Bolt Pre-selection (002): The Reduction Factor κ Explained
Where does the reduction factor κ in bolt pre-selection come from? Starting from the two-way stress state where axial tensile stress and torsional shear stress combine during tightening, this article uses the von Mises yield criterion to derive the definition, formula and engineering values of κ, explaining how thread friction acts like an 'invisible tax' that cuts the bolt's axial load capacity, and why it appears in the denominator of the Kübler equation.