Calculation
Tnom = n·π·DF·μ·FK/(2·C)
More bolts, clamp force, diameter or friction increase capacity linearly.
Roloff/Matek Gl. (12.38)
Split clamp-hub torque
More bolts, clamp force, diameter or friction increase capacity linearly.
MINTSI
02
Result
Select a target and calculate.
Understand the inputs
- Nominal torque Tnom — Capacity after the entered duty and safety factor.
- Number of bolts n — Equally loaded clamp bolts.
- Joint diameter DF — Shaft diameter at the clamped interface.
- Static friction coefficient μ — Static coefficient of the shaft-hub interface.
- Clamp force per bolt FK — Effective clamp force per bolt, not merely tightening torque.
- Combined factor C — Product of application factor and friction safety; model assumes uniform pressure K=1.
Example
n=2, D=50 mm, μ=0.15, FK=20 kN and C=1.5 give 314 N·m.
Assumptions and limits
Split hub with uniform pressure K=1; verify bolt preload and interface pressure separately.
Understand Split clamp-hub torque
Split clamp-hub torque is a focused preliminary calculation based on Roloff/Matek. The calculator rearranges the closed-form relationship for every included quantity and deliberately separates this result from a complete component verification.
What does this quantity describe?
Equation 12.38 is rearranged to obtain nominal torque from bolt count, clamp force, joint diameter, static friction and a combined factor; K=1 represents uniform pressure.
Formula and variables
Tnom = n·π·DF·μ·FK/(2·C)
Tnenn = n π DF μ FK / (2 KA SH)
| Symbol / input | Meaning |
|---|---|
| Nominal torque Tnom | Capacity after the entered duty and safety factor. |
| Number of bolts n | Equally loaded clamp bolts. |
| Joint diameter DF | Shaft diameter at the clamped interface. |
| Static friction coefficient μ | Static coefficient of the shaft-hub interface. |
| Clamp force per bolt FK | Effective clamp force per bolt, not merely tightening torque. |
| Combined factor C | Product of application factor and friction safety; model assumes uniform pressure K=1. |
Choose the inputs correctly
n counts active bolts, FK is effective clamp force per bolt, DF shaft diameter, μ static friction and C=KA·SH combines application and friction-safety factors.
How to use the calculator
Select the target, enter all remaining quantities for the actual component, and verify the units. Then compare the result with the stated model limits and with the required strength, safety and operating checks.
Worked example
2 bolts, 50 mm, μ=0.15, 20 kN each and C=1.5 give 314 N·m.
Understand the result and units
The result decreases in proportion to C. Tightening torque must not be entered directly as clamp force.
The calculator converts internally to coherent SI units. Length, force, torque, stress and angle may therefore use the offered units; dimensionless factors are entered as decimals.
What is taken from Roloff/Matek
Only the closed-form relationship from Kapitel 12.3.4, Gleichung (12.38) is used. Tabulated data, material limits and detailed design checks are not silently added; they remain explicit inputs or are expressly outside the model.
Typical applications
Split clamp-hub torque supports option comparison, plausibility checks and early sizing within its machine-element cluster. Releasing a design requires the additional checks described in the cited chapter.
Assumptions, limits and common mistakes
Only for a split hub with uniform pressure K=1; separately verify assembly preload and allowable interface pressure using equation 12.39.
Common mistake: Typical errors are misreading the effective length or force, entering percentages instead of decimals, and treating a preliminary result as a complete verification. In particular: Only for a split hub with uniform pressure K=1; separately verify assembly preload and allowable interface pressure using equation 12.39.
Frequently asked questions
Is Split clamp-hub torque a complete strength verification?
No. Only for a split hub with uniform pressure K=1; separately verify assembly preload and allowable interface pressure using equation 12.39.
Where do the equation and validity limits come from?
Roloff/Matek, Machine Elements, Kapitel 12.3.4, Gleichung (12.38); the local 21st edition was cross-checked against the available 24th edition.
Can I order the calculated value directly as a nominal size?
Only after matching it to available standard or manufacturer series and completing the additional safety, material and operating checks.