Solid Bearing Blanks BP25

BP25 sintered bronze contains roughly 20-25% interconnected porosity that behaves like a sponge holding lubricating oil throughout the body of the material. At rest, capillary action retains the oil within the pore network. When a shaft turns against a machined surface, frictional heat and the local pressure of the moving journal cause the oil to expand and migrate out to the sliding interface, where it forms a thin hydrodynamic film that separates shaft and bearing.

As the assembly cools or the motion stops, capillary force draws the oil back into the pores, so the reservoir is continually recirculated rather than consumed. This is why an oil-impregnated bronze bearing runs maintenance-free and needs no external greasing for much of its service life - provided the machined running surface keeps its open porosity and is not smeared closed by dull tooling. The performance you obtain therefore depends directly on how the blank is finished, not only on the material itself.

These are semi-finished blanks: the running surface is created by your own machining, so tool condition governs the finished bearing's performance. Handle them as oil-charged parts and protect the impregnation throughout the process.

• Use sharp, polished carbide tooling with positive rake, light cuts and moderate feed; blunt tools smear and close the surface pores, destroying the self-lubricating action.
• Machine dry or rely on the impregnated oil to lubricate the cut - avoid flooding with water-based coolant, which can flush lubricant from the pores. If coolant is unavoidable, or after heavy stock removal, re-impregnate the part by soaking it in warm oil.
• Leave a finishing allowance and bring the final bore to size with a fine finishing cut or by roller-sizing/burnishing after press-fit to reach the required tolerance and surface finish.
• Press the finished bush into a rigid H7 housing with an appropriate interference; the bore closes slightly on fitting, so size the bore after mounting wherever running clearance is critical.
• Chamfer the lead-ins, run against a ground shaft, and avoid steam-cleaning, aggressive degreasing or high-temperature baking of the finished part, all of which drive off the impregnation oil.

Reach for Solid Bearing Blanks BP25 when a standard bored sintered bush cannot give you the bore, outside diameter, length or flange you need, or when the tolerances and profile are special enough to justify machining from solid. If your dimension already matches a stock cylindrical or flanged bush, a ready-bored part is faster and more economical. Where high loads, edge loading or oscillating dry conditions dominate, consider the sintered iron FP20 grade for greater strength, or a Metagliss composite plate for flat sliding surfaces. Choose BP25 bronze blanks when you want the balance of good conformability, corrosion resistance and quiet, maintenance-free running that tin-bronze provides, together with the freedom to cut your own geometry from a single homogeneous piece.