Cylindrical Bronze Bushings BP25 — 02 to 15

BP25 sintered bronze is deliberately manufactured with roughly 20–25% interconnected porosity, and those voids are impregnated under vacuum with a low-viscosity mineral bearing oil. At rest the oil is held in the pores by surface tension. When the shaft turns, the combination of frictional heat — which lowers the oil's viscosity and makes it expand — and the hydrodynamic pressure generated in the converging gap draws a thin film of oil out of the pores onto the sliding surface, so the shaft effectively rides on a self-replenishing oil film rather than on dry metal.

When motion stops and the bearing cools, capillary action reabsorbs the oil back into the porous bronze, ready for the next start. This continuous exchange keeps the running coefficient of friction low — typically around 0.05–0.10 for this material class — and lets the bearing operate maintenance-free for the design life of most light-duty mechanisms, provided the impregnated oil is not washed out by solvents or driven off by excessive heat.

These cylindrical bushings are retained by an interference fit in the housing, so no adhesive or additional locking is normally required. Handle them clean and dry — never wipe the bore with solvent, which strips the impregnated oil.

• Bore the housing to an H7 tolerance and add a 0.5–1 mm lead-in chamfer so the bushing starts squarely.
• Press the bushing home with a smooth, polished arbor that bears on the full end face; avoid hammer blows, which distort the thin wall and burnish over the surface pores.
• Remember that the bronze wall contracts on pressing, so the finished running bore closes by a small amount — size it after fitting with a ball or plug. Never ream or machine the bore, as cutting smears metal across the pores and destroys the self-lubricating action.
• Use a ground shaft in the h6–f7 range with a surface finish of Ra ≤ 0.4 µm for the best oil-film performance.
• Keep solvents, hot degreasers and cutting fluids away from the bushing; if it is accidentally washed dry, re-impregnate it in warm bearing oil before use.

Choose this BP25 cylindrical range when you need a compact, self-lubricating plain bearing for shafts between Ø2 and Ø15 mm and the housing can react the radial load through a simple straight bore. If the assembly must also take an axial thrust or locate against a shoulder, select the equivalent flanged BP25 bushing instead. Where duty is heavier — slow speeds under high load, frequent starts, or shock — the higher-strength FP20 sintered iron or SO16 alloy grades carry more load than sintered bronze; for larger shafts, step up to Bushingo's wider-bore cylindrical series. BP25 remains the default first choice wherever low friction, quiet running, corrosion resistance and maintenance-free operation matter more than peak load capacity.