Bolt tightening torque & shear stress

modified2026-07-21statusfinished

Threaded-fastener preload torque and tensile/shear stress checks for steel bolts.

[5.3] Governing equations

$$T=K\cdot D\cdot F_i,\quad \sigma_t=\frac{F_i}{A_s},\quad \tau=\frac{16T}{\pi d_r^3}$$

$K$ nut factor (0.15–0.20 typical lubricated steel), $D$ nominal diameter, $A_s$ tensile stress area, $d_r$ root (minor) diameter. Source: Engineering ToolBox.

FIG. 01 — torque T develops axial preload Fi in the bolt shank

Nominal diameter D (mm) Nut factor K Target preload Fi (N) Tensile stress area As (mm²) Root diameter dr (mm)

Torque T	—
Tensile stress σt	—