Determine tightening torque from target preload using separate thread and bearing friction coefficients.
Set the inputs and start the calculation.
Estimate tightening torque from target preload and thread and bearing friction.
Nominal diameter, pitch, preload, thread and under-head/nut friction and tightening factor define torque.
Friction consumes most tightening torque. Small changes from lubrication, coating or scatter therefore shift preload substantially; torque is not a material-independent constant.
Torque consists of thread torque and bearing friction torque. Friction scatter causes large preload scatter, so measured or supplier friction data matters.
With identical geometry, μ = 0.08 versus μ = 0.16 produces a markedly different torque; torque alone does not guarantee exact preload.
Sources and limits: ISO 16047 covers torque-preload testing; VDI 2230 provides the systematic joint assessment. Use supplier and lubricant data.
Estimate tightening torque from target preload and thread and bearing friction.
Bolt calculations describe a joint through geometry, preload, friction and material limits. Preload clamps the parts; external load, embedding and temperature change the reserve.
Torque consists of thread torque and bearing friction torque. Friction scatter causes large preload scatter, so measured or supplier friction data matters.
Nominal diameter, pitch, preload, thread and under-head/nut friction and tightening factor define torque. Friction consumes most tightening torque. Small changes from lubrication, coating or scatter therefore shift preload substantially; torque is not a material-independent constant.
Enter target preload, thread nominal diameter and pitch, thread and under-head/nut friction coefficients and a tightening factor. Use supplier-stated or measured friction values where possible rather than generic table figures.
With identical geometry, μ = 0.08 versus μ = 0.16 produces a markedly different torque; torque alone does not guarantee exact preload.
Friction consumes most tightening torque. Small changes from lubrication, coating or scatter therefore shift preload substantially; torque is not a material-independent constant. 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.
Force in kN, diameter and pitch in mm, friction coefficients dimensionless, result in N·m.
Setting an assembly target torque for production or maintenance, or estimating how a changed lubricant or coating shifts the required tightening torque.
ISO 16047 covers torque-preload testing; VDI 2230 provides the systematic joint assessment. Use supplier and lubricant data.
Common mistake: Don't assume the same friction value for thread and bearing surface without checking the actual finish – lubricated, coated or galvanized joints can behave differently in each zone. A torque value derived once applies only to the tested friction pairing; changing lubricant requires re-evaluation.
Up to 90% of tightening torque is consumed purely by friction in the thread and under the head or nut; only a small remainder actually produces the preload.
VDI 2230 and ISO 16047 give reference values for common surfaces, but they should be confirmed by an actual torque-preload test of the parts used when preload is safety-relevant.
No. Friction scatter causes preload scatter of often ±25% or more even at exactly the specified torque; torque-controlled tightening is an approximate method.
Target preload, thread size, bearing diameter, and separate friction coefficients determine required tightening torque.
Friction consumes most tightening torque. A calculated nominal value is meaningful only when surface, lubrication, and bearing geometry are controlled.
Use test data or qualified supplier documentation, not an undifferentiated table value.
One nominal torque does not represent tool and friction variation.
Clamp load, embedding loss, service load, and fatigue belong in a complete joint assessment.
Testing torque/preload behaviour and separated friction coefficients.
Systematic design of highly stressed single-bolt joints.
Requirements and calibration for hand torque tools.