Thrust Bearing: A Big Little Part

Well-designed parts stand the test of time. Take the thrust bearing, for example. Developed in the early 1900s, it’s a little part that’s deceptively simple. It changed the automotive and transportation industries by making better, more powerful propellers and engines possible. Today, there is more than one type of thrust bearing. Most of them wind up in vehicles. You’ll find some in other types of applications such as centrifuges and generators. Let’s take a look at what a thrust bearing is and the different types available.

A Special Part With a Specific Job

In general, a bearing allows parts that sit close together to rotate freely. A thrust bearing is a special type of bearing that is designed to assist rotation around a fixed shaft or axis. Naturally, not all axial loads are the same. Consequently, different types of thrust handle different loads.

Thrust Bearing Types

Ball Thrust Bearing

This thrust bearing is the basic model: bearing balls inside a ring sitting between two grooved washers. The grooves allow the balls to move. This type of thrust bearing is useful with small axial loads.

Roller Thrust Bearings

The roller thrust bearing design is similar to ball thrust bearings—a set of bearings inside a ring fitted between two washers. However, the bearings are rollers instead of balls. This type of thrust bearing can support bigger loads thanks to the cone or cylindrical shape of the rollers. The roller bearings provide a larger contact area that enables them to hold up under greater thrust load. Roller thrust bearings have three sub-types:

• cylindrical—cylinder-shaped rollers positioned to point to the bearing’s center or axis. They’re the most inexpensive type of roller thrust bearing. However, they wear out faster than ball thrust bearings because the friction and circular speed are higher.
• tapered—tapered rollers also arranged pointing to the bearing’s axis. The tapering requires precise calculations to figure the diameter of both ends and the length of the roller so they’ll roll easily without slipping or catching. They cost more to make but using them in pairs supports axial thrust in opposite directions. Two tapered roller thrust bearings working together also assists with radial load.
• spherical—rollers are circular but asymmetrical. On top of supporting high combined axial and radial loads, spherical roller thrust bearings also enable performance when axes are misaligned. This type of roller thrust bearing has the highest load rating. That means it’s useful in heavy-duty machines such as cranes and drills.

Because different roller thrust bearings support different levels of axial load, some shops stock them all. Of course, if most of your customers need one particular type, you might be able to negotiate a better price on high-quality thrust bearings and stock more of them.

Thrust Bearings for Other Purposes

Two more types round out the thrust bearing collection, but you typically won’t find them in trucks or cars. Fluid thrust bearings have a thin film of pressurized fluid in place of ball or roller bearings. That means low friction and drag. Uses include generators and water turbines.

Then there’s the magnetic thrust bearing. It, too, has low drag because a magnetic field replaces the physical bearings. The magnetic design also allows for very high speeds. Magnetic thrust bearings are used in a variety of ways, such as in electric meters, equipment inside vacuums, and even in heart pumps.

Though modified over time, the basic thrust bearing design remains the same. It’s a seemingly simple little piece that plays a big part in the heavy-duty industry and beyond.