What Is the Difference Between Radial Load and Axial Load?

Radial load vs axial load comes down to direction. A radial load acts perpendicular to the shaft axis and pushes the shaft sideways against the bearing. An axial load, also called a thrust load, acts parallel to the shaft axis and pushes or pulls the shaft along its length. The difference between radial load and axial load decides which bearing designs can carry the force without overloading their rolling elements and raceways.

This article explains each load type, where each one comes from in industrial machinery, which bearings suit each case, and what engineers should check when both act together.

What Is a Radial Load in a Bearing?

A radial load is a force that acts at right angles to the shaft axis. In a horizontal shaft, it acts vertically or sideways. The bearing transfers this force from the shaft through the rolling elements to the raceways, and then into the housing. Only the rolling elements on the loaded side of the bearing carry the force at any moment, which is why radial load capacity depends heavily on bearing geometry and size.

Common Sources of Radial Load

Radial load in bearings arises from several machine elements:

• Belt and chain tension: The pull of a belt or chain on a pulley or sprocket bends the shaft and loads the supporting bearings sideways.
• Gear forces: Meshing gears produce tangential and radial force components, and both act perpendicular to the shaft axis.
• Rotor and shaft weight: The mass of a motor rotor, fan impeller or roll presses down on the bearings.
• Unbalance and transverse forces: Rotating unbalance creates a radial force that rotates with the shaft.

Electric motors, conveyor pulleys, fans and gearbox shafts all carry radial load as their primary duty.

Which Bearings Suit Radial Loads?

Deep-groove ball bearings, cylindrical roller bearings and needle roller bearings are the usual choices for radial loads. Cylindrical and needle roller bearings have line contact between rollers and raceways, which gives them higher radial capacity than a ball bearing of similar size. Needle roller bearings suit applications where radial space is tight.

Where a shaft carries mainly radial force at moderate to high speed, a Radial Load Bearing such as a deep-groove ball bearing is a common starting point, and the available single row and double row designs let engineers match the bearing to the duty. Radial load capacity still varies with size, internal geometry, material and manufacturer specification, so no single type is right for every radial application.

What Is an Axial Load in a Bearing?

An axial load is a force that acts parallel to the shaft axis. It tries to slide the shaft lengthways through its supports. Bearings that carry axial load must keep the shaft in its correct position along its axis and resist movement in one or both directions.

Common Sources of Axial Load

Axial load in bearings comes from machine-specific forces:

• Helical gears: The angled teeth produce an axial force component along with the radial and tangential components.
• Screw mechanisms and worm drives: The thread or worm engagement pushes the shaft along its axis.
• Pump thrust: Pressure differences across an impeller create axial thrust on the shaft.
• Bevel gears and clutches: Both generate axial components under load.
• Thermal expansion: A shaft that grows with temperature pushes against any bearing that restrains it axially.

Which Bearings Suit Axial Loads?

Thrust ball bearings and thrust roller bearings are built mainly for axial loads. Thrust ball bearings support axial load in one direction (single direction) or both (double direction), and they do not suit significant radial load. Thrust roller bearings, including cylindrical, tapered and spherical roller designs, carry heavier axial loads than thrust ball bearings of comparable size, and each design has its own limits on speed, misalignment and any accompanying radial load.

When axial force dominates and the bearing position carries little radial load, an Axial load bearing such as a thrust ball bearing gives engineers a bearing designed for that direction of force. Angular contact ball bearings and tapered roller bearings also support axial load, but they do so together with radial load, as the combined loading section explains below.

Many radial bearings cannot safely carry large axial loads. A cylindrical roller bearing with no ribs on one ring, for example, allows the shaft to move axially and carries no axial load at all.

What Is the Difference Between Radial Load and Axial Load?

The table summarises radial load vs axial load across the points engineers check first.

Load direction and load magnitude are separate questions. A bearing can have an adequate rating for the size of a force and still be wrong for its direction.

Which Bearings Handle Radial Loads, Axial Loads, and Combined Loads?

Bearing suitability depends on the specific design and operating conditions. The summary below describes general behaviour, and manufacturer data confirms the limits for any individual bearing.

