Thread Pullout Force Calculator

Source

Pullout load and torque values are calculated using the formulas published in Rivera-Rosario, H. T. & Powell, J. S., "Installation Torque Tables for Noncritical Applications," NASA/TM—2017-219475, Glenn Research Center, April 2017.

Not for flight hardware

The source document explicitly states these tables are NOT TO BE USED FOR FLIGHT HARDWARE or anywhere specific bolt tension (preload) is needed based on specific loads to be carried. This calculator carries the same restriction.

Assumptions in the formula

• Fastener material is stronger than the parent material (stainless steel fasteners, yield = 180 ksi)
• Full engagement assumed — bolt is fully threaded into parent material
• Shear strength: F_s = 0.55 × F_t (aluminum & stainless steel), 0.60 × F_t (carbon steel)
• Torque coefficient K = 0.2 (2A class, no insert, no coating adjustment)
• Assembly torque = 65% of pullout torque (safety factor = 1.538)
• Pullout formula already includes a safety factor of 3 in the denominator
• Minimum 3 threads of engagement required
• Machine screws only — not structural bolts or bolted joints

Sources of variation

Actual pullout strength depends on factors not captured here:

• Pilot hole diameter and quality of tapped threads
• Exact material grade, heat treatment, and hardness
• Thread class (1A, 2A, 3A) and fit quality
• Surface finish, coatings, and lubrication
• Fastener material and actual nut factor K
• Temperature, vibration, and loading history

Intended use

This calculator is for educational and preliminary reference only. Test results from the NASA study showed actual strip-out torques generally above (but sometimes below) calculated values. For any structural, safety-critical, or flight application, consult certified fastener specifications and qualified engineering analysis.

No warranty

Abeyant Maker makes no warranty regarding the accuracy or fitness for purpose of any calculated values. Users assume full responsibility for verifying values before application.