Flanged Bronze Bushings BP25 — C22 to C60

BP25 sintered bronze is manufactured by compacting bronze powder and sintering it below the melting point, which fuses the particles while deliberately leaving a network of interconnected pores — typically on the order of 20–25% of the volume in this class of material. After sintering, the bushings are vacuum-impregnated with a low-viscosity mineral oil that fills this porosity, so the finished part behaves as a self-contained bearing and lubricant reservoir in one component.

When the shaft rotates, frictional heat and the pressure of the developing hydrodynamic film draw oil out of the pores and into the running clearance, establishing a lubricating film between shaft and bore. As the material warms, the oil's thermal expansion assists this release; when motion stops and the bearing cools, capillary action pulls the oil back into the matrix. The result is a self-regulating cycle that keeps the interface lubricated during running and retains the oil at rest, allowing genuinely maintenance-free, dry-running operation within the typical limits of the material class. On a flanged bushing this same mechanism lubricates both the cylindrical bore and the flange face, so the collar can accept light axial sliding as well as locating the bearing.

BP25 flanged bushings are designed for a press (interference) fit into a prepared housing bore. The porous structure means the running clearance is created after fitting: pressing into a correctly sized housing closes the outside diameter slightly, and the finished bore must be checked for the intended shaft clearance rather than relying on the free dimension.

• Use a clean, chamfered housing bore machined to the recommended interference for sintered bushes; a lead-in chamfer helps the bearing start square.
• Press using a flat, piloted mandrel that bears on the flange face and the bore end together, applying force squarely and axially so the collar seats flush against the housing face without cocking.
• Never hammer directly on the bearing or use a drift on the running surface — impact loads can distort the bore and burnish the pores closed, reducing oil release.
• Avoid reaming, honing or machining the bore after fitting; cutting or heavy abrasion smears metal across the surface and seals the porosity, which impairs self-lubrication.
• Keep the parts clean and oil-free of solvents that could leach the impregnated oil; if the surface looks dry after long storage, a wipe of compatible mineral oil restores the film without harming the bearing.
• After pressing, verify the assembled bore diameter and confirm the shaft slides with the correct clearance before final assembly.

Choose a BP25 flanged bushing when the mechanism needs both radial support and axial location in a single component — the integral collar replaces a separate thrust washer and locates the bearing against a housing face. If your point sees purely radial load and needs no axial location, a straight cylindrical BP25 bush is usually more economical; if the duty involves higher sliding speeds, higher temperatures or shock loads beyond the self-lubricating range, consider a sintered iron (FP20) or a composite friction-plate solution instead. Within this range, size the reference by matching shaft diameter to bore (22–60 mm), housing depth to length, and the frame face clearance to the collar diameter and flange thickness. With 59 variants available, select the smallest bore-length combination that carries the load to keep friction and cost low, stepping up in wall thickness (up to ~5 mm on the Ø 60 references) as shaft size and load increase.