What is a Ball Bearing? | How does Ball Bearing Work?

The bearings are most commonly used in different applications. They are used in machines to transfer motion from one moving part to another and to reduce friction between the moving parts. The ball bearing is a most commonly used type of bearings. The ball bearings are used in rotary applications to provide smooth, low-friction motion. Ball bearings offer high performance and long life in transferring loads from the ball to the inner ring. This article explains the different aspects of the ball bearing.

What is a Ball Bearing?

The ball bearing is a type of bearing that contains a ball to maintain the clearance between the bearing races. The motion of the ball reduces the friction compared to flat surfaces sliding against each other.

Ball bearing

The main function of the ball bearing is to support axial and radial loads and decrease rotational friction. It uses at least two races to support the ball and transfer the load through the ball.

Most commonly, one race is connected to a rotating component (such as a shaft or hub) while the other race is fixed. When the race rotates, the ball also rotates. Due to the ball rotation, the coefficient of friction is less than the two flat surfaces rubbing against each other.

These bearings have a small contact area between the races and the ball. Therefore, the load-carrying capacity of ball bearings tends to be lower than that of other types of bearings.

One of the disadvantages of ball bearings is that the ball “flattens” over time and can eventually fail if the outer race is subjected to excessive pressure. Therefore, you must regularly check the rated load and other parameters.

Construction of Ball Bearing

The ball bearing has the following major parts:

  1. Two races (or rings)
  2. Ball spacer (retainer)
  3. Rolling elements (ball)

Angular contact ball bearings and radial ball bearings contain inner and outer rings. Angular contact ball bearings and radial ball bearings are most commonly used to carry radial loads. The outer race is fixed.

Ball Bearing Construction

The outer race helps to shift radial loads from the bearings to the casing. The inner ring connects to the turning shaft. This inner race assists and directs the shaft while rotating.

The rolling element helps to support the loads and deliver them along the raceway. The rolling element rotates around the inner races.

The ball bearing contains a separator that works as a fence between the balls and stops the balls from colliding with each other. Thrust ball bearings are installed to carry the axial load (i.e., a load parallel to the axis of rotation). They contain two races of the same size.

Types of Ball Bearings

Ball bearings have the following major types:

  1. Radial Bearing
  2. Deep Groove Bearing
  3. Angular Contact Bearing
  4. Self-aligning Ball Bearing
  5. Thrust Ball Bearing

1) Radial Ball Bearings

These types of ball bearings are used to support both axial (thrust) and radial loads. However, radial ball bearings are only used to support pure axial loads.

2) Deep Groove Bearing

The deep groove bearing is also known as a radial bearing. These bearings have the ability to take varying degrees of axial and radial loads. They are employed when the primary load is in the radial direction.

The deep groove bearing has balls, a cage, an outer race, and an inner race. The cage is used to separate the balls.

3) Angular Contact Bearing

An angular contact ball bearing creates a contact angle between the ball and the races during the operation of the bearing.

They are best suitable to support the axial loads. This load (or preload) makes a line of contact between the outer race, the ball, and the inner race. This preload may be produced inside the bearing or produce when the bearing is installed into the assembly.

4) Self-aligning Ball Bearings

The self-aligning ball bearing has two sets of balls. These balls have the ability to align themselves. They have the ability to support both light axial and radial loads.

5) Thrust Ball Bearings

These types of ball bearings are used to support pure thrust loads. They can’t carry the radial load. The rotating element can be a roller, a needle, or a ball. Slewing races have the ability to support radial, axial, and moment loads.

The races are not attached to the body or shaft but are attached directly to the seating surface. There are mounting bores on the outer and inner races. The outer race, inner race, or both may contain integral gear. 

Ball Bearing Types Base on Construction

1) Conrad

In the Conrad ball bearing, the inner race installs in an eccentric position relative to the outer race. The inner and outer races make contact at one point to create a large gap on the opposite side of the contact point. The resulting gap is used to insert the ball.

A cage is utilized to maintain the position of the balls relative to each other. Without the cage, the ball will ultimately become misaligned during bearing working, and the bearing will ultimately fail. The cage just maintains the position of the balls, but it can’t support loads.  

2) Slot-fill Bearing

These ball bearings have notches on one side of the outer and inner rings that allow the ball to slide into the resulting groove and assemble the bearing.

One of the main advantages of the slot-fill bearings is that more balls can be installed (allow a perfect match design to be possible), which increases the radial load-carrying ability of the bearing. Therefore, these bearings have more radial load-carrying ability than Conrad bearings of the same size and material type.

3) Fractured race

The fractured race is the most famous method to add more balls to radial ball bearings, place the ball in, reassemble the damaged section, and then use a pair of steel strips to align the damaged sections of the bearing.

4) Row Ball Bearing

The row ball bearings have two types:

  1. Single-row bearing
  2. Double row bearing

The single-row bearing contains a single row of balls. It is ideal for both thrust and radial loads.  

The double-row bearing contains two rows of the ball. Each row contains an equal number of balls. The main advantage of double-row bearing is that it has the ability to support both axial and radial loads in both directions. These bearings have a steep mounting.

5) Flanged Bearing

The flange on the outer race of the bearing simplifies axial positioning. The casing of this type of bearing contains a uniform diameter through-hole, but the entry surface (outer or inner surface) of the housing is machined perpendicular to the axis of the hole. However, these flanges have high production costs.

6) Caged

Cages usually are installed to hold balls in the Conrad-style ball bearing. According to the cage design, the number of balls and the load carry capacity can be reduced. In the absence of a cage, the sliding of the two convex surfaces relative to each other stabilizes the tangential position.

Specifications of Ball Bearing

  1. Bore: Bearings with metric diameter bores used in different industries contain a standard numbering system. For bore size 04 or above, multiply by 5 to get the bore in millimeters. If your ball bearing contains a hexagonal hole, refer to the dimensions across the flats. If the hole is conical, it represents the smallest diameter.
  2. Outside diameter: The bearing’s outer diameter contains the housing (for housed units) but not the flange (for flanged bearings). The width of the outer race is the total width of the outer of the bearing.
  3. Overall Width: The locking collar is known as the overall width of the bearing.

Applications of Ball Bearing

  1. The ball bearings are used in computer fans and household electrical fans.
  2. In the watch industry, Jean Lassalle developed a watch movement that uses a ball bearing to decrease the motion thickness. The Caliber 1200 uses 0.20mm balls and is only 1.2mm thick, but it’s still the thinnest mechanical movement.
  3. Ball bearings are used in many industrial applications such as jet engine shafts, gearboxes, and pulleys.
  4. The skateboard wheels use two bearings that have the ability to support both radial and axial time-varying loads.
  5. They are used in fidget spinners.
  6. They commonly use in reciprocating pumps and centrifugal pumps.

FAQ Section

What is the function of the Ball Bearing?

A ball bearing is the most famous type of bearing. The ball bearing has the following function:

  1. Supports the load
  2. Decreases the friction
  3. Position the rotating parts of the machine

What are the types of ball bearings?

  1. Radial bearing
  2. Thrust ball bearing
  3. Deep groove bearing
  4. Self-aligning ball bearing
  5. Angular contact bearing

What are the parts of the ball bearing?

  1. Outer race
  2. Inner race
  3. Ball spacer (retainer)
  4. Rolling elements (ball)
  5. Separator
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