A rigid coupling joins two aligned shafts so they rotate together without an intentional flexible element. The selected calculator is narrower: it estimates a lumped ideal friction limit for one limiting smooth-bore split-clamp interface.
Rigid Coupling Interactive Calculator
Explore a lumped ideal friction limit for one selected smooth-bore split-clamp interface.
Equation Used
- Entered clamp force is total effective normal force at one limiting shaft interface.
- Friction coefficient is a selected constant and effective radius is half the shaft diameter.
- The two shafts are aligned and the coupling does not slip below the idealized limit.
- Screw preload conversion, pressure distribution, fit, keys, strength, fatigue, speed, dynamics and ratings are excluded.
The secondary figure uses the same selected interface force, friction coefficient, shaft diameter and applied torque.
How the selected split-clamp rigid coupling works
A split sleeve surrounds the ends of two aligned shafts. Tightening its clamp screws closes the split and develops contact pressure on the shafts, allowing torque to pass by friction. The coupling body keeps the shafts in one fixed rotational relationship.
The calculator defines clamp force as total effective normal force at one limiting shaft-to-coupling interface. That lumped quantity is not screw tension, tightening torque or catalog torque rating.
What this calculator demonstrates
Select total effective interface normal force, an assumed friction coefficient, shaft diameter and applied torque. The calculator returns ideal friction torque limit, friction capacity ratio, ideal torque margin and utilization.
It does not convert screw tightening torque to preload or contact pressure. It also excludes fit, surface condition changes, keys, set screws, coupling-body and shaft strength, fatigue, alignment, speed, temperature, installation and manufacturer ratings.
Selected lumped friction model
Let F be total effective normal force at the selected limiting interface, μ the assumed constant friction coefficient and d the shaft diameter. With effective radius r = d/2, ideal friction torque limit is Tf = μFr = μFd/2.
For applied torque T, capacity ratio C = Tf/T, ideal margin M = Tf − T and utilization U = 100T/Tf. C is not a design safety factor or catalog service factor.
Default selected example
With total effective normal force F = 2,000 N, μ = 0.18, d = 12 mm and applied torque 1.5 N·m, the ideal friction limit is 2.16 N·m. Capacity ratio is 1.44, ideal margin is 0.66 N·m and utilization is about 69%.
This arithmetic does not approve a coupling or establish the clamp force produced by any screw setting.
Scope and correction boundary
Stafford identifies rigid clamp couplings as connectors for aligned shafts and distinguishes smooth-bore, keyed and other constructions. Lovejoy likewise states that rigid sleeve couplings require maintained shaft alignment and proper bearing support. Actual products are selected from manufacturer torque, bore, speed and installation data.
The removed article switched between a shaft torsion equation and a clamp-friction calculator, then supplied universal fits, alignment limits, lives, prices and diagnoses. The replacement consistently covers only the selected smooth-bore friction interface model.
Questions
Is entered clamp force the same as screw preload?
No. It is the selected total effective normal force at one shaft interface. Relating screw torque or tension to interface pressure requires coupling geometry, fastener data and manufacturer instructions.
Is the capacity ratio a safety factor?
No. It is only ideal friction limit divided by applied torque in this lumped model.
Does a rigid coupling accommodate shaft misalignment?
A rigid coupling has no intentional flexible element. Align and support the shafts within the exact product's instructions and connected-equipment requirements.
Can this model be used for keyed or set-screw couplings?
No. Keys, set screws, interference fits and other torque paths require different models and product data.
Primary technical references
- Stafford Manufacturing, Rigid Shaft Couplings — manufacturer overview of aligned-shaft connection, clamp styles and inability of rigid designs to compensate for misalignment.
- Stafford Manufacturing, Rigid Coupling Catalog — distinguishes smooth-bore, keyed, one-piece and two-piece clamp constructions and product torque capabilities.
- Lovejoy, Rigid Sleeve Coupling — manufacturer scope requiring maintained alignment and proper bearing support.
- Lovejoy, Rigid Coupling Installation Instructions — product-specific alignment, tightening and inspection requirements.
Building or designing a mechanism like this?
Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.
