Types

A roller bearing is a cylindrical unit that is used to provide low-friction movement for a bushing or bearing block. A ball bearing is a spherical unit that accomplishes the same objective as a roller bearing. Roller bearings on the other hand, have an entire line of contact.

Types

• Deep-Groove Ball Bearings. The most commonly used bearings are Deep-Groove Ball Bearings.
• Angular Contact Ball Bearings.
• Self-Aligning Ball Bearings.
• Thrust Ball Bearings.
• Spherical Roller Bearings.
• Cylindrical Roller Bearings.
• Tapered Roller Bearings.
• Needle Roller Bearings.

rolling friction

Ball bearings are the most common type of bearings and are found in many every day objects, such skateboards, blenders, bicycles, DVD players and photocopiers. This type of bearing is typically used in applications which have a high speed and a low load.

There are many different types of bearings, each used for specific purposes and designed to carry specific types of loads, radial or thrust. Here, we’ll look at the 6 most popular types: plain bearings, rolling element bearings, jewel bearings, fluid bearings, magnetic bearings, and flexure bearings.

The first digit indicates the width or height series (dimensions B, T or H). The second digit identifies the diameter series (dimension D). The last two digits of the basic designation identify the size code of the bearing bore. The size code multiplied by 5 gives the bore diameter (d) in mm.

A bearing number is composed of a basic number and a supplementary code, denoting bearing specifications including bearing type, boundary dimensions, running accuracy, and internal clearance.

low friction seal

Bearing internal clearance is defined as the total distance either inner or outer ring can be moved when the other ring is fixed. If movement is in the radial direction, it is called radial internal clearance; if in the axial direction, axial internal clearance.

Following are some of the most prominent methods used onboard ships to measure the clearance of main bearing:

1. 1) Bridge with Depth Gauge.
2. 2) Bridge With Feeler Gauge.
3. 3) Telescopic or Swedish Feeler Gauge.
4. 4) Dial type Depth Gauge.

Ideally, there should be zero residual radial play in the bearing to minimize ball skidding and reduce axial play (end play) so correct selection of the initial radial play is important.

A slight press fit will generally help prevent creep, but an excessive press fit will eliminate the bearing internal clearance and cause a rise in operating temperature that can lead to early failure.

For instance, internal radial clearance of a deep-groove ball bearing mounted on a solid steel shaft with an interference fit of 0.013 mm (0.0005 in.) may be reduced as much as 0.010 mm (0.0004 in.) by the mounting.

A clearance fit, or slip fit, always enable clearance between the bearing bore and shaft, or outer ring and housing. In this fit, often referred to as a press-fit, there is interference between the bearing ring and its mating part.

Both ISO and ANSI have standardised fits in three classes – clearance, transition and interference.

When a ball bearing is used, it is not used only by itself. It is always fitted to either a shaft or a housing bore. Fit is the value of tightness between the shaft and bearing bore when the bearing is installed. Fit can also be the tightness between the housing bore and the bearing outside diameter.

For example, in H7/h6 (a commonly-used fit) H7 represents the tolerance range of the hole and h6 represents the tolerance range of the shaft. The potential range of clearance or interference can be found by subtracting the smallest shaft diameter from the largest hole, and largest shaft from the smallest hole.

C3 – Refers to a “greater than standard clearance”. This is the most common type of bearing, and is the correct choice for the majority of applications. C4 – Refers to “greater than C3 clearance”.

While ovens, hot plates and oil baths work, the simplest method to heat a bearing is with an induction heater. The process is quick, accurate, repeatable and safe. Make sure operating instructions and warnings are followed because induction heaters create a strong magnetic field which can be a hazard.