A thrust washer is a flat, washer-shaped plain bearing that carries axial load — the force acting along the axis of a shaft, often called end load or thrust. Unlike a sleeve or flanged bushing, it does not wrap around the shaft to carry radial load; its job is to sit between two faces and let them slide past each other while resisting the force pushing them apart. In cast bronze, a thrust washer is a compact, low-profile way to control axial load in industrial equipment. This page covers the geometry, how the load is carried, the cast bronze base material, materials, standards, self-lubricating variants, and selection.
What a Thrust Washer Does
A thrust washer provides a sliding face that resists axial force and locates a shaft or component in the axial direction. It is used where the dominant load is end-wise rather than radial — for example, to take up end-float, to position a gear or collar, or to carry the axial reaction of a screw, cam, or pivot. Because the part is a thin disc, it fits into spaces where a full thrust bearing would not.
d, the outer diameter D, and the thickness s. The load is supported over the annular contact area between d and D — roughly π/4 × (D² − d²) — so the same axial force spreads over a larger face as D increases relative to d.
Cast Bronze: The Base Material
Most thrust washers in this catalog are machined from cast bronze — a continuous-cast tube or bar, or a sand-cast disc, finished to the required inner diameter, outer diameter, and thickness. Cast bronze gives a dense, uniform structure that machines cleanly and carries load well, and it is well suited to the grooves and plug holes used in self-lubricating variants. The alloy is chosen for the duty: aluminum and nickel-aluminum bronzes for strength and corrosion resistance, manganese bronze for heavy pivots, phosphor or silicon bronze for fatigue resistance and stability, and tin/leaded tin bronzes where machinability and anti-friction behavior matter. Cast bronze differs from sintered (powder-metallurgy) strip, which is a porous preform rather than a solid machined part.
Where Cast Bronze Thrust Washers Are Used
A cast bronze thrust washer is chosen where the load is end-wise (axial) and a thin disc fits the space — not where radial support is the main need:
- Screw jacks, lead screws, and jack shafts — controlling end-float and taking the axial reaction of a translating shaft.
- Gearbox and transmission end locations — locating gears, collars, or spacers axially without a full thrust bearing.
- Hydraulic and pneumatic cylinder rod ends — absorbing the axial force at a pivoting or extending joint.
- Swivel joints, turntables, and slewing interfaces — rotational parts that also carry a steady axial face load.
- Pivots with an axial reaction — paired with a separate radial bearing that handles the side load.
Fitness and exercise equipment is covered in the gym equipment bearings guide. For a specific application example, see Thrust Washers for Tractor Plant.
Dimensions and Standards
Ring-type thrust washers made from strip are dimensioned by ISO 6525:2018 (Plain bearings — Ring type thrust washers made from strip — Dimensions and tolerances). Cast or machined washers follow the same copper-alloy dimensioning practice as ISO 4379:2024 and DIN 1850; GB/T 2889 covers plain-bearing vocabulary. A flat washer’s fit is set by the bore clearance on the shaft or spigot and by the flatness of the two sealing faces, not by a shaft/bore running fit. For self-lubricating washers, the groove or plug layout is placed on the sliding face, clear of the heavily loaded track.
Specs & Selection
| Part | Load carried | Form | When to use |
|---|---|---|---|
| Thrust washer | Axial only | Flat disc | Pure end load in a thin space; usually paired with a radial bearing |
| Flange bushing | Radial + axial (one part) | Cylinder with an integral shoulder | Radial support and axial location needed together in one bushing |
| Thrust bearing (retained) | Axial, often with a cage | Washer pair with rolling or grooved elements | Higher axial load or speed needing a contained assembly |
A thrust washer is the simplest axial option. Where radial load also exists, a flange bushing combines both in a single part; where axial demand is high or guided, a retained thrust bearing may be chosen instead. See the flange bushings page for the combined radial-and-axial case.
| Alloy family | Examples | Role in cast bronze thrust washers |
|---|---|---|
| Aluminum bronze (low-lead) | C95400, C95500 | High strength and wear resistance for heavy, slow axial loads and corrosive service. |
| Nickel aluminum bronze (low-lead) | C63000 | Seawater-resisting corrosion behavior for submerged or coastal use. |
| Manganese bronze (low-lead) | C86300 | High mechanical strength for heavy pivots and oscillating axial load. |
| Phosphor bronze | C51000, C52100 | Fatigue resistance and dimensional stability under repeated axial load. |
| Silicon bronze | C65100, C65500 | Good general corrosion resistance for marine and outdoor structures. |
| Tin and leaded tin bronzes | C93200, C93700, C93800, C94300 | Good machinability and anti-friction behavior; leaded grades are not described as lead-free. |
| Lubrication style | How it works | Recommended for | Note |
|---|---|---|---|
| Graphite-plugged face | Solid graphite plugs in holes or grooves on the sliding face lay down a dry film under motion | Heavy, slow, or no-oil-trace duty | Primary self-lubricating build in this catalog |
| Oil grooves | Spiral, radial, or figure-eight grooves hold and spread lubricant for periodic or assisted lubrication | Applications with a planned lubrication path | Keeps a liquid film in a confined face |
| PTFE / polymer-faced | Dry-running liner bonded to a bronze backing | Oil-trace-free duty at moderate load | Secondary option; considered where a polymer face is acceptable |
For the material build, see the graphite bronze bushings page and the oilless bushings overview.
- Confirm the load is mainly axial; if radial load also exists, consider a flange bushing or a paired radial bearing.
- Set the face geometry — inner diameter
d, outer diameterD, thicknesss— from the available space and the annular contact area needed. - Choose a cast bronze alloy by environment (corrosion exposure) and by whether leaded grades are acceptable.
- Decide lubrication: graphite-plugged cast bronze or oil grooves for the standard build; a PTFE-faced variant where an oil-trace-free face is required and load is moderate.
- Validate against the actual axial load, sliding speed, and environment rather than a generic rating.
Frequently Asked Questions
What is the difference between a thrust washer and a flange bushing?
A thrust washer carries axial load only as a flat disc; a flange bushing carries radial load through the bore and axial load through its integral shoulder in one part. Use a washer for pure end load in a thin space, and a flange bushing where radial and axial support are needed together.
Can a thrust washer replace a thrust bearing?
For low-speed, heavy, or intermittent axial load in a confined space, a cast bronze thrust washer is often the simpler choice. For higher axial load or speed needing a contained assembly, a retained thrust bearing may be more suitable. The decision depends on the actual duty, not a generic rule.
How is a thrust washer’s load capacity estimated?
The axial load is supported over the annular contact area between the inner diameter d and the outer diameter D — approximately π/4 × (D² − d²). A larger face (higher D relative to d) spreads the same axial force over more area and lowers the surface pressure. Actual capacity still depends on alloy, surface speed, and duty, and should be confirmed against the supplier specification.
Do thrust washers need lubrication?
Plain cast bronze washers benefit from a lubrication path; graphite-plugged variants are made to run with little or no external oil, and oil-grooved washers use periodic lubrication. Service need still depends on load, speed, and contamination, and should be confirmed from the supplier specification.
