the torque-tension relationship, the only way to determine the correct torque is through experimentation under actual joint and assembly conditions. Bolt torque chart reference guides include Grade 2, B7, A307, A325, Grade 8, A490, and Grade 5.
Maximum tightening torques for US bolts. This chart displays values for lightly oiled threads. The tension is 70% of yield strength.
