⚡ Press Fit Calculator

Calculate interference fit contact pressure and required press force for shaft and hub assemblies. Based on Lame's equations for thick-walled cylinders.

Geometry

Shaft OD (in)

Hub Bore (in)

Hub OD (in)

Engagement Length (in)

Material (same for shaft & hub)

Elastic Modulus (psi)

Friction Coefficient

Assumes: Solid shaft, same material for shaft and hub, room temperature assembly.
Contact Pressure: P = δ / (d × (C_hub + C_shaft) / E)
Press Force: F = π × d × L × P × μ
Typical μ: Steel/steel dry ≈ 0.12–0.15, lubricated ≈ 0.05–0.08

Why Press Fit Calculations Matter

Press fits (interference fits) hold parts together through friction alone — no fasteners, no adhesives. The interference between shaft and bore creates radial stress that locks the assembly. Too little interference and it slips; too much and you crack the hub or gall the shaft.

Interference is the difference between shaft OD and bore ID — typical values range from 0.001 to 0.003 inches per inch of diameter
Insertion force depends on interference, contact length, material properties, and surface finish — rougher surfaces increase friction dramatically
Thermal expansion is your friend: heating the hub 200-300 degrees F or cooling the shaft with dry ice makes assembly easy and avoids galling

⚡ Press Fit Calculator

Why Press Fit Calculations Matter

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