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Aircraft Fastener Torque Reference

Standard torque values for AN, NAS, and MS aircraft bolts and fasteners. Look up torque ranges by bolt size, material, and lubrication — in in-lb, ft-lb, and N·m. Based on AC 43.13-1B and manufacturer data.

Torque Lookup

Always verify torque values against the aircraft's AMM or CMM. Manufacturer-specified torques always take precedence over general tables.

Torque Unit Converter

in-lb
ft-lb
N·m
kgf·cm

AN Bolt Standard Torque Table (Steel, Dry)

Source: FAA AC 43.13-1B, Table 7-1. Values are for steel, cadmium-plated bolts with dry (unlubricated) nuts. Reduce by 20% for lubricated/wet installation.

Bolt Diameter Thread Min (in-lb) Max (in-lb) Min (N·m) Max (N·m)

Torque Application Guidelines

Wet vs. Dry Torque
Wet Torque = Dry Torque × 0.80

Apply 80% of the dry torque value when using anti-seize compound, engine oil, or other lubricants on threads.

Torque + Angle (Prevailing Torque)
Effective Torque = Applied Torque − Prevailing Torque

For self-locking nuts, subtract the prevailing torque (run-down torque) from the final reading to get the effective clamping torque.

Pro Tip for AMEs: Always use a calibrated torque wrench within its 20–80% of full-scale range for best accuracy. Record torque wrench serial number and calibration date in the work order per EASA Part-145 / FAA Part-43.
General Torquing Rules
  • Inspect threads for damage, corrosion, or contamination before assembly.
  • Apply torque smoothly and steadily — avoid jerking or impact application.
  • For castellated nuts, torque to the minimum value first; if the cotter pin hole does not align, continue to the next slot (do not back off).
  • Never use extensions on a torque wrench without correcting the torque value for lever arm length.
  • Manufacturer AMM/CMM torque values always supersede general tables.
  • Re-torque after thermal cycling if specified in the maintenance manual.

Frequently Asked Questions

AN (Army-Navy) fasteners are the original military standard, still widely used in general aviation. NAS (National Aerospace Standard) fasteners are higher-strength, closer-tolerance fasteners used in commercial and military aircraft. MS (Military Standard) covers a broad range of hardware including bolts, nuts, washers, and pins. All three are interchangeable within their respective specifications.

Torque is a combination of thread friction and clamping force. Lubrication reduces thread friction, meaning the same applied torque produces a higher clamping force. To achieve the same clamping force as a dry installation, the torque must be reduced (typically by 20%) to avoid over-stressing the fastener or joint.

A prevailing torque nut (e.g., MS21042, NAS1291) has a locking feature (nylon insert, distorted thread, or oval top) that requires torque to run it down even before it contacts the bearing surface. When applying final torque, the prevailing torque must be measured and subtracted from the total torque reading to determine the actual clamping torque.

Self-locking nuts may be reused if the prevailing torque still meets the minimum specified value when run down. Per AC 43.13-1B, a self-locking nut should be replaced if the prevailing torque falls below the minimum specified or if the nut shows signs of damage, corrosion, or thread wear.