What is a Spherical Bearing?

When a shaft doesn't sit in perfect alignment with its housing — because of manufacturing tolerances, thermal expansion, or deflection under load — something has to absorb that angular error, or the bearing fails early. That's the job of a spherical bearing.

Spherical bearings are one entry in a long list of industrial bearings and bearing types, but they're the ones purpose-built for exactly this problem.

Unlike most rolling-element bearings, which are built for pure rotation, spherical bearings are built around misalignment. This guide covers the two main types — spherical plain bearings and spherical roller bearings — how each is constructed, where they differ, and how to choose between them.

What Is a Spherical Bearing?

A spherical bearing is any bearing whose contact surface is machined as a section of a sphere, which lets the inner and outer rings rotate relative to each other in more than one plane. That extra degree of freedom is what keeps the bearing working even when the shaft and housing aren't perfectly aligned.

Two distinct bearing families use this spherical geometry, and it's worth being precise about the difference — the terms get used interchangeably online, which causes confusion:

• Spherical plain bearings — the inner and outer ring surfaces slide directly against each other. No rolling elements.

• Spherical roller bearings — two rows of barrel-shaped rollers sit between the rings and roll rather than slide.

Both accommodate misalignment. They differ in how much misalignment they tolerate, how fast they can run, and how they're maintained — which is what the rest of this guide covers, type by type.

Spherical Plain Bearings

Design and Components

A spherical plain bearing has just two moving parts:

• Inner ring — mounts on the shaft; its outer diameter is machined to a convex spherical surface.

• Outer ring — sits in the housing; its bore is machined to a matching concave spherical surface.

There's no cage and no rolling elements like those in ball bearings or roller bearings — the two spherical surfaces bear directly against each other.

• Steel-on-steel — needs regular grease, but tolerates the highest static and shock loads.

• PTFE composite liner — bonded to the spherical surface; runs dry and maintenance-free, at lower load and speed limits.

• Sintered bronze — a middle ground, with partial self-lubrication and moderate load capacity.

This single-surface design is also why spherical plain bearings tolerate more misalignment than spherical roller bearings — some radial spherical plain bearing series allow up to 10–15°, depending on size and design, compared with roughly 1.5–3° for spherical roller bearings.

Full cross-section. The inner and outer ring share one spherical surface — there are no rolling elements between them.

Configurations

Beyond liner material, spherical plain bearings are built in four load-direction configurations:

• Radial — carries radial load mostly through the shaft. The most common configuration.

• Angular contact — the sliding surface sits at an angle to the bearing axis, carrying combined radial and axial load in one direction.

• Thrust — oriented for axial load, used where load runs mostly along the shaft.

• Rod ends — a spherical plain bearing pressed into a housing with an integrated shank (male or female thread) to connect a rod to a pivot point.

Applications

Because they tolerate high misalignment and static or shock loads, spherical plain bearings show up wherever a joint pivots slowly, or where perfect alignment can't be guaranteed:

• Vehicle suspension and steering linkages — must move with the suspension geometry through its full travel.

• Hydraulic and pneumatic cylinder rod ends — acting as the pivot connecting the piston rod to the load.

• Construction and agricultural equipment articulating joints — excavator buckets, loader arms.

• Aircraft control linkages — which commonly use rod ends built to specifications such as AS81820 or the NAS series. See our aerospace spherical bearing guide for details.

When selecting a spherical plain bearing, the load rating, required range of motion, operating environment, and expected service life should all be checked against the specific series — not assumed from a general catalog spec.

Spherical Roller Bearings

Design and Components

A spherical roller bearing is built very differently from its plain-bearing counterpart. Instead of one sliding interface, it has:

• Outer ring — one ring with a single, common concave spherical raceway shared by both rows of rollers.

• Inner ring — one ring machined with two raceways, each inclined at an angle to the bearing axis.

• Rollers — two rows of barrel-shaped rollers riding in those raceways.

• Cage — pressed steel, machined brass, or polymer, spacing the rollers and keeping each row aligned.

Because the outer ring's raceway is spherical rather than cylindrical, the inner ring and both rows of rollers can pivot together inside the outer ring — that's the self-aligning mechanism. It's a fundamentally different route to the same result as a spherical plain bearing: tolerance to misalignment through geometry, rather than through a single sliding surface.

Top-half cross-section shown; the bottom half mirrors it. One continuous outer raceway serves both rows — only the inner ring is split.

Configurations

Spherical roller bearings are specified along three independent variables:

• Row count — nearly all are double-row; single-row spherical roller bearings exist but are far less common.

• Bore type — cylindrical bore, pressed directly onto a precision-ground shaft, or tapered bore, mounted with an adapter sleeve when the shaft can't be machined to a tight tolerance.

• Sealing — open bearings rely on internal clearance to let grease circulate and run cooler at higher speed; sealed versions add seals that keep lubricant in and contaminants out, trading some speed for longer relubrication intervals.

Most industrial catalogs — SKF's 222, 223, 230, 231, 232, and 239 series, for example — organize their spherical roller bearing range this way, by bore type and row width, before getting into sealing options.

What Is a Spherical Roller Bearing Used For?

Spherical roller bearings earn their keep in equipment that combines heavy load, continuous rotation, and a working environment where perfect shaft alignment isn't realistic:

• Gearboxes and vibrating screens — in mining and aggregate processing.

• Paper machine rolls — and other long-shaft applications prone to deflection.

• Wind turbine main shafts and gearboxes.

• Vertical pumps and agitators — where the bearing carries radial load plus its own axial weight.

Spherical Plain Bearings vs. Spherical Roller Bearings

How to Choose Between the Two

Four questions narrow the decision fast:

• Misalignment — more than a couple of degrees, common in suspension and linkage applications, usually rules out a spherical roller bearing.

• Motion type — plain bearings suit slow oscillation and pivoting; roller bearings suit sustained rotation at speed.

• Load direction — radial load with occasional shock favors a plain bearing; combined radial-and-axial load under continuous rotation favors a roller bearing.

• Maintenance access — a sealed roller bearing or a PTFE-lined plain bearing both cut relubrication frequency, useful once equipment is hard to reach.

When in doubt, match the bearing to how the joint actually moves, not just the load it carries — that mismatch is the most common selection mistake we see.

Conclusion

Spherical plain bearings and spherical roller bearings solve the same core problem — misalignment — through opposite mechanisms: one slides, one rolls. Match that mechanism to how your joint moves and how much maintenance access you have, and the load ratings mostly take care of themselves.

Need help matching a bearing to your application? LILY Bearing's engineering team can review your load, speed, and misalignment requirements and recommend — or manufacture — the right spherical bearing for the job.