Bolt Torque & Preload Calculator (VDI 2230)

VDI 2230ISO 898-1ISO 4017 / ISO 4762 geometry

Tightening torque and preload analysis with VDI 2230 nut factor K1+K2+K3. Uses the same ISO production dimensions as the thread geometry module.

Bolt Torque

Formula

T = K × F × d

K is the nut factor (≈ K1+K2+K3 per VDI 2230 practice). F = preload, d = nominal diameter.

VDI 2230ISO 898-1ISO 4017 / ISO 4762 geometry

Assumptions & limits

•Friction coefficients dominate K — verify lubrication state
•Preload target must leave margin under proof load
•Results are for preliminary joint design, not a substitute for full VDI analysis on critical joints

Bolt torque guide

Worked example — M12 × 8.8

→Metric coarse M12 (d = 12 mm)
→Property class 8.8
→μ_thread = μ_head = 0.15 (dry-ish / lightly oiled)
→Yield utilization ≈ 90%

Engine computes K = K1+K2+K3, target preload Fm from yield utilization, then tightening torque MA = K × Fm × d. Open the workbench to see live MA, Fm, and torque split.

Changing lubrication can move MA by 30%+ at the same preload target — always state μ assumptions on drawings.

Load M12 · 8.8 in calculator