Angular Contact Bearing Guide

Angular contact bearings have inner and outer raceways that are slightly offset, resulting in the balls mounting at an angle, making them suitable for radial and axial loads. The angular contact ball bearing advantage is that the axial load-carrying capacity increases as the contact angle increases. This article covers the design and operation of these bearings, their different types, and their applications.

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Table of contents

• What is an angular contact ball bearing?
• Types of angular contact bearings
  • Single-direction angular contact ball bearings
  • Double-row angular contact ball bearings
  • Four-point contact ball bearings
• Selection criteria
• FAQs

What is an angular contact ball bearing?

Angular contact ball bearing components

As seen in Figure 2, an angular contact ball bearing has the following components:

• Outer and inner rings (A & B): The inner ring fits over the shaft that the bearing connects to. The outer ring is the bearing's exterior. It contains and protects the bearing's components.
• Raceways (C): Angular contact bearings have inner and outer raceways. The outer raceway is asymmetrical to form the inclined contact angle.
• Balls (E): The rolling elements are spherical. They move along the raceways to reduce friction in the bearing.
• Cage (D): The cage is a separator in the raceway to keep the balls evenly spaced.

How angular contact bearings work

An angular contact bearing has an inner and outer raceway and spherical rolling elements rolling between the raceways. As seen in Figure 2, the raceways tilt towards the axial direction, so the contact angle between the balls and the raceways is inclined. This allows angular contact bearings to handle axial and radial loads at the same time.

Typical angular contact bearings are constructed to have a 15° to 25° contact angle between the raceway and rolling elements. The higher the contact angle, the higher the axial load the bearing can support.

Angular contact bearings can only support axial loads in one direction. Therefore, it's common practice to use a pair of these bearings mounted next to each other with the raceways tilting in opposite directions. An alternative is to use a double-direction angular contact valve, which is essentially two bearings joined together.

Radial load vs axial load support

Angular contact bearings are designed to handle combined radial and axial loads. Radial loads are perpendicular to the shaft and axial loads are parallel to the shaft. Read our complete rolling bearing guide to learn more about load types.

Applications

Because they can bear heavy loads, angular contact bearings are used for heavy machinery and agricultural equipment. These bearings help run pumps, electric motors, gearboxes, steel mills, windmills, conveyors, and other high-speed applications.

Types of angular contact bearings

Single-direction angular contact ball bearings

The sections above have primarily dealt with single-direction angular contact ball bearings. To summarize and add to that discussion:

• Contact angle vs load capacity: The higher the contact angle, the higher the axial load the bearing can handle. Conversely, higher contact angles lead to lower radial load capacity.
• Contact angle vs speed: While increasing the contact angle increases the axial load that the bearing can handle, it also reduces the max speed that the bearing can operate at.
• Load direction: Single-direction angular contact ball bearings can only handle axial loads in a single direction.
• Cost: Less expensive than a double-direction angular contact ball bearing.

Single-row angular contact ball bearing mounting positions

The single-row bearing must be preloaded in the direction of the contact angle, as it can only handle axial loads in that direction. Two single-row bearings can be fitted in back-to-back, face-to-face, or tandem arrangements:

• Back-to-back: Back-to-back mounted angular ball bearings (Figure 3 labeled A), the most common mountain method, can accommodate both radial and axial loads in any direction. The distance between the bearing center and the loading point (Figure 3 labeled D) is larger than other mounting methods. Therefore, the back-to-back mounting style can handle large momentary and alternating radial load forces.
• Face-to-face: Face-to-face mounted angular ball bearings (Figure 3 labeled B) can handle radial and axial loads in either direction. Due to the smaller distance between the bearing center and loading point, momentary and alternating radial force capacity is lower. Face-to-face arrangements can handle more misalignment than back-to-back arrangements.
• Tandem: A tandem mount (Figure 3 labeled C) can accommodate single-direction axial loads and radial loads. Because both bearings receive the loads on the axis, they can handle heavy axial loads.

