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Bolt Torque · Inch & Metric

Bolt
Flange bolting

Torque unit converter

Tightening torque
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Clamp load (preload)
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    Tightening sequence · star (cross) pattern

    Number the bolts 1 to N clockwise. Tighten in star order in each pass, then go round clockwise at 100 % until no nut turns; recheck after about 4 hours. Based on the legacy cross pattern of ASME PCC-1; follow your site bolting procedure and the gasket maker's values.

    All sizes for this grade and K
    Equations and sources
    Tensile stress area As = 0.7854 · (D − 0.9743 / n)² (ASME B1.1; D in, n threads/in) Clamp load F = target % × proof strength × As (SAE / A325 / A490) F = target % × yield strength × As (ASTM A193 / A320 studs: no proof load) Metric stress area As = π/4 · ((d2 + d3)/2)², d2 = d − 0.649519·P, d3 = d − 1.226869·P (ISO 898-1; d, P in mm) Torque T = K · D · F (in·lbf) → ft·lbf = T/12, N·m = ft·lbf × 1.35582 (metric: T [N·m] = K · d [mm] · F [kN])

    Strengths: SAE J429 Grade 2 (proof 55 ksi to ¾ in, 33 ksi above), Grade 5 (85 ksi to 1 in, 74 ksi to 1½ in), Grade 8 (120 ksi); ISO 898-1 proof stress 4.6 = 225, 5.6 = 280, 8.8 = 580 MPa to M16 and 600 above, 10.9 = 830, 12.9 = 970 MPa (to M39); ISO 3506-1 stainless 0.2 % proof stress A2-50 = 210, A2/A4-70 = 450, A4-80 = 600 MPa; ASTM A325/F3125 (85 / 74 ksi), A490 (120 ksi); A193 B7, B16 and A320 L7 yield 105 ksi to 2½ in, 95 ksi to 4 in. Nut factors are typical values; real friction varies widely, so torque control gives roughly ±25 % preload scatter. For critical joints (flanges, pressure equipment) follow the job procedure, the gasket maker's stress and ASME PCC-1. This is a planning aid, not a certified procedure.