// multi-utility computation suite · offline · instant · precise
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eng.bolted-joint-preload Calculator
Calculates bolt preload from tightening torque, joint stiffness ratio, and bolt elastic constants for critical bolted joint design. Preload provides clamping force that prevents joint separation under dynamic loading — inadequate preload leads to fatigue failure from full applied load cycling.
Inputs
Bolt Diameter Mm
Distance across a circle through its centre. Always confirm units match the rest of the calculation.
Bolt Grade
Reference formula or conversion factor shown for context.
Torque Nm
Rotational force (N·m) = force × perpendicular lever arm. Engine torque peaks at lower RPM; horsepower peaks higher.
Friction Coefficient
Reference formula or conversion factor shown for context.
Results
preload F (kN) from torque
Rotational force (N·m) = force × perpendicular lever arm. High torque at low RPM is ideal for hauling; high RPM suits high-speed applications.
proof load 75% (kN)
Sample size or count used in the calculation.
% of proof load
Reference formula or conversion factor shown for context.
T = K×d×F
Reference formula or conversion factor shown for context.
K uncertainty
Sample size or count used in the calculation.
grade 8.8 proof stress
Internal force per unit area (Pa or MPa). Must stay below yield strength in service. Beyond yield: permanent deformation. Beyond tensile strength: fracture.