Angular Contact Ball Bearings

What is an angular contact ball bearing?

An angular contact ball bearing is a rolling bearing whose inner and outer ring raceways are offset from each other along the axis of the bearing. Because of this offset, the balls touch the rings at an angle rather than straight across, creating a line of contact that is tilted relative to the bearing’s centre line. This tilt is called the contact angle, and it allows the bearing to carry combined loads, meaning radial loads and axial loads acting at the same time.

In a standard deep groove ball bearing, the balls contact the rings almost straight across, so the bearing is best at carrying radial loads. In an angular contact ball bearing, the angled contact means that axial forces are transmitted efficiently through the balls, giving much higher axial load capacity. The larger the contact angle, the more axial load the bearing can carry.

A single-row angular contact ball bearing is made up of four main parts:

• Inner ring - fits on the shaft, with a raceway that has one high shoulder and one lower shoulder
• Outer ring - fits in the housing, with an offset raceway that also has one high shoulder and one lower shoulder
• Balls - a single row of balls that carry the load at the contact angle
• Cage - keeps the balls evenly spaced and guides them, made from polyamide, pressed steel, machined brass, or phenolic resin

Key features:

• Combined loads - carries radial and axial loads together
• One-direction axial load - a single-row bearing supports axial load in one direction only, so it is usually mounted against a second bearing
• Contact angle - commonly 15, 25, 30, or 40 degrees, with larger angles giving higher axial load capacity and smaller angles favouring higher speeds
• High speed capability - well suited to high speeds, especially in precision designs
• High rigidity - when mounted in pairs with preload, they give a very stiff, accurate shaft support
• Single row, double row and paired designs - available in different configurations for different load and space requirements
• Wide size range - from small precision bearings to large bearings for heavy machinery

In simple terms, an angular contact ball bearing is a bearing designed to hold a shaft accurately in place while supporting forces from the side and along the shaft at the same time. 

Why are angular contact ball bearings essential?

Angular contact ball bearings are essential wherever a rotating shaft must carry both radial and axial loads, often at high speed and with high accuracy. Many machines produce combined loads, such as helical gears pushing sideways and along the shaft, pump impellers creating thrust, or cutting forces acting on a machine tool spindle. A deep groove ball bearing can only take limited axial load, and a thrust bearing cannot take radial load, so angular contact ball bearings provide an efficient solution that handles both. 

Their main benefits are:

• Combined load capacity - they support radial and axial loads together in a single bearing position
• High axial load capacity - the contact angle allows them to carry much greater thrust than deep groove ball bearings
• High speed performance - low friction and precise geometry make them ideal for fast-running shafts
• High rigidity and accuracy - mounted in preloaded pairs or sets, they eliminate internal play and give a very stiff, precise shaft support
• Flexible arrangements - they can be combined in pairs or sets; they eliminate internal play and give a very stiff, precise shaft support
• Accurate axial positioning - they keep the shaft located precisely along its length, which is important for gears, spindles, and rotors
• Compact solution - they can replace a combination of separate radial and thrust bearings
• Wide choice - many contact angles, cage materials, precision classes, and configurations are available

These qualities make angular contact ball bearings important in a wide range of applications, including:

• Machine tools - spindles for lathes, milling machines, grinding machines, and machining centres, where accuracy and rigidity are critical
• Pumps and compressors - centrifugal pumps, screw compressors, and turbo machinery, where impellers and rotors create thrust
• Gearboxes - shafts carrying helical, bevel, and worm gears
• Electric motors - high-speed motors and spindle motors
• Automotive - wheel hubs, differentials, transmissions, and steering systems, often using double row designs
• Ball screw supports - special high contact angle bearings that support ball screws in machine tools and automation
• Fans and blowers - high-speed industrial fans
• Aerospace and defence - high-speed, high-precision rotating equipment
• Robotics and automation - precision joints and drives
• Medical and dental equipment - high-speed handpieces and precision instruments

The main types of angular contact ball bearings

Angular contact ball bearings are usually grouped by the number of ball rows, contact angle, mounting arrangement, precision class, and cage design

By design:

• Single row angular contact ball bearings - the most common type, carrying axial load in one direction. They are usually mounted against a second bearing to locate the shaft in both directions
• Double row angular contact ball bearings - similar to two single row bearings mounted back to back, but combined in one unit. They carry radial loads and axial loads in both directions in less width than a pair of single row bearings
• Four-point contact ball bearings - a special single row design with gothic arch raceways that carries axial loads in both directions
• Ball screw support bearings - angular contact designs with a high contact angle, often around 60 degrees, giving very high axial stiffness for ball screw drives
• Super-precision angular contact ball bearings - made to very tight tolerances for machine tool spindles and other high-speed, high-accuracy applications

