A press fit (interference fit) is an assembly where the shaft diameter is larger than the hub bore by the interference δ. The elastic deformation creates a contact pressure that transmits torque and axial force.

How do I calculate the holding torque?

Torque capacity T = μ × p × A × r_i where μ is friction coefficient, p is interface pressure, A is contact area, and r_i is interface radius. Typical μ for steel: 0.12–0.20.

What is a shrink fit?

A shrink fit heats the hub (or cools the shaft with liquid nitrogen) to ease assembly, then lets it cool to create the interference. Used for tight fits that would require excessive press force.

Press Fit Interface Stress Calculator

Calculate contact pressure and hoop stress in press-fit (interference fit) assemblies. Input diametral interference δ, hub and shaft dimensions, and material properties to find assembly and holding force.

2D stress state at a point. All stresses in MPa.

σx — Normal Stress X (MPa)

σy — Normal Stress Y (MPa)

τxy — Shear Stress (MPa)

⚙ Mechanical Note: Results are based on standard textbook formulas and ISO/AASHTO references. Always verify critical designs with applicable codes (ISO 898, AASHTO 1993, AISC, Eurocode 3) and a qualified engineer.

How to Use

Enter the values for the patient or scenario you are assessing. Calculate contact pressure and hoop stress in press-fit (interference fit) assemblies. Input diametral interference δ, hub and shaft dimensions, and material properties to find assembly and holding force. Use the press fit stress result to inform your clinical assessment.

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Press Fit Interface Stress Calculator

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Frequently Asked Questions

What is a press fit?

How do I calculate the holding torque?

What is a shrink fit?