Cylindrical Bronze Bushings BP25 — 35 to 125

Oil-impregnated sintered bronze acts as a self-contained hydrodynamic bearing. During sintering the bronze powder is consolidated but deliberately left with roughly 20–25% interconnected porosity by volume — a fine capillary network that is then vacuum-filled with lubricating oil. At rest, the oil is held inside the wall by surface tension. When the shaft begins to turn, frictional heat and the pressure wedge under the rotating journal draw oil out of the pores to the bearing surface, where it forms a load-carrying film that separates the metal faces.

As the assembly slows and cools, that oil is reabsorbed into the porous structure by capillary action, ready for the next cycle. This continuous internal exchange delivers long, lubricant-free service without external oiling or greasing. Sliding speed is the main driver of film formation, so the mechanism is most effective on steady rotary duties; very slow or heavily shock-loaded motion benefits from the thicker wall sections available at the upper end of this range.

Sintered bronze bushings are installed by press-fit and must not be reamed after mounting, because cutting tools smear the surface and close the oil-bearing pores that make the bearing work.

• Machine the housing bore to a clean H7 tolerance and add a small lead-in chamfer so the bush starts square.
• Press with a piloted, polished mandrel that bears on the full end face; never hammer directly on the sintered material.
• Allow for bore close-in: the interference fit reduces the inner diameter slightly after pressing. Where a precise running clearance is critical, finish the bore with a ball-sizing or burnishing tool rather than a reamer or boring bar.
• Keep the shaft journal smooth — a ground finish is ideal — to preserve the oil film and minimise wear.
• Handle clean and dry; avoid solvents, degreasers or hot washing that would leach the impregnated oil out of the wall.
• On the longer sizes in this range (lengths up to 120 mm), press progressively and check alignment so the bush is not cocked in a deep bore.

Choose this BP25 range when you need cylindrical (unflanged) bearings for medium-to-large shafts in the Ø35–125 mm band and want the higher sliding-speed capability, quiet running and corrosion resistance of sintered bronze. Bronze suits continuous rotary duty at moderate loads; if the bearing must also carry axial thrust or locate a component endwise, select a flanged BP25 bush instead. Where cost is the priority and speeds are low with higher static loads, a sintered iron (FP20) equivalent may be preferable, while SO16 alloy or Metagliss composite plates address higher-temperature or flat-sliding requirements. Within the 66 variants, match the bore to your shaft first, then confirm the housing can accept the corresponding outside diameter and length.