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Oil Free Bushings, Washers

Lubrication-free bushings/washers are bearing components that don't require lubricating oil. Since bearings usually receive a lot of frictional resistance that generates heat, lubricants such as oil or grease are used to prevent the seizing or abnormal wear that this frictional heat could otherwise cause. Lubrication-free bushings don't need lubricating oil because the bearing body has a lubricating structure made possible by lubricating oil in the bearing body, or by embedded solid lubricant or the like. Lubrication-free washers are washers that can receive thrust loads, and have the same lubricating structure as lubrication-free bushings. They are usually used together with lubrication-free bushings. Lubrication-free bushings and washers are both highly effective under conditions where using lubricants is difficult due to the operating environment or structure. They also greatly reduce maintenance costs by eliminating the need for regular lubrication, and enabling stable operation over long periods.

Load Handling Characteristics

Oil Free Bushings are designed to withstand radial loads, while Oil Free Washers are capable of handling thrust loads. Load capacity is defined by the maximum allowable surface pressure, which is calculated using the projected bearing area (bushing inner diameter × bushing length). For reliable operation, surface pressure (P), sliding speed (V), and the PV value must remain within specified limits.

Material Types and Performance

Oil Free Bushings and Washers are available in multiple material variants to suit different operating environments:

  • Copper Alloy Type: Offers excellent wear resistance and corrosion resistance, suitable for general industrial applications.
  • Dry Type (PTFE Resin Layer): Maintains lubrication performance even in wet or water-exposed environments.
  • Bronze Type: Porous structure allows consistent lubrication, ideal for short-stroke or oscillating motion.
  • Polyacetal Resin Type: Copper-free specification suitable for non-copper environments and lightweight applications.

Fixing and Installation Methods

Depending on the product, Oil Free Bushings can be installed using:

  • Press-Fit: Recommended for most applications; chamfered housing and light lubrication on the outer surface are advised.
  • Set Screw Fixing: Prevents rotation and axial movement.
  • Adhesive Fixing: Used where mechanical fixing is restricted.

Proper fixing ensures stability, prevents rotation, and extends service life.

Flanged vs. Thrust Type Bushings

Although similar in appearance, flanged type and thrust type bushings differ in function. Flanged types do not contain lubricant on the flange surface and are used mainly for radial loads. Thrust types include lubricant on the flange surface, allowing them to support both radial and thrust loads simultaneously.

Applications

Oil Free Bushings and Washers are widely used in:

  • Industrial automation equipment
  • Sliding and linear motion mechanisms
  • Door and gate systems
  • Jigs, fixtures, and machine assemblies
  • Applications where lubrication is difficult or prohibited
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