Double-row angular contact ball bearings

The double-row angular contact ball bearing (Figure 4) is similar to two single-row bearings arranged back-to-back. In addition to radial and axial loads, they can absorb tilting moments. The advantages of double-row contact bearings include:

• Long-term cost: While typically more expensive than single-row bearings, double-row bearings can be more economical in the long run.
• Axial space: These bearings take up less axial space, which is useful when there is not enough space for two single-row bearings.
• Load accommodation: These bearings accommodate radial and axial loads, as well as tilting moments.

Four-point contact ball bearings

A 4-point contact ball bearing is similar to a single-row angular ball bearing. It consists of an outer race that is flanked on both sides. The inner race is also flanked on both sides with a split in the middle and steel balls circled by a cage. The flanks, or flanges, are symmetrical, unlike single and double angular contact bearings.

There are several advantages of four-point contact ball bearings:

• The split inner raceways of four-point contact ball bearings allow for easy mounting and dismounting of the bearing for maintenance.
• The recess in the inner raceway allows for better oil flow.
• These bearings work in a similar fashion to double-row or two single-row mounted angular contact bearings but take up less space.
• Allows for loads in both axial and radial directions.
• High load-carrying capacity due to a relatively higher number of balls than other ball bearings.

Selection criteria

Angular contact bearings are chosen when both radial and axial loads need to be supported. Consider the following when selecting angular contact bearings:

• Shaft diameter: The diameter of the shaft will determine the necessary inner diameter of the bearing.
• Bearing outer diameter: Determine if the bearing's outer diameter is suitable for the space where the bearing will be installed.
• Seal type: Should the bearing be open, shielded, or sealed?
  • Open: Open bearings have no protection against the environment, but they also have the lowest coefficient of friction. These are best for clean environments.
  • Shielded: Shielded bearings have some protection against contaminants in the environment but have lower max speed requirements than open bearings.
  • Sealed: Sealed angular contact bearings have complete protection against the environment but have the lowest max speed. Also, they are difficult to maintain, meaning a user is likely to replace a sealed bearing rather than try to repair it.
• Direction: Angular contact bearings can be single- or double-direction depending on the application's load requirements.
  • Refer to the single-row angular contact ball-bearing mounting positions section above to determine if mounting two single-direction bearings side-by-side is the best option for a given application.

FAQs

In which direction do angular contact bearings provide load capacity?

Single-row and tandem ball bearings provide one-directional thrust for axial loads. The contact angle guides the direction, which also determines the gradient of the combined load.

Do angular contact bearings need preload?

To remove excess play during bearing installation, users sustain a load pressure called preloading. Angular contact bearings require preload because they have to work in the pre-defined direction for axial loads.

 There are many different types of bearings available today with very little information on the differences between them. Maybe you’ve asked yourself “which bearing will be best for your application?” Or “how do I choose a bearing?” This bearing selection guide will help you answer those questions.

First off, you need to know that most bearings with a rolling element fall into two broad groups:

1. Ball bearings
2. Roller bearings

Within these groups, there are sub-categories of bearings that have unique features or optimized designs to enhance performance.

In this bearing selection guide, we’ll cover the four things you need to know about your application in order to choose the right type of bearing.

Find the Bearing Load & Load Capacity

Bearing loads are generally defined as the reaction force a component places on a bearing when in use.

When choosing the right bearing for your application, first you should find the bearing’s load capacity. The load capacity is the amount of load a bearing can handle and is one of the most important factors when choosing a bearing.

Bearing loads can either be axial (thrust), radial or a combination.

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An axial (or thrust) bearing load is when force is parallel to the axis of the shaft.

A radial bearing load is when force is perpendicular to the shaft. Then a combination bearing load is when parallel and perpendicular forces produce an angular force relative to the shaft.

To learn more about axial and radial ball bearings, contact our team of engineers!

How Ball Bearings Distribute Loads

Ball bearings are designed with spherical balls and can distribute loads over a medium-sized surface area. They tend to work better for small-to-medium-sized loads, spreading loads via a single point of contact.

