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Metric Thread & Bolt Calculator

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1. Thread & Joint Configuration

THREAD
Preload
FRICTION / TIGHTENING
mm
Internal thread
MPa
mm
M10 × 1.5
6g / 6H · ISO 898-1
8.8
Rp / Re = 640 MPa

ISO Metric Thread Geometry

Nominal diameter dØ10 mm
Pitch diameter d₂Ø9.026 mm
Minor diameter d₃Ø8.16 mm
Stress area As57.99 mm²
Helix angle at d₂3.03°

Machining

Indicative tap drill
Ø8.5 mm

d − P estimate; final drill depends on tap, material and target thread percentage.

Clearance holes — ISO 273
Fine seriesØ10.5 mm
Medium seriesØ11 mm
Large seriesØ12 mm

Bolt Preload

Proof stress Sp580 MPa
Proof load Fp33.63 kN
Target preload FM23.54 kN
Target70 %

Tightening Estimate

Thread torque MG22.99 N·m
Bearing torque MK21.42 N·m
Total torque MA44.42 N·m
Equivalent K factor0.189

Bolt Stress During Tightening

Axial stress σOK
406 MPa
Torsional stress τOK
215.55 MPa
Equivalent stress σVMOK
551.56 MPa
Utilisation vs ReOK
86 %
σVM / Re = 0.862 · torsion based on thread torque MG, not total wrench torque MA.

Preliminary Internal Thread Check

Available engagementOK
10 mm
Rule-of-thumb referenceOK
10 mm
Preliminary stripping capacityCHECK
25.52 kN
Preliminary factor vs FMCHECK
1.08
τallow180 MPa
Aτ approx.141.78 mm²
Engaged threads6.7
MaterialStructural / carbon steel

The stripping calculation is a preliminary screening model, not a complete normative thread-stripping calculation. Load distribution between engaged threads is non-uniform and both male and female thread strength must be considered in a final design.

Friction Sensitivity

Low friction36.63 N·m
Nominal44.42 N·m
High friction52.21 N·m

Sensitivity shown for ±20% change in both friction coefficients while maintaining the same target preload. Real torque-controlled tightening also produces preload scatter.

2D THREADED JOINT

Ø11.0M10 × 1.5Le = 10 mmd = 10 mm | d₂ = 9.026 mm | d₃ = 8.16 mm

Engineering Notes

• Preliminary calculation only. This is not a complete VDI 2230 analysis and does not replace verification of applicable standards, tolerances, joint stiffness, external loads, fatigue and the actual tightening method.

• The displayed tolerance classes identify the intended thread fit but this version does not calculate ISO 965 limit deviations and limit diameters.

• The d − P tap-drill value is a workshop estimate, not a normative drill diameter.

• ISO 273 clearance-hole values are shown as fine, medium and coarse series. The calculator does not automatically assign H12/H13/H14 tolerance classes to those series.

• Dkm must be based on the real bearing geometry of the bolt head, nut or washer for a refined tightening calculation.

• Friction coefficients are major uncertainty sources. Lubrication, coating, surface condition and repeated tightening can strongly change preload obtained from a given torque.

• ISO 898-1 defines mechanical properties of steel fasteners; it does not specify torque/clamp-force performance. The tightening torque shown here is an engineering estimate based on geometry, target preload and friction.

• Preliminary internal-thread stripping margin is low. Increase engagement, improve tapped-part material or perform a detailed thread-strength calculation.

Engineering report

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Formulas & methodology

  • ISO metric basic thread geometry is generated from nominal diameter and pitch using the implemented profile relationships.
  • Tensile stress area is estimated from the effective thread diameter relationship used by the calculator.
  • Target preload = selected utilization × the implemented bolt proof/load basis.
  • Tightening torque = thread-friction torque + under-head/bearing friction torque.
  • Thread stripping capacity is estimated from engagement length, thread geometry and allowable internal-thread shear stress.

Engineering basis & standards

  • Metric thread geometry follows ISO metric thread concepts; clearance-hole guidance is based on ISO 273 series values implemented in the tool.
  • Carbon/alloy steel bolt property classes use ISO 898-1 context, while stainless fastener context is separated under ISO 3506-1 where applicable.
  • Torque/preload prediction is an engineering estimate; ISO 898-1 does not itself define a tightening-torque relationship.

Assumptions

  • Friction coefficients are effective engineering inputs and are assumed representative of the real lubrication, coating and surface condition.
  • The joint is treated as a conventional concentric bolted joint without a full joint-stiffness or external-load distribution model.
  • Internal-thread shear capacity uses the selected allowable shear stress and engagement model.

Warnings / limits

  • Torque is an indirect and scatter-sensitive way of controlling preload. Critical joints may require torque-angle, yield-controlled or direct-tension methods.
  • Check fatigue, separation/slip, bearing pressure, joint stiffness, relaxation and service temperature for production designs.
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Related engineering reading

Bolt preload vs torque →M10 bolt torque guide →ISO 898-1 reference →ISO 273 reference →