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FAA torque reference
AC 43.13-1B, Table 7-1 · inch-pounds (in-lb)
Use the manufacturer's specified torque first
This table applies when specific torque is not supplied by the manufacturer (paragraph 7-40i). Its values are derived from oil-free cadmium-plated threads. The recommended-installation columns concern bolts loaded primarily in shear and the named nut types; they are not a general torque recommendation for every AN or NAS part.
Add friction drag torque to the desired torque (7-40c–d). For castle nuts, align at the minimum recommended torque plus drag; never exceed the maximum plus drag (7-40f). Maximum allowable tightening limits below are separate from recommended installation ranges.
fine thread series
| Thread | Recommended installation (in-lb) | Maximum allowable tightening (in-lb) | ||
|---|---|---|---|---|
| Tension type nuts MS20365 and AN310 (40,000 psi in bolts) | Shear type nuts MS20364 and AN320 (24,000 psi in bolts) | Nuts MS20365 and AN310 (90,000 psi in bolts) | Nuts MS20364 and AN320 (54,000 psi in bolts) | |
| 8-36 | 12-15 | 7-9 | 20 | 12 |
| 10-32 | 20-25 | 12-15 | 40 | 25 |
| 1/4-28 | 50-70 | 30-40 | 100 | 60 |
| 5/16-24 | 100-140 | 60-85 | 225 | 140 |
| 3/8-24 | 160-190 | 95-110 | 390 | 240 |
| 7/16-20 | 450-500 | 270-300 | 840 | 500 |
| 1/2-20 | 480-690 | 290-410 | 1100 | 660 |
| 9/16-18 | 800-1000 | 480-600 | 1600 | 960 |
| 5/8-18 | 1100-1300 | 600-780 | 2400 | 1400 |
| 3/4-16 | 2300-2500 | 1300-1500 | 5000 | 3000 |
| 7/8-14 | 2500-3000 | 1500-1800 | 7000 | 4200 |
| 1-14 | 3700-5500 | 2200-3300* | 10,000 | 6000 |
| 1-1/8-12 | 5000-7000 | 3000-4200* | 15,000 | 9000 |
| 1-1/4-12 | 9000-11,000 | 5400-6600* | 25,000 | 15,000 |
coarse thread series
| Thread | Recommended installation (in-lb) | Maximum allowable tightening (in-lb) | ||
|---|---|---|---|---|
| Tension type nuts MS20365 and AN310 (40,000 psi in bolts) | Shear type nuts MS20364 and AN320 (24,000 psi in bolts) | Nuts MS20365 and AN310 (90,000 psi in bolts) | Nuts MS20364 and AN320 (54,000 psi in bolts) | |
| 8-32 | 12-15 | 7-9 | 20 | 12 |
| 10-24 | 20-25 | 12-15 | 35 | 21 |
| 1/4-20 | 40-50 | 25-30 | 75 | 45 |
| 5/16-18 | 80-90 | 48-55 | 160 | 100 |
| 3/8-16 | 160-185 | 95-100 | 275 | 170 |
| 7/16-14 | 235-255 | 140-155 | 475 | 280 |
| 1/2-13 | 400-480 | 240-290 | 880 | 520 |
| 9/16-12 | 500-700 | 300-420 | 1100 | 650 |
| 5/8-11 | 700-900 | 420-540 | 1500 | 900 |
| 3/4-10 | 1150-1600 | 700-950 | 2500 | 1500 |
| 7/8-9 | 2200-3000 | 1300-1800 | 4600 | 2700 |
* Estimated corresponding values. The above torque values may be used for all cadmium-plated steel nuts of the fine or coarse thread series which have approximately equal number of threads and equal face bearing areas.
Governing FAA installation paragraphs
- 7-40 (p.7-6): The importance of correct torque application cannot be overemphasized. Undertorque can result in unnecessary wear of nuts and bolts, as well as the parts they secure. Overtorque can cause failure of a bolt or nut from overstressing the threaded areas.
- 7-40 NOTE (p.7-6): Be sure that the torque applied is for the size of the bolt shank not the wrench size.
- 7-40a (p.7-6): Calibrate the torque wrench at least once a year, or immediately after it has been abused or dropped, to ensure continued accuracy.
- 7-40b (p.7-6): Be sure the bolt and nut threads are clean and dry, unless otherwise specified by the manufacturer.
- 7-40c (p.7-6): Run the nut down to near contact with the washer or bearing surface and check the friction drag torque required to turn the nut. Whenever possible, apply the torque to the nut and not the bolt. This will reduce rotation of the bolt in the hole and reduce wear.
- 7-40d (p.7-7): Add the friction drag torque to the desired torque. This is referred to as “final torque,” which should register on the indicator or setting for a snap-over type torque wrench.
- 7-40e (p.7-7): Apply a smooth even pull when applying torque pressure. If chattering or a jerking motion occurs during final torque, back off the nut and retorque.
- 7-40e NOTE (p.7-7): Many applications of bolts in aircraft/engines require stretch checks prior to reuse. This requirement is due primarily to bolt stretching caused by overtorquing.
- 7-40f (p.7-7): When installing a castle nut, start alignment with the cotter pin hole at the minimum recommended torque plus friction drag torque.
- 7-40f NOTE (p.7-7): Do not exceed the maximum torque plus the friction drag. If the hole and nut castellation do not align, change washer or nut and try again. Exceeding the maximum recommended torque is not recommended.
- 7-40g (p.7-7): When torque is applied to bolt heads or capscrews, apply the recommended torque plus friction drag torque.
- 7-40h (p.7-7): If special adapters are used which will change the effective length of the torque wrench, the final torque indication or wrench setting must be adjusted accordingly. Determine the torque wrench indication or setting with adapter installed as shown in figure 7-2.
- 7-40i (p.7-7): Table 7-1 shows the recommended torque to be used when specific torque is not supplied by the manufacturer. The table includes standard nut and bolt combinations, currently used in aviation maintenance.
- 7-64a (p.7-11): DO NOT use self-locking nuts on parts subject to rotation.
- 7-64f (p.7-11): Fiber or nylon self-locking nuts are not installed in areas where temperatures exceed 250 °F. After the nut has been tightened, make sure the bolt or stud has at least one thread showing past the nut. DO NOT reuse a fiber or nylon locknut, if the nut cannot meet the minimum prevailing torque values. (See table 7-2.)
- 7-65a NOTE (p.7-12): Cadmium-plated nuts are restricted for use in temperatures not to exceed 450 °F. When used in temperatures in excess of 450 °F, the cadmium will diffuse into the base material causing it to become very brittle and subject to early failure.
Reference only: the controlling drawing, its process spec and the manufacturer's installation instructions govern. How to use these answers