Below is a quick reference for the type of bearing load and the best ball bearing for the job:

• Radial (perpendicular to the shaft) and light loads: Choose radial ball bearings (also known as deep groove ball bearings). Radial bearings are some of the most common types of bearings on the market.
• Axial (thrust) (parallel to the shaft) loads: Choose thrust ball bearings
• Combined, both radial and axial, loads: Choose an angular contact bearing. The balls contact the raceway at an angle which better supports combination loads.

Roller Bearings & Bearing Load

Roller bearings are designed with cylindrical rollers that can distribute loads over a larger surface area than ball bearings. They tend to work better for heavy load applications.

Below is a quick reference for the type of bearing load and the best roller bearing for the job:

• Radial (perpendicular to the shaft) loads: Choose standard cylindrical roller bearings
• Axial (thrust) (parallel to the shaft) loads: Choose cylindrical thrust bearings
• Combined, both radial and axial, loads: Choose a taper roller bearing

Bearing Runout & Rigidity

Bearing runout is the amount a shaft orbits from its geometric center as it rotates. Some applications, like cutting tool spindles, will only allow a small deviation to occur on its rotating components.

If you are engineering an application like this, then choose a high precision bearing because it will produce smaller system runouts due to the tight tolerances the bearing was manufactured to.

Bearing rigidity is the resistance to the force that causes the shaft to deviate from its axis and plays a key role in minimizing shaft runout. Bearing rigidity comes from the interaction of the rolling element with the raceway. The more the rolling element is pressed into the raceway, causing elastic deformation, the higher the rigidity.

Bearing rigidity is usually categorized by:

• Axial rigidity
• Radial rigidity

The higher the bearing rigidity, the more force needed to move the shaft when in use.

Let’s look at how this works with precision angular contact bearings. These bearings typically come with a manufactured offset between the inner and outer raceway. When the angular contact bearings are installed, the offset is removed which causes the balls to press into the raceway without any outside application force. This is called preloading and the process increases bearing rigidity even before the bearing sees any application forces.

Bearing Lubrication

Knowing your bearing lubrication needs is important for choosing the right bearings and needs to be considered early in an application design. Improper lubrication is one of the most common causes for bearing failure.

Lubrication creates a film of oil between the rolling element and the bearing raceway that helps prevent friction and overheating.

The most common type of lubrication is grease, which consists of an oil with a thickening agent. The thickening agent keeps the oil in place, so it won’t leave the bearing. As the ball (ball bearing) or roller (roller bearing) rolls over the grease, the thickening agent separates leaving just the film of oil between the rolling element and the bearing raceway. After the rolling element passes by, the oil and thickening agent join back together.

For high-speed applications, knowing the speed at which the oil and thickener can separate and rejoin is important. This is called the application or bearing n*dm value.

Before you select a grease, you need to find your applications ndm value. To do this multiply your applications RPMs by the diameter of the center of the balls in the bearing (dm). Compare your ndm value to the grease’s max speed value, located on the datasheet.

If your n*dm value is higher than the grease max speed value on the datasheet, then the grease won’t be able to provide sufficient lubrication and premature failure will occur.

Another lubrication option for high-speed applications are oil mist systems which mix oil with compressed air and then inject it into the bearing raceway at metered intervals. This option is more costly than grease lubrication because it requires an external mixing and metering system and filtered compressed air. However, oil mist systems allow bearings to operate at higher speeds while generating a lower amount of heat than greased bearings.

For lower speed applications an oil bath is common. An oil bath is when a portion of the bearing is submerged in oil. For bearings that will operate in extreme environments, a dry lubricant can be used instead of a petroleum-based lubricant, but the lifespan of the bearing is typically shortened due to the nature of the lubricant’s film breaking down over time.

There are a couple of other factors that need to be considered when selecting a lubricant for your application, see our in-depth article “How to Choose the Correct Ball Bearing Lubricant".

Are you interested in learning more about Angular Contact Ball Bearing? Contact us today to secure an expert consultation!