Press Fit Calculator

Summary

Enter shaft/hole diameters, material properties, contact length, and friction coefficient to get contact pressure, press force, and torque capacity.

How it works

1. Interference δ is the difference between shaft diameter and hole diameter (shaft larger = positive interference).
2. Contact pressure is derived from the Lame thick-cylinder equations applied to the hub and shaft.
3. Axial press force equals friction coefficient × contact pressure × π × shaft diameter × contact length.
4. Torque capacity equals friction coefficient × contact pressure × π × shaft radius² × 2 × contact length.
5. Unit toggle converts all inputs and outputs between mm/MPa and inch/psi without re-entry.

Use cases

• Verify that a chosen shaft/hub diameter pair produces adequate torque capacity for a gear or pulley assembly.
• Estimate the press force required for an assembly press to assemble a bearing or bushing.
• Check whether an interference fit will yield the hub material during assembly.
• Compare metric and imperial fit tolerances when working across unit systems.
• Design shrink-fit assemblies where the hub is heated to expand before slipping over the shaft.

Frequently Asked Questions