Bolt Torque & Preload Calculator (VDI 2230)

Tightening torque and preload analysis with VDI 2230 nut factor K1+K2+K3. Computes thread vs bearing face torque split and yield utilization margin.

Tightening Torque
83.1N·m
Useful: 9.9 N·m
Preload Force
35.4kN
Slip Limit: 7.1 kN
Nut factor K
0.196
K₁=0.023 K₂=0.073 K₃=0.099
Sp / Sy Limit
600MPa
σeq = 497 MPa · n = 1.29
Structural Integrity · σz=420 MPa · τ=153 MPa · σeq=497 MPa · As=84.3 mm²
M12 · 8.8L=50mm · Preload FM = 35.4 kN
Rötscher Cone (2α=60°)σeq 497 MPa8.8MA = 83.1 N·mFM 35.4 kNFM 35.4 kNL = 50 mmlK = 35.2 mmk=7.5m=10.8
HOVER PARTS TO DEEP-DIVE DIMENSIONS
von Mises Stress
σeq = 497 MPa
0Sy 640 MPa
Tensile Stress
σz = 420 MPa
F0: 35406 NRm 800
Torsion Shear
τ = 153 MPa
M2: 31.1 N·mτy: 371
Yield Safety
n = 1.29
Güvenli (Safe)Min 1.2
Formula

MA = K · F₀ · d · 10⁻³ F₀ = v · As · Sp K = K₁+K₂+K₃ σeq = √(σz² + 3τ²)

VDI 2230 simplified torque + ISO 68-1 / 965 thread geometry.

VDI 2230ISO 898-1ISO 68-1 / 965ISO 273ISO 4017ANSI B1.20.1ISO 228-1
Assumptions
  • •Friction μG/μK treated constant; real joints scatter with finish & lube.
  • •dw ≈ 0.95·e under-head bearing OD (no washer) or standard washer face.
  • •Geometry from ISO 68-1 formulas + ISO 4017 head sizes + ASME B1.20.1 pipe standards.
Academy
▸Formula · assumptions · worked example(VDI 2230 Part 1:2015 · DIN EN ISO 898-1 · ISO 68-1 / ISO 273)

Formula

M_A = F_M \left( 0.16 \cdot P + 0.58 \cdot \mu_G \cdot d_2 + 0.50 \cdot \mu_K \cdot d_w \right)

Tightening torque calculation per VDI 2230-1 nut factor and multi-zone friction method. FM is target preload, P is pitch, d2 is pitch diameter, and dw is bearing face diameter.

Assumptions

  • · Friction coefficients (thread μG & bearing face μK) dominate torque split — verify lubrication state
  • · Target preload FM engineered to utilize 90% of fastener material yield strength (Rp0.2)
  • · Account for embedment relaxation losses and thermal expansion differential in critical joint stacks
Bolt torque guide →
VDI 2230-1:2015 / ISO 898-1 / ISO 68-1

Metric Bolt Joint Tightening Verification (M12 × 8.8)

STATUS: PASS(+28.9% yield reserve (FoS = 1.29))

Calibrated tightening torque and preload clamp force analysis under standard friction lubrication (μ = 0.14) with proof stress utilization.

1. Inputs & Boundary Parameters (Girdiler)
Nominal diameter d12.00 mm
Thread pitch P1.75 mm
Property classGrade 8.8 ISO 898-1
Yield strength Sy640.0 MPa
Proof strength Sp600.0 MPa
Tensile stress area As84.3 mm²
Core diameter d310.11 mm
Thread friction μG0.140 [-]
Bearing face friction μK0.140 [-]
Target yield util. ν0.700 (70% Sp)
2. Applied Governing Equations & Standard Clauses (Bağıntılar & Norm Maddesi)
Target Preload FM: FM = ν · Sp · As
VDI 2230 / ISO 898-1
Tightening Torque MA: MA = (K1 + K2 + K3) · FM · d
VDI 2230 Torque Engine
Torsional Shear Stress τ: τ = (M2 · 1000) / Wp [Wp = (π · d3³) / 16]
VDI 2230 Clause 5.5
von Mises Equivalent Stress: σeq = √(σz² + 3 · τ²) ≤ Sy
VDI 2230 / DIN EN ISO 898-1
3. Intermediate Calculation Stages (Ara Değerler)
Axial tensile stress σzσz = FM / As = 35400 / 84.3
420.0 MPa
Torsional shear stress τPolar modulus Wp = 346.4 mm³
153.0 MPa
Preload clamp force FMFM = 0.70 · 600 · 84.3 · 10⁻³
35.4 kN
Tightening torque MANut factor K = 0.196
83.1 N·m
4. Engineering Verification Result & Limit Threshold (Sonuç + Sınır)PASS
Equivalent von Mises Stress & Tightening Torque: σeq = 497.0 MPa | MA = 83.1 N·m | FM = 35.4 kN
Acceptance limit: σeq ≤ 640.0 MPa (Sy) | FoS = 1.29 ≥ 1.05