• Deep-groove ball bearings: They carry radial load and a moderate axial load in both directions. The axial capacity is limited, so heavy or continuous thrust needs a different design.
• Cylindrical roller bearings: They carry high radial loads. Designs with ribs on both rings can also locate the shaft axially and carry a limited axial load, while designs without such ribs allow axial movement and carry none.
• Needle roller bearings: They carry radial load in a compact cross-section and do not support axial load in their basic form.
• Thrust ball bearings: They carry axial load only, in one or both directions depending on the design.
• Thrust roller bearings: They carry heavier axial loads, and some designs tolerate a degree of shaft misalignment or a small radial component.
• Angular contact ball bearings: Their contact angle lets them carry combined loads, and a single bearing supports axial load in one direction only. Paired arrangements carry axial load both ways.
• Tapered roller bearings: They carry combined radial and axial loads, with axial capacity increasing with the contact angle. A single bearing carries axial load in one direction only, so engineers mount them in opposed pairs.

Can a Bearing Handle Both Radial and Axial Loads?

Yes, within its limits. Angular contact ball bearings, tapered roller bearings, and some deep-groove and cylindrical roller designs carry both load types. The ratio of axial to radial load matters as much as the sizes of the forces, because it changes how the load distributes across the rolling elements.

How Do Radial and Axial Loads Affect Bearing Selection?

A common bearing selection mistake is to consider load magnitude without first checking its direction. Direction comes first, then magnitude, then the operating conditions around them.

Load ratings. The basic dynamic load rating relates to fatigue life under rotation. It corresponds to a load that a group of identical bearings would carry for one million revolutions with 90 per cent surviving. The basic static load rating applies to a stationary or very slowly rotating bearing and relates to permanent deformation at the contact points. The two ratings answer different questions, and engineers use each in its place. A rating is also not a permitted maximum load under every condition.

Radial load and bearing life. Fatigue life falls steeply as load rises. Ball bearing life varies with the cube of the ratio of dynamic rating to equivalent load, and roller bearing life follows a power of 10/3. A modest increase in radial load therefore shortens life by a larger proportion.

Combined loading. When a shaft experiences both radial and axial forces, engineers must evaluate the combined loading condition rather than treating each force in isolation. Manufacturers publish calculation methods that convert the two forces into one equivalent dynamic load, using factors that depend on the bearing’s geometry and the ratio of axial to radial load. Contact angle, internal clearance and bearing arrangement all affect the result.

Speed and lubrication. Higher speed raises operating temperature and limits the load a bearing carries reliably. Lubricant type and supply must suit both speed and load. Thrust bearings often face sliding at the contact surfaces, so lubrication needs close attention in axial applications.

Alignment and mounting. Shaft misalignment concentrates load on part of the raceway. Incorrect fits, housing errors and wrong preload or clearance settings shift the real load away from the calculated one.

Shock loads and operating conditions. Impact, vibration, contamination and temperature variation all reduce margins that a steady-load calculation assumes.

Manufacturer specifications. Load ratings, limiting speeds and axial load limits come from the manufacturer’s data for the exact bearing. Engineers should use that data rather than a general rule for the bearing type.

Common Bearing Load Selection Mistakes to Avoid

These errors recur in industrial bearing selection:

1. Selecting by dimensions alone. Matching bore, outside diameter and width identifies a bearing that fits, not one that suits the load.
2. Confusing radial load capacity with axial load capacity. High radial capacity does not indicate high axial capacity. Check each rating separately.
3. Ignoring axial forces from gears and other components. Helical gears, worm drives and pumps generate thrust that a radial-only calculation leaves out.
4. Assuming every radial bearing carries significant axial load. Some designs carry none, and others carry only a limited amount.
5. Ignoring combined loads. Treating radial and axial forces separately underestimates the real load on the bearing.
6. Overlooking speed, alignment, lubrication and operating conditions. These factors set the working margin around the nominal rating.
7. Using load ratings without evaluating the application. A rating describes a standard test condition, and the application rarely matches it exactly.

Incorrect load assumptions can contribute to excessive wear, overheating, noise, vibration and shorter bearing life. The cause of an early failure is rarely a single factor, so engineers should review load, arrangement and conditions together.

Conclusion

Radial load acts perpendicular to the shaft axis, and axial load acts parallel to it. Radial bearings such as deep-groove, cylindrical roller and needle roller types carry radial load. Thrust bearings carry axial load. Angular contact and tapered roller bearings carry both in combination, within the limits of their design and arrangement.

Understanding the direction of forces comes first. Engineers then evaluate combined loading, compare the applied load against the correct dynamic and static ratings, and check speed, lubrication, alignment, mounting and shock conditions. The right bearing depends on the application, not on load direction alone.

If you are reviewing bearing options for a specific shaft arrangement, S. Goel Bearing & Co. can help you identify suitable bearing types. You can explore the product range on the website or contact the team with your application details for a product enquiry.