Press Fit / Interference Fit Calculator

Calculate interference, contact pressure, axial holding force, torque capacity, and hub stress for press-fit assemblies. This tool is essential for mechanical design, shaft–hub connections, and interference fit engineering.

Press Fit / Interference Fit
Calculator

mm
mm
mm
mm
GPa
ν
μ
Diametral Interference 0 mm
Contact Pressure 0 MPa
Axial Grip Force 0 kN
Grip Torque 0 kN·m
Hub Hoop Stress 0 MPa
Press Fit Result: -
Enter shaft, hub, length and material properties
© CMS TECHNOLOGY

Note: This press fit calculator provides theoretical estimates based on simplified Lamé equations. Actual results may vary depending on material pair, surface finish, lubrication, temperature, geometry, and manufacturing tolerances.

Quick Answer

👉 Key concept:

  • Interference = Shaft OD − Hole ID
  • Interference creates contact pressure, which generates holding force and torque capacity

✔ Example:
Shaft = 50.05 mm
Hole = 50.00 mm
→ Interference = 0.05 mm

Formula (Press Fit Calculation)

1. Diametral Interference

δ = Shaft OD − Hole ID

2. Contact Pressure (Simplified)

p ≈ (δ / D) × (E / (1 − ν²))

  • p = contact pressure (MPa)
  • δ = interference (mm)
  • D = nominal diameter (mm)
  • E = elastic modulus (MPa)
  • ν = Poisson’s ratio

3. Axial Grip Force

F = π × D × L × p × μ

  • F = axial force (N)
  • L = fit length (mm)
  • μ = friction coefficient

4. Torque Capacity

T = F × (D / 2)

5. Hub Hoop Stress (Approx.)

σ ≈ p × (OD² + ID²) / (OD² − ID²)

How to Use This Calculator

  1. Enter shaft outer diameter (OD)
  2. Enter hub bore inner diameter (ID)
  3. Input hub outer diameter (OD)
  4. Enter fit length (mm)
  5. Input material properties:
    • Elastic modulus (E)
    • Poisson’s ratio (ν)
  6. Enter friction coefficient (μ)
  7. Instantly get:
    • Interference
    • Contact pressure
    • Axial force
    • Torque capacity
    • Hub stress

✔ Real-time engineering calculation
✔ Ideal for press-fit design

Common Engineering Uses

1. Shaft–Hub Assembly Design

  • Ensure sufficient holding force without damage

2. Bearing & Gear Mounting

  • Design interference fits for rotating components

3. Torque Transmission

  • Calculate torque capacity without keys or splines

4. Mechanical Safety Verification

  • Prevent excessive stress or material failure

Typical Engineering Values

Parameter Typical Range
Interference 0.01 – 0.05 mm
Friction Coefficient 0.08 – 0.20
Steel Elastic Modulus ~200–210 GPa
Poisson Ratio 0.28 – 0.30

Important Notes

  • This is a simplified analytical model
  • Real-world results depend on:
    • Surface roughness
    • Temperature (thermal expansion)
    • Assembly method (press vs shrink fit)

⚠️ Too much interference → cracking risk
⚠️ Too little interference → slipping risk

Related Calculators

Enhance your engineering workflow:

  • Fits and Tolerances Calculator
  • Hole Size Calculator
  • Material Strength Calculator
  • Torque Calculator

FAQ

What is a press fit?

A press fit is an assembly where parts are joined using interference between mating surfaces.

What is interference fit?

The shaft is intentionally larger than the hole, creating pressure when assembled.

How is holding force generated?

Through friction caused by contact pressure.

What happens if interference is too high?

  • Excess stress
  • Risk of cracking or deformation

What unit is pressure?

Typically MPa.

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CNC Machining Shops

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