By contact angle:

• 15 degrees - used mainly in precision bearings for very high speeds and lower axial loads
• 25 degrees - a balance of speed and axial load capacity, common in precision and general bearings
• 30 degrees - common in general bearings and double row designs
• 40 degrees - the standard for many general industrial single-row bearings, giving high axial load capacity

By mounting arrangement:

• Back-to-back arrangement - the load lines spread outwards, giving a stiff arrangement that resists tilting moments. It carries axial loads in both directions
• Face-to-face arrangement - the load lines point inwards, giving a less stiff arrangement that is more tolerant of misalignment. It also carries axial loads in both directions
• Tandem arrangement - both bearings face the same way and share a heavy axial load in one direction. It is usually combined with another bearing to take thrust in the other direction
• Universally matchable bearings - made so they can be mounted in any of these arrangements without needing a factory-matched set, with a defined clearance or preload

By cage design:

• Polyamide cages - lightweight, quiet and low friction, suitable for many applications within their temperature limits
• Pressed steel cages - strong and suitable for general industrial use
• Machined brass cages - robust and suited to high speeds, high temperatures, vibration, and tough conditions
• Phenolic resin and high-performance polymer cages - common in super-precision bearings for very high speeds

Other options:

• Sealed or shielded bearings  - particularly in double row designs, keeping out contamination and holding lubricant for life
• Hybrid bearings - fitted with ceramic balls for higher speeds, lower heat generation, and longer life in demanding applications
• Stainless steel bearings - for wet, food processing, marine, or corrosive environments 

How to choose the right angular contact ball bearing?

Choosing the right angular contact ball bearing means matching it carefully to the loads, speed, accuracy, and mounting arrangement. Because these bearings are often used in pairs or sets, the arrangement and preload are just as important as the bearing itself. Work through these points in order:

• Dimensions - match the bore to the shaft diameter and check the outside diameter and width against the housing and available space
• Load direction and size - consider both radial and axial loads, and whether axial loads act in one or both directions. Check the static and dynamic load ratings in the catalogue
• Contact angle - choose a larger contact angle, such as 40 degrees, for higher axial loads, or a smaller contact angle, such as 15 or 25 degrees, for higher speeds and lighter axial loads
• Single or double row - choose single row bearings for flexibility and adjustable arrangements, or double row bearings for a compact unit that takes axial loads in both directions
• Mounting arrangement - use back-to-back for high stiffness and resistance to tilting, face-to-face for better tolerance to misalignment, and tandem for heavy one-direction thrust
• Preload or clearance - decide whether the application needs axial clearance, zero clearance, or preload. Preload increases rigidity and accuracy but also increases friction and heat, so it must be chosen carefully
• Speed - check speed ratings for the chosen size, contact angle, cage, and lubrication. For very high speeds, consider precision bearings, smaller contact angles, or hybrid bearings with ceramic balls
• Cage material - choose polyamide for general quiet running, pressed steel for general use, brass for tough conditions, or phenolic and high-performance polymers for very high speeds
• Lubrication - choose grease for simplicity and moderate speeds, or oil, oil-air, or oil mist lubrication for very high speeds and heat removal
• Environment - use sealed, stainless steel, or specially coated bearings for contamination, moisture, or corrosive conditions
• Mounting accuracy - make sure shaft and housing seats are accurate and that bearings in sets are mounted in the correct orientation, as incorrect mounting will change the load lines and can cause early failure

FAQ - All you need to know about angular contact ball bearings

Can a single row angular contact ball bearing be used on its own?

Usually not. Because it carries axial load in one direction only and produces an internal axial force under radial load, it is normally mounted against a second bearing.

What does universally matchable mean?

It means the bearings are made so that any two can be mounted together in any arrangement and still give the specified clearance or preload, without needing a factory-matched set.

Do they need lubrication?

Yes. Grease is common for moderate speeds, while oil, oil-air, or oil mist lubrication is used for very high speeds and better cooling. Sealed double-row bearings are usually greased for life.

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What causes them to fail?

Common causes include incorrect mounting orientation, too much or too little preload, poor lubrication, contamination, overloading, misalignment, and excessive heat at high speeds.

How do I know when to replace one?

Signs include noise, vibration, overheating, loss of accuracy, excessive play, rough rotation, or visible wear, pitting, or discolouration on the rings and balls.