The data focuses on recommended tightening torque for a standard ¼-20 UNC Grade 5 equivalent bolt (or similar high-strength condition) to provide a consistent baseline. Actual values depend on specific alloy condition, heat treatment, lubrication, and application standards (e.g., NASM, ASME).

Key Factors Influencing Torque:

• Ultimate Tensile Strength (UTS): Primary driver for torque capacity.

• Yield Strength: Determines clamp load before permanent deformation.

• Material Ductility & Galling Tendency: Affects assembly behavior and may require lubricants or plating.

• Modulus of Elasticity: Influences stiffness and load distribution.

• Torque Formula (Simplified):T = K * d * F where T = Torque (lb-in or Nm), K = Torque coefficient (friction factor), d = Nominal diameter, F = Desired preload (clamp force). F is typically ~75% of proof load for critical joints.

Torque Data Comparison Table (Baseline: ¼-20 UNC Fastener)

Critical Considerations & Analysis

1. Strength vs. Torque: There is a direct correlation between material yield strength and achievable clamp load/torque. MP159, MP35N, and high-strength Ni/Co superalloys (Waspaloy, Inconel 718) allow the highest torque values, followed by PH steels (17-4, PH 13-8) and Titanium. Pure/soft metals (Nickel 200, Tantalum, Zirconium) have the lowest torque ratings.

2. Galling & Seizing (Critical for Assembly):

   • High Risk: Austenitic stainless steels (especially 300 series), Titanium, Aluminum, Nickel alloys, and Zirconium. These materials often require anti-gallant lubricants/coatings (e.g., molybdenum disulfide, copper-based, or proprietary dry films).

   • Lower Risk: Nitronic 60 is specifically designed for high galling resistance.

3. Lubrication (Factor K): The torque values above assume a "dry" (unlubricated) condition with a torque coefficient K ~ 0.20. Using lubricant (e.g., oil, Molykote) can reduce K to ~0.14-0.16, reducing required torque by ~20-30% to achieve the same clamp load. Always follow specific fastener specifications.

4. Temperature & Corrosion:

   • High-Temp Applications: Inconel, Incoloy, Nimonic, Waspaloy, Alloy 330, 310SS, and Molybdenum retain strength at elevated temperatures. Torque values drop at high temperature.

   • Corrosion Resistance: Hastelloy, Alloy 20, 254 SMO, AL-6XN, Tantalum, Zirconium are chosen for aggressive environments, not primarily for strength.

5. Practical Recommendation: For critical applications (aerospace, nuclear, subsea), do not rely solely on generic torque tables. Use:

   • Engineering Standards: Refer to specific material/fastener specs (e.g., SAE AS8879 for Ti, MIL-HDBK-60).

   • Torque-Tension Testing: Empirical testing for the exact fastener system (material, plating, lubricant, hole condition) is ideal.

   • Direct Tension Indicating Methods: Use load washers, ultrasonic measurement, or turn-of-nut method for precision.

Disclaimer: This data is for comparative and estimation purposes only. Always consult material certification data, RAYCHIN fastener manufacturer specifications, and applicable design codes for final torque values.