Why use Bronze Bearings ?
Updated: Sep 5
Bronze is a versatile and popular bearing material to work with for various applications. Its wide selection of alloys and compositions provides a host of properties. Bronze Bearings demonstrate strength, durability and corrosion resistance.
Both bronze and brass are copper-based alloys containing various other elements. They belong to materials referred to as “red metals” because of their reddish color. Bronze Bushings (Copper - Tin ) are harder and stronger compared with Brass Bushings (Copper-Zinc), which are softer and thus more likely to deform or break.
Range of Properties
Bronze Bearings offer exceptional mechanical properties in various demanding operating and environmental conditions:
Strength
Low friction
Shock and impact resistance
High load capacity
Wide temperature range
Cost-effective solution
And since bronze is recyclable, it is considered as a sustainable material.
Bronze Bearing Applications
Bronze Bushings and Bearings are commonly used in high-load, low-speed and heavy-duty applications and equipment and can be found in a wide range of industries:
Aerospace (flight control system, landing gear assemblies, aircraft components)
Automotive (sway bars, control arms, vehicle suspension components)
Energy (gearbox assemblies and yaw mechanisms in wind turbines, turbine shafts in hydroelectric power plants)
Food processing
Industrial (pivot points, rotating shafts)
Bronze Bearing Types
Bronze Bushings can be produced in many shapes and dimensions:
Cylindrical Bearings (also called Sleeve Bearings): used to reduce friction and vibration under heavy loads and high temperatures
Flanged Bearings (and Double Flanged Bearings): typically used for light duty
Thrust Bearings (also called Thrust Washers): offering easy assembly, a high load capacity and resistance to harsh environments
Bearing Plates: Where low coefficient of sliding friction is desired
Pintle Bearings
Bronze Bearing Materials
Bronze Bearings are available in different copper alloys:
They are listed in five alloy families according to their compositions and properties:
Leaded Tin Bronze for antifriction and machinability properties
High Leaded Tin Bronze alloys for lubrication and machinability properties
Aluminum Bronze alloys for strength and corrosion resistance properties
Manganese Bronze alloys for strength and corrosion resistance properties
Nicomet® Spinodal Bronze for superior high-strength and anti-galling properties
Grease grooves are typically wider and deeper than oil grooves. This is to hold a supply of grease and to provide for the thick grease to be forced in. Oil grooves typically vary in width but are shallower than grease grooves. Most oil grooves are operating in a constant loss or closed oiling system that continually feeds the less viscous oil to the grooves. Double loop groove & double figure eight groove recommended for grease only.
Groove selection can be influenced by many things such as operating environment, type of lubricant, supplemental lubrication feed system, load etc.. The following information is intended as a guide. Consideration must be given to all factors.
Double loop - Double figure 8 Mixed film lubrication. Load is partially supported by lubrication. Speeds from 10 to 25 s.f.m. will induce this condition. Most cast bronze bearing applications are in this category.
Straight Groove - Good for long bearings. It should be located in the unloaded area of the bearing. Circular - is used when the direction of load varies and a pressure fed lubricant system is present.
Straight Circular groove - is applied in cases where the direction of the load varies and the lubricant is not pressure fed.
Boundary lubrication is where none of the load is supported by the lubricant. Bearings which are only periodically lubricated will at some time operate under these conditions. Speeds which are 10 s.f.m. or less will cause boundary lubrication.
In full film lubrication the load is separated from the bearing by a film of lubricant. A minimum speed of 25 s.f.m. will generally be needed. The same types of grooving used in mixed film will work in the full film application.
Installation and Maintenance of Bronze Bearings
Assembly and maintenance of Bronze Bushes are critical to performance and durability.
The selection of the appropriate lubricant is crucial and depends on the operating conditions (load, speed and temperature).
A typical running clearance for a bronze bearing is around 0.001 inches per inch of shaft diameter; meaning, for a 1-inch shaft, you would aim for a clearance of approximately 0.001 inches between the shaft and the bearing bore, with variations depending on the specific application, load, speed, and type of bronze alloy used.
For example is the normal bearing clearance is .001” per inch of shaft diameter +.001”, i.e. 5” shaft = .006” (5.006”). Alternately, the clearance should be .00125”/inch of shaft diameter.
Shaft size: Larger shafts generally require slightly larger clearances.
Operating conditions: High-speed or high-load applications might need slightly smaller clearances for better stability.
Lubrication: Adequate lubrication allows for slightly larger clearances.
Type of bronze used: Different bronze compositions may have different wear characteristics, impacting clearance requirements.
Graphite lubrication on the ID face of the bearing will enable you to obtain long bearing life both at high operating temperatures, and in applications lacking a supplemental lubrication. The graphite acts as a dry lubricant and provides maintenance-free continuous lubrication. The ID groove patterns can be filled with a special hardenable graphite paste. Graphite Plugs can be press fit through the wall of the bearing with a special epoxy resin binder. Typical plug diameter is 7mm with a 25% surface coverage. The graphite plugs can be placed around special features of your parts.
Graphite bronze parts should be run dry with no oil or grease. When EP2 grease mixes with the shed particles of the dry graphite plugs, it creates a sticky, abrasive slurry. This slurry traps dust and airborne grit, grinding away the precision clearances of the bearing instead of protecting it. The oil matrix in grease prevents the graphite from properly transferring to the mating shaft. This stops the formation of the intended low-friction dry film.
Correct Maintenance Practices for Graphite Plug Bearings:
Run them completely dry: In most standard applications, graphite plug bearings require zero external lubrication.
Keep them clean: Periodically wipe the mating shafts with a clean cloth or isopropyl alcohol (IPA) to remove grit and stray poly-dust. Do not apply wet lubricants.
Our graphite plug bearings typically have a coefficient of friction between 0.10 and 0.15, depending on a variety of factors affecting performance.
