Thrust bearings are a distinct category of rolling element bearings designed specifically to support axial (thrust) loads — forces that act parallel to the shaft axis rather than perpendicular to it. Understanding the different types of thrust bearings is essential for any engineer or procurement professional specifying bearings for pumps, gearboxes, marine propulsion systems, crane slewing rings, or machine tool spindles. This guide defines each thrust bearing type, explains the load directions each handles, and maps them to real industrial applications.
What Is a Thrust Bearing?
A thrust bearing is a rolling element bearing whose primary function is to resist loads acting along the axis of rotation. In contrast to radial bearings, which carry loads perpendicular to the shaft, thrust bearings are built to prevent axial displacement of rotating components. Some thrust bearing designs handle purely axial loads; others handle combined axial and radial loads depending on their geometry.
Thrust bearings are classified into two broad groups: ball thrust bearings and roller thrust bearings. Within each group, there are single-direction and double-direction variants depending on whether axial force acts in one direction or alternates between two.
Thrust Ball Bearings: Single and Double Direction
Single-direction thrust ball bearings carry axial loads in one direction only. They consist of two washers (shaft washer and housing washer) and a ball complement retained in a cage. These bearings cannot carry radial loads and must always be used in combination with a radial bearing when combined loading is expected. They are widely used in low-to-medium speed applications such as vertical pump shafts, steering columns, and machine tool rotary tables.
Double-direction thrust ball bearings carry axial loads in both directions — the shaft washer sits between two housing washers. This design suits applications where axial forces reverse periodically, such as screw compressors, hydraulic pumps, and machine tool spindles. Speed capability for thrust ball bearings is limited; at high RPM, centrifugal forces on the balls cause cage wear, making angular contact ball bearings the preferred substitute at higher speeds.
Cylindrical Roller Thrust Bearings
Cylindrical roller thrust bearings replace balls with cylindrical rollers arranged radially around the shaft axis. The line contact of rollers (versus point contact of balls) gives these bearings a significantly higher axial load capacity at lower speeds. They are compact in the axial direction and commonly specified in heavy gearboxes, crane hooks, and large hydraulic cylinders.
The limitation of cylindrical roller thrust bearings is that they produce sliding friction at the roller-washer contact zone — especially at the roller ends — which generates heat at higher speeds. They are therefore limited to slow-speed, heavy-load applications. The KG International product catalogue covers cylindrical roller bearings for both radial and thrust applications across cement, steel, and marine industries.
Tapered Roller Thrust Bearings
Tapered roller thrust bearings use tapered rollers inclined at an angle to the shaft axis, enabling them to handle combined axial and radial loads simultaneously. The geometry allows for precise rolling contact across the raceway without sliding, improving efficiency and load distribution. They are available in single-row and double-row configurations.
These bearings are extensively used in heavy vehicle axle drives, industrial gearboxes, and large turbine applications. Their ability to carry both thrust and radial loads makes them highly versatile — eliminating the need for separate bearing arrangements.
Spherical Roller Thrust Bearings
Spherical roller thrust bearings are among the most capable bearings available for heavy combined loading. They use barrel-shaped rollers between a shaft washer and a housing washer, with the housing raceway ground to a spherical profile. This design provides:
• Very high axial load capacity
• Significant radial load capability (up to approximately 55% of axial load)
• Self-aligning capability — compensates for shaft misalignment and deflection
• Suitability for moderate to high speeds relative to other roller thrust types
These bearings are specified for vertical shaft applications such as large vertical pumps, hydro turbines, marine propulsion shafts, and heavy press machines. In cement and mining industries, spherical roller thrust bearings appear in vertical roller mill gearboxes, where combined loads and shaft misalignment co-exist.
For lubrication, spherical roller thrust bearings require grease with the correct base oil viscosity for the operating speed and temperature. KG Ultra Grease (GP3, HT2, AB3 variants) provides the viscosity and thermal stability required for these demanding applications.
Angular Contact Ball Bearings as Thrust Bearings
While not classified as thrust bearings in the strictest sense, angular contact ball bearings carry significant axial loads and are frequently used where thrust ball bearings would be limited by speed. Their contact angle (15°, 25°, or 40°) determines the proportion of axial to radial load capacity. At a 40° contact angle, angular contact ball bearings approach the load-carrying capability of a single-direction thrust ball bearing at substantially higher permissible speeds.
They are the preferred bearing type for pump impeller shafts, spindle bearings, and high-speed gearbox applications where thrust loads are significant.
Thrust Bearing Selection Reference
| Bearing Type | Axial Load | Radial Load | Self-Aligning | Typical Speed | Application Examples |
|---|---|---|---|---|---|
| Thrust Ball (single) | Medium | None | No | Low–Medium | Pumps, rotary tables |
| Thrust Ball (double) | Medium | None | No | Low–Medium | Compressors, spindles |
| Cylindrical Roller Thrust | High | None | No | Low | Gearboxes, crane hooks |
| Tapered Roller Thrust | Very High | Moderate | No | Low–Medium | Axles, turbines, gearboxes |
| Spherical Roller Thrust | Very High | Moderate–High | Yes | Medium | Vertical pumps, hydro turbines |
Conclusion
The choice of thrust bearing type depends entirely on the load magnitude, load direction, speed, and whether misalignment is present in the shaft system. For heavy combined loads with misalignment — as found in cement mills, vertical pumps, and marine applications — spherical roller thrust bearings are the clear engineering choice. For simpler, lighter axial loads at moderate speeds, thrust ball or cylindrical roller thrust bearings are cost-effective solutions.
KG International supplies a full range of thrust bearings and associated housings from its Jebel Ali distribution hub, serving 50+ countries across 5 continents.
All brand names and standards referenced in this article are the property of their respective organisations. KG International is not the manufacturer of OEM brand bearings.