9/16-12 bolt tightening torque
A 9/16-12 bolt in SAE Grade 5, dry, torques to about 109 lb-ft (147 N·m) at 75% of proof load.
0.5625″ major dia · 12 TPI · At = 0.182 in² · clean, undamaged threads
9/16-12 torque by grade and lubrication (lb-ft)
| Grade | Dry / as-received steel K=0.2 | Zinc plated K=0.22 | Lubricated (light oil) K=0.15 | Molybdenum disulfide K=0.1 | Anti-seize compound K=0.13 | Waxed / PTFE K=0.1 |
|---|---|---|---|---|---|---|
| SAE Grade 2 | 70.4 | 77.4 | 52.8 | 35.2 | 45.7 | 35.2 |
| SAE Grade 5 | 109 | 120 | 81.6 | 54.4 | 70.7 | 54.4 |
| SAE Grade 8 | 154 | 169 | 115 | 76.8 | 99.8 | 76.8 |
| 18-8 Stainless | 51.2 | 56.3 | 38.4 | 25.6 | 33.3 | 25.6 |
Proof strengths per SAE J429; tensile stress area per ASME B1.1. Values at 75 % of proof load.
Caution — match the column to your assembly. The same bolt can need half the torque lubricated versus dry, because K drops from ~0.20 to ~0.10. A dry-torque figure applied to a lubricated bolt over-tightens it and can snap it.
How the value is worked out
Torque isn't the goal — clamp load is. Tightening stretches the bolt into a controlled tension that squeezes the joint together. For a 9/16-12 in SAE Grade 8 at 75 % of proof load that target tension is about 16400 lbf; torque is just the indirect lever used to reach it, and the relationship runs through the nut factor K. The tensile stress area of the 9/16-12 thread is 0.182 in²; multiply it by the grade's proof strength and by 0.75 to get the preload F, then feed F into T = K·D·F for the table above.
Choosing the right friction condition
This is the input people get wrong most often. K bundles every friction loss in the joint — under the head and across the threads — and it moves the torque dramatically: dry, a 9/16-12 in SAE Grade 8 wants about 154 lb-ft; with light oil only 115 lb-ft; with MoS₂ roughly 76.8 lb-ft — for the same target tension. Always match the column to what is actually on the threads.
Grade matters as much as size
SAE Grade 2 tolerates roughly 70.4 lb-ft dry; SAE Grade 8 in the same diameter takes about 154 lb-ft because it safely holds far more tension. Torquing a lower grade to a higher grade's table is another classic way to fail a joint — check the head markings before picking a row. And remember: torque-wrench control scatters ±25 % in practice; for safety-critical joints use angle-control or direct tension measurement.
Tapping the mating hole? 9/16-12 tap drill size
References
- SAE J429 — Mechanical and material requirements for externally threaded fasteners (proof strengths).
- ASME B1.1 — Unified inch screw threads: tensile stress area.
- Machinery’s Handbook — torque–preload relation and nut-factor scatter.
Last reviewed: 2026-07 · Calculation method & assumptions