ASTM C90300 Tin Bronze Bushings and Bearings

C90300 is commonly known as SAE 620 bearing bronze or tin bronze. It is widely specified for bushings, bearings, and wear components because it offers a practical balance of strength, machinability, corrosion resistance, and anti-friction performance. When reviewing equivalents, buyers should still confirm chemistry, mechanical properties, and application requirements against the governing drawing or material specification.

C90300 is a cast tin bronze alloy used for bushings, bearings, and general wear parts. It is valued for good load-carrying capability, reliable machinability, and resistance to wear in properly designed bearing applications. The alloy is often selected for industrial equipment where dimensional stability, smooth running surfaces, and dependable service life are important to the finished assembly.

Many bronze bushings do require lubrication, especially in higher-load, higher-speed, or oscillating applications. Proper grease or oil helps reduce friction, limit heat buildup, and extend service life. However, lubrication needs depend on shaft finish, operating environment, load, speed, and whether the design uses grooves or oil-impregnated alternatives. Application-specific review is important before finalizing the part.

The best bronze for bushings depends on load, speed, lubrication method, shaft material, and environmental exposure. C90300 tin bronze is a strong general-purpose choice for many bearing applications because it machines well and provides dependable wear performance. For heavier loads, shock conditions, or specialized lubrication demands, other bronze alloys may be more suitable based on the operating requirements.

C90300 bronze can be machined into plain bushings, flanged bushings, liner sleeves, drill bushings, and custom-profile bearing components. M.A.R.'s Engineering supports both thin-wall and heavy-wall configurations, along with close-tolerance bore and OD requirements. Secondary finishing and grinding can also be applied where the application calls for tighter fit, smoother surfaces, or improved assembly consistency.

Tolerance capability depends on part geometry, wall thickness, diameter, and finishing requirements, but M.A.R.'s Engineering offers centerless grinding with tolerances up to 0.0001 inches and surface finishes as fine as 4 μin. For bronze bushings and bearings, this supports accurate outside diameters, improved concentricity, and smoother running surfaces that help the finished component perform consistently in service.

Yes. M.A.R.'s Engineering supports prototype quantities as well as high-volume production runs. The company combines CNC turning, Swiss machining, single-spindle and multi-spindle screw machining, grinding, and in-house finishing to scale production efficiently. That allows customers to move from early validation to repeat manufacturing with fewer vendor transitions and better continuity in quality and process control.

M.A.R.'s Engineering operates with ISO compliant quality processes and cites full traceability across production. The company also lists compliance with Mil-1-45208A and applies in-process quality controls across machining and finishing operations. For buyers sourcing bronze bushings and bearings, that means stronger documentation, more consistent dimensional verification, and better confidence in repeatability from lot to lot.