Torque Tolerance Scatter Calculator Online (Preload Range)

Torque Tolerance Scatter Calculator (Preload Range)

A process sheet says "tighten to 30 N.m", yet actual preload in the same batch can differ by a factor of two - torque-controlled tightening scatters preload by 25-40%. The designer must answer: will the worst case yield the bolt, and is the minimum preload still enough against loosening and slip? This calculator takes target torque, size, grade and scatter percentage, and outputs the preload range with a yield-ratio verdict.

The relation: torque converts to preload through the torque coefficient K, F = T / (K x d). K varies with thread friction, bearing friction and coating, and since torque and preload are linearly proportional, torque scatter passes straight through. Two red lines: F_max within 90% of yield preload, and F_min above the minimum clamp force for anti-loosening.

When both red lines fail, switch to torque-angle control - use our turn-of-nut calculator; determine targets with the torque calculator. Three levers to cut scatter: consistent lubrication (stable K), calibrated click-type wrenches on a regular schedule, and better bearing-surface conditions. Zhuhai Jiali Hardware supplies Dacromet and lubricated zinc fasteners with stable K - contact us.