SKF
Selecting Bearing Size (Bushings)
Sizing bushings and thrust washers involves calculating the maximum specific bearing pressure (p = F/A) and comparing it to the material’s static and dynamic load limits. For dynamic applications, the pv value must also be within the material’s permissible range. SKF provides formulas and pre-calculated size tables based on shaft diameter and expected load. Proper sizing avoids plastic deformation of the liner and excessive wear. For thin-walled composite bushings in particular, the support from the housing is crucial, and SKF’s load ratings assume a rigid, properly toleranced housing.
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Specific Bearing Pressure p = F/A
Must be below the material’s static and dynamic limits.
Dynamic pV = p × V
Must stay below the material’s pV limit to avoid overheating.
Aspect Ratio Influence
Longer bushing length reduces pressure but increases edge‑loading risk.
Wall Thickness Options
Thicker walls carry more load but require more housing space.
Clearance Selection
Recommended running clearance based on bushing material and operating temperature.
Standard Size Catalogues
Pre‑calculated load ratings for common shaft diameters.
How to Calculate pV for Oscillating Motion
For a bushing that oscillates through an angle θ at frequency f, the average sliding speed V = (θ/180) × π × d × f. This value is used in the pV calculation. SKF’s engineering handbook includes a dedicated section for oscillating applications to prevent the common error of using full‑rotation speed formulas.
Preventing Liner Squeeze‑Out Under High Edge Loads
If the shaft tilts and the bushing length‑to‑diameter ratio exceeds 2:1, edge pressure can squeeze the soft liner out. SKF’s sizing tool flags these conditions and recommends either a shorter bushing, a harder material, or a crowned bushing that relieves edge contact.