Needle Roller Thrust Washers
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Needle Roller Thrust Washers
What is a needle roller thrust washer?
A needle roller thrust washer is a flat, hardened steel ring that gives the needles of a thrust cage a raceway to run on. Needle roller thrust cages can run directly on a hardened shaft shoulder or housing face, but when those surfaces are not hard enough or smooth enough, thrust washers are fitted instead. The washer takes the wear, protecting the shaft and housing, and can be replaced on its own.
A standard thrust washer has three main features:
- A flat raceway face, which the needles roll on
- A bore, which fits over the shaft
- An outer diameter, which fits the housing recess.
Washers are usually fitted on one or both sides of the cage.
- A washer next to the shaft shoulder acts as the shaft washer and rotates with the shaft.
- A washer next to the housing face acts as the housing washer and stays still.
Thrust washers are made from hardened chrome steel or hardened spring steel, with the raceway face finished flat and smooth. Thin washers are hardened right through so they stay flat under load, while thicker washers are precision ground on both faces.
Why are needle roller thrust washers essential?
They let needle roller thrust cages be used on shafts and housings that cannot be hardened and ground, which saves the cost and time of heat-treating and grinding those parts. If the raceway wears, only the washer needs replacing rather than the shaft or housing, which makes servicing quicker and cheaper.
They are low in cost, easy to fit, and come in standard sizes that match the thrust cages. Their dimensions are standardised, so a washer of a given reference has the same bore, outer diameter, and thickness, regardless of which reputable manufacturer makes it.
Typical applications include:
- Automotive gearboxes and transmissions
- Differentials and transfer cases
- Planetary gear sets
- Steering systems
- Pumps and compressors
- Power tools
- Agricultural and construction machinery
- Swivel joints and turntables
- Household appliances
The main types of needle roller thrust washers
- Thin thrust washers (AS) - These are thin, hardened washers, around 1mm thick in many sizes. They can be used as either the shaft or housing washer, but need a flat, rigid surface behind them, as they are too thin to support the load on their own.
- Thick thrust washers (LS) - These are thicker, precision-ground washers. They can be used as either the shaft or housing washer, and suit designs where the surface behind them is less rigid or less accurate.
- Washers supplied with a cage - A thrust cage supplied with one or two washers as a complete, ready-to-fit thrust bearing.
- Metric and inch washers - Both are widely available. Metric washers are sized in mm, while inch washers are sized in fractions of an inch and usually come in more than one thickness.
How to choose the right needle roller thrust washer?
- Size and dimensions - The bore must suit the shaft and the outer diameter must fit the housing recess. The washer must match the size of the thrust cage it runs with.
- Thickness - Choose a thin washer where space is tight and there is a flat, rigid surface behind it. Choose a thicker washer where the support is less rigid, or where a thin washer might bend under load.
- Support surface - Whichever washer is used, the face behind it must be flat and square to the shaft. An uneven support will bend the washer and overload parts of the raceway.
- One or two washers - Fit a washer on each side where neither the shaft shoulder nor the housing face is hardened. Fit only one if one of the faces is already hardened and ground.
- Load - Check the washer suits the axial load and any shocks. Use the load ratings for the complete thrust bearing, which are published in manufacturers’ catalogues.
Essential references and specialised ranges
How the numbering works:
The letters at the start identify the type:
AS = thin thrust washer
LS = thicker thrust washer
The numbers show the bore and outer diameter in mm:
The first two digits are the bore, and the last two are the outer diameter, so an AS 1226 has a 12mm bore and 26mm outer diameter.
Washers share the same numbers as the matching thrust cage, so AS 1226 and LS 1226 washers are used with an AXK 1226 cage.
For bores of 100mm and above, the number is longer, such as AS 100135.
Always check the bore, outer diameter, and thickness before ordering a replacement.
Suffixes:
Thrust washers rarely carry suffixes. Where they do, they usually show a special tolerance, material, or surface treatment.
Suffix codes vary between manufacturers, so check the supplier’s catalogue for the exact meaning.
FAQ - All you need to know about needle roller thrust washers
When do I need a thrust washer?
You need a thrust washer if the shaft shoulder or housing face is not hardened and ground to a smooth, flat finish. If both faces are already hardened and ground, the thrust cage can run directly on them and no washers are needed.
What is the difference between AS and LS washers?
AS washers are thin and need a flat, rigid surface behind them to support the load. LS washers are thicker and precision ground, so they can be used where the support behind them is less rigid or less accurate.
Can a washer be used as either the shaft or housing washer?
Yes. Standard AS and LS washers can be used on either side of the cage. A washer against the shaft shoulder acts as the shaft washer, and one against the housing face acts as the housing washer.
Which way round does a thrust washer go?
The smooth, finished raceway face should face the needles. On thin washers, both faces are often the same, but on some washers one face is finished as the raceway, so check before fitting.
Click here to learn how to maintain a bearing.
Can I replace a thrust washer myself?
In most cases, yes. The washer simply slides onto the shaft and sits against the shoulder or housing face. Check the surface behind it is clean, flat, and free from burrs, as any unevenness will bend the washer. Always replace a washer if it shows wear tracks, and consider replacing the thrust cage at the same time.
How do I identify a thrust washer I need to replace?
The reference is not usually marked on the washer, so it is best identified by its dimensions. Measure the bore, outer diameter, and thickness with callipers. It also helps to check the reference of the thrust cage it runs with, as the washer will usually share the same numbers.
Click here to learn how to measure a bearing.
How can I tell if a thrust washer is worn or damaged?
Warning signs include:
- A ring-shaped wear track on the raceway face
- Pitting, flaking, or grooves where the needles run
- Dents in the raceway at regular intervals, matching the needle spacing
- Blue, brown, or straw-coloured marks from overheating
- A washer that is bent, cracked, or no longer flat
- Rust or corrosion on the raceway face
