Calculate tensile, torsional, and von Mises equivalent stress from preload and thread torque.
Set the inputs and start the calculation.
The calculator forms the bolt stress state during tightening: tensile stress from the preload, torsional stress from the thread torque, and the resulting equivalent stress.
Nominal diameter, pitch (giving Aₛ and d₃ per ISO 724), ISO 898-1 property class, assembly preload F_M and thread torque M_G (for example from the tightening-torque calculator).
Tensile stress area is smaller than nominal area because the thread root carries the load. Transverse force adds shear; only the combination shows the actual margin.
σ_M = F_M/Aₛ; τ_M = M_G/W_P with W_P = π·d₃³/16 (conservative choice d₀ = d_i,min from VDI 2230-1, R8); σ_red,M = √(σ_M² + 3·τ_M²). Utilization relates σ_red,M to the proof stress S_p of the property class.
M10×1.5, 8.8, F_M = 25 kN, M_G = 21.8 N·m: σ_M ≈ 431 MPa, τ_M ≈ 204 MPa, σ_red,M ≈ 557 MPa, utilization ≈ 96% of S_p = 580 MPa.
Sources and limits: ISO 724 gives d₂, d₃ and Aₛ; ISO 898-1 gives S_p; VDI 2230-1:2015 clause 5.5.1 and R7/R8 describe the assembly stress check. External working loads, embedding and fatigue belong to the complete joint assessment.
The calculator forms the bolt stress state during tightening: tensile stress from the preload, torsional stress from the thread torque, and the resulting equivalent stress.
Bolt calculations describe a joint through geometry, preload, friction and material limits. Preload clamps the parts; external load, embedding and temperature change the reserve.
σ_M = F_M/Aₛ; τ_M = M_G/W_P with W_P = π·d₃³/16 (conservative choice d₀ = d_i,min from VDI 2230-1, R8); σ_red,M = √(σ_M² + 3·τ_M²). Utilization relates σ_red,M to the proof stress S_p of the property class.
Nominal diameter, pitch (giving Aₛ and d₃ per ISO 724), ISO 898-1 property class, assembly preload F_M and thread torque M_G (for example from the tightening-torque calculator). Tensile stress area is smaller than nominal area because the thread root carries the load. Transverse force adds shear; only the combination shows the actual margin.
Enter nominal diameter and pitch, the property class, the assembly preload F_M and the thread torque M_G. The thread torque is the friction-plus-pitch share inside the thread, not the whole tightening torque; the tightening-torque calculator reports it separately.
M10×1.5, 8.8, F_M = 25 kN, M_G = 21.8 N·m: σ_M ≈ 431 MPa, τ_M ≈ 204 MPa, σ_red,M ≈ 557 MPa, utilization ≈ 96% of S_p = 580 MPa.
Tensile stress area is smaller than nominal area because the thread root carries the load. Transverse force adds shear; only the combination shows the actual margin. A passing result means only that the selected model stays within the entered limits. Tightening scatter and real contact surfaces may govern residual clamp force.
Forces in N or kN, torques in N·m, stresses in MPa; Aₛ and W_P are formed internally in mm² and mm³ from ISO 724.
Checking how far a planned preload utilizes the bolt during tightening, for example when choosing a property class or classifying an assembly preload level (VDI 2230 recommends about 90% of R_p0.2 for assembly).
ISO 724 gives d₂, d₃ and Aₛ; ISO 898-1 gives S_p; VDI 2230-1:2015 clause 5.5.1 and R7/R8 describe the assembly stress check. External working loads, embedding and fatigue belong to the complete joint assessment.
Common mistake: Do not enter the whole tightening torque as thread torque – the under-head friction share creates no torsion in the shank. The equivalent stress describes the assembly state; it replaces neither the working-load check nor the assessment of embedding and fatigue.
VDI 2230-1 allows both the stress diameter dₛ and the minimum minor diameter d_i,min for W_P. The calculator uses d₃ and is therefore on the safe side; with dₛ, τ_M would be about 15% lower.
From the tightening-torque calculator, which splits the tightening torque into thread and under-head friction shares, or from a measurement per ISO 16047.
No. A real joint additionally needs working loads, embedding behavior, fatigue strength, surface pressure and the clamped parts checked per VDI 2230.
Preload, thread geometry, and thread torque produce tensile, torsional, and equivalent stress plus utilization.
Equivalent stress represents local tightening stress. External axial load, bending, transverse load, notch effects, and fatigue are not included.
Torsional stress uses torque acting in the thread, not total tightening torque.
Determine load sharing between bolt and clamped parts from their compliances.
Alternating load and possible joint slip require separate checks.
Complete assembly, service, fatigue, and clamp-load verification.
Mechanical properties and proof stresses for carbon and alloy steel bolts.
Account for capacity of the mating nut or internal thread.