Bearings are indispensable parts for many industries. They are used in factories, construction sites, households, the automotive sector and more. They are also used in light-duty equipment.
This article describes the different types of bearings and their working mechanism.
What is the function of bearings?
Bearings are responsible for taking on the load of rotation to prevent the shaft from breaking. There are two types of load to keep in mind when we discuss bearings - radial load and thrust load. Radial loads are perpendicular to the axis of the shaft. Thrust load acts at an angle to the parallel.
Types of bearings
Bearings can be broadly classified into two types: rolling bearings and plain bearings.
Rolling bearings use rolling elements such as balls and rollers, between the outer and inner rings. They operate by the friction created using rolling.
Compared to plain bearings, rolling bearings are characterized by superior maintainability and other features. Grease is generally used to lubricate rolling bearings. Since grease is accompanied by adhesion to the friction surfaces and sealing properties, it is considered more convenient for lubrication and sealing devices compared to oil lubrication.
Plain bearings are the simplest form of bearings.They have no rolling elements.
As the shaft rotates, a wedge-shaped gap is created between the shaft and the bearing. In a plain bearing, lubricant enters the gap, generating an oil film pressure called fluid lubrication. Through this mechanism, a plain bearing has a structure that supports the rotation of the shaft and the load.
The main categories and features of plain bearings are as follows
Resin type bearings
- Structure: Single-layer (resin-based)
- Main applications: Automobile parts, construction machinery, OA equipment
- Structure: Double-layer (resin + sintered bronze + back metal alloy + back metal, etc.)
- Main applications: bicycles, construction machinery, OA equipment
- Structure: Single-layer (metallic)
- Main applications: General industrial machinery, hydraulic equipment
Spherical plain bearings
- Structure: Oilless/lubricated
- Main applications: Robots, link mechanisms of transport equipment, machine tools, etc
Characteristics of Rolling and Plain Bearings
Rolling bearings and plain bearings have different characteristics. Here is a comparison of their characteristics.
Generally speaking, rolling bearings are inferior to plain bearings in terms of impact load. From this point of view, plain bearings are suitable for heavy loads and impact loads.
Rolling bearings have no problem when used at low speeds, but plain bearings are not suitable for use only at very low speeds.
Impact Resistance, Water Resistance, and Acoustics
Plain bearings are considered superior in terms of impact resistance. Sliding bearings are also superior in terms of water resistance, although this depends on the type of bearing. Also, the acoustics of plain bearings are relatively low, whereas rolling bearings are louder.
Rolling bearings are subject to cracking, chipping, and seizure due to rolling fatigue. On the other hand, plain bearings are considered to have an unlimited life due to fluid mechanics.
Rolling bearings are generally lubricated with grease, which simplifies maintenance. Even when oil lubrication is used, maintenance is relatively easy. On the other hand, plain bearings, which mainly use oil lubrication, are more complicated to maintain than rolling bearings because of the need to prevent oil leaks and other problems.
When selecting bearings, the first consideration is generally rolling bearings, which are easy to use and maintain. If the use of rolling bearings is difficult, the use of plain bearings is often considered. Plain bearings are characterized by their high load carrying capacity and quiet operation.
A note on Rolling Bearings vs Ball Bearings
Another common type of bearing is ball bearing. The main difference between rolling bearing and ball bearing is in the unit used to produce movement and the contact surface. In the case of roller bearing, a cylindrical unit is used and the contact surface is large. In the case of ball bearing, a spherical unit or ball is used and there is a small contact area.
Ball bearings are often less expensive, and are easily replaceable and are widely used across many industries. However they may be a little noisy.
There are several different types of bearings based on the amount of force they can support and their working mechanism. Please note that there are many more types of bearings apart from the ones covered here.
MonotaRO has a wide selection of all types of bearings. You can choose from different bearings depending on the application.