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Bolt Torque
Results are for reference only. Check these numbers against other sources — and the fastener manufacturer's spec — before relying on them for a real joint.
Set-up define the joint
Bolt size
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Property class / grade
Lubrication / finish condition
Target torque
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Relationships
What drives the torque spec
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Fastener library
Standard sizes & tensile stress areas
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Field notes
Why torque is only an estimate of tension
Bolt Torque & Preload — short-form torque-tension formula T = K·D·F, using
standard ISO tensile stress areas (metric) or published reference areas (UNC), and typical published proof
strengths per property class. Nut factor K values are widely-cited industry references but real friction
varies with surface condition, plating, and batch — actual achieved torque for the same target preload can
easily vary ±25–30% , shown here as a range. For safety-critical, structural, or warranty-governed joints,
always use the fastener manufacturer's stamped torque spec, not this estimate. Not a substitute for a calibrated
torque wrench and a documented procedure.