Bearings can be classified in various ways and based on the core logic of "friction mode" and "force direction" in actual engineering application scenarios the three most basic and widely used types can be summarized which are rolling bearings plain bearings and thrust bearings with details as follows:
I. Rolling Bearings
1. Definition and Core Characteristics
Rolling bearings are a type of bearing that relies on the rolling motion of internal rolling elements (such as balls and rollers) to realize shaft rotation and their core function is to convert sliding friction between the shaft and the bearing into rolling friction. They can be further divided into "radial rolling bearings" (carrying radial loads) and "angular contact rolling bearings" (carrying both radial and axial loads) according to the force direction and they are currently the most widely used bearing type in the industrial field.
2. Structure and Materials
The core components of rolling bearings include the inner ring (tightly fitting the shaft) the outer ring (fitting the bearing housing) rolling elements (mostly made of high-carbon chromium bearing steel GCr15 and in forms such as balls cylindrical rollers tapered rollers) a cage (mostly made of stamped steel or engineering plastic to separate rolling elements and prevent collisions) and some sealed models include a seal/dust cover. The rolling elements and the inner and outer ring raceways of rolling bearings need to be machined with extremely high precision with a raceway roundness error of ≤0.001mm a surface roughness Ra of ≤0.1μm and radial clearance strictly controlled within 0.01-0.05mm.
3. Applications
Rolling bearings are suitable for medium-to-high-speed medium-to-light-load and high-precision rotating equipment such as motors (1000-3000 rpm) machine tool spindles (5000-20,000 rpm) automotive transmissions water pumps and fans with typical models including deep groove ball bearings (for pure radial load) and tapered roller bearings (for radial and axial loads).
II. Sliding Bearings
1. Definition and Core Features
Sliding bearings realize rotation through sliding friction between the shaft journal (rotating portion of the shaft) and the bearing bushing (fixed portion) with no rolling elements and they are categorized by force direction into "radial bearings" (carrying radial loads) and "thrust bearings" (carrying axial loads). They have a simple structure and strong impact resistance making them suitable for low-speed heavy-load applications.
2. Structure and Materials
The core components of sliding bearings consist of a bearing housing (made of cast iron or cast steel) and a bearing bushing (inset or cast into the bearing housing with material selected according to operating conditions such as babbitt alloy for low-speed heavy-load applications copper alloy for high-speed light-load applications and engineering plastic for corrosion-resistant applications) and some models include an oil groove/hole for lubricating oil injection. The clearance between the shaft journal and the bearing bushing of sliding bearings must be precisely controlled usually 0.001-0.002 times the shaft journal diameter (e.g., 0.05-0.1mm for a 50mm shaft journal) and scraping and grinding processes are required to ensure accurate fit.
3. Application Scenarios
Sliding bearings are suitable for low-speed heavy-load and impact-vibration equipment such as rolling mill rolls (50-500 rpm) turbine main shafts (100-300 rpm) steam turbines large generators and crushers and they can cushion shocks through the lubricating oil film to extend equipment service life.
III. Thrust Bearings
1. Definition and Core Features
Thrust bearings are a type of bearing specially designed to bear axial loads (loads parallel to the shaft centerline such as axial thrust of the shaft and axial pressure of equipment) and they can be categorized by friction mechanism into "thrust rolling bearings" and "thrust sliding bearings". They are usually used in conjunction with radial bearings to jointly bear the radial and axial loads of the shaft.
2. Structure and Materials
Thrust rolling bearings consist of a locking ring (interference fit with the shaft) a loose ring (fixed to the bearing housing) rolling elements (thrust balls thrust rollers) and a retaining cage where the rolling elements are arranged in a ring and can only bear axial loads but not radