Plain bearings and sliding bushings

Frequently asked questions — Plain Bearings

• How do you choose between a plain bearing and a conventional rolling bearing?

  The plain bearing, or sliding bearing, is an alternative to rolling-element bearings for the rotational guidance of a shaft. It eliminates the presence of rolling elements, cages and seals, allowing minimal space requirements. This choice is justified when the application requires increased shock resistance and high tolerance to environmental contamination, unlike rolling bearings, which are sensitive to these conditions.
• What is the difference between sintered bronze bushings and composite models?

  Sintered bronze, compliant with the DIN ISO 4379 standard, is impregnated with oil to provide lifetime lubrication over several thousand hours without maintenance. Conversely, steel-bronze-PTFE composite bushings of the DU, DX or KX type offer significantly higher load capacity. This structure combines the rigidity of steel, the thermal dissipation of bronze and the low coefficient of friction of filled PTFE for superior performance.
• Why choose an engineering polymer bushing?

  Bushings made from engineering polymers such as POM, PA66, PEEK or polyimide are selected for their light weight and resistance to chemicals. They offer the food-grade compatibility essential in certain industrial environments. Although their load capacities and operating speeds are more limited than metallic versions, they provide a suitable solution for specific applications where corrosion or purity are determining factors.
• What is the PV parameter and how is it used to size a plain bearing?

  The PV value is the central sizing parameter, calculated as the product of pressure P in MPa and linear velocity V in m/s. It defines the operating limits of each technology. For example, sintered bronze withstands a PV of approximately 1.8 N/mm² · m/s, whereas a DU-type composite bushing can reach 3.5. Compliance with this PV threshold is essential to ensure the longevity of the sliding contact.
• When should solid CuSn8 bronze bushings be used?

  Solid CuSn8 bronze bushings, compliant with the DIN EN 12420 standard, are recommended for heavy-duty applications requiring regular greasing. Unlike self-lubricating models, they incorporate dedicated grease grooves to channel the lubricant to the contact zone. This type of bearing is the technical reference whenever load constraints exceed the capabilities of sintered or composite materials.