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Interference Fit Spec Table
Interference Fit KS Specifications — 6 sizes
KS B 0401
An interference fit where the shaft is larger than the hole, requiring press-fitting. Used for permanent mounting of bearings, bushings, and gears.
Practical Notes
- For shrink fitting, calculate heating temperature considering thermal expansion coefficients. Aluminum housing expands 2× more than steel — avoid overheating.
- Check for deformation after press fitting. Thin-walled bushings and housings lose roundness with excessive interference.
Selection Guide
Shaft larger than hole; assembled by hydraulic press or shrink fit (heating). Common fits: H7/p6 (light press), H7/r6 (medium), H7/s6 (heavy). For permanent fixing — bearing inner rings, gear-shaft press fits. Excessive interference can cause deformation or cracking; calculation is essential.
KSInterference Fit
6 sizes| Fit | Hole Tol | Shaft Tol | Type | Clearance | Use |
|---|---|---|---|---|---|
| H7/n6 | H7 | n6 | Interference | 0~0.033 | Bush, Bearing |
| H7/p6 | H7 | p6 | Interference | 0.008~0.042 | Pin, BushPermanentStatic |
| H7/r6 | H7 | r6 | Interference | 0.015~0.050 | Light PartsPress-fit |
| H7/s6 | H7 | s6 | Interference | 0.028~0.063 | Heavy LoadPress-fit |
| N7/h6 | N7 | h6 | Interference | 0~0.029 | BushPress-fit |
| P7/h6 | P7 | h6 | Interference | 0.008~0.037 | PermanentStatic |
Key Features
- Shaft tolerance zones p–z + hole zone H; always guarantees negative clearance (interference)
- Representative fits: H7/p6 (light press), H7/r6 (medium press), H7/s6 (heavy press)
- Assembled by hydraulic press or shrink fit (heat expansion); capable of transmitting shear torque
Key Applications
Gear-shaft press fit, bearing inner ring fixing, bushing press fit, flywheel hubs, valve seat insertion
FAQ
How to calculate press-fit force?
Press force (N) ≈ π × d × L × μ × p. d=contact diameter, L=contact length, μ=friction coefficient (~0.12 steel-steel), p=contact pressure (from interference). Use Lamé equations for precise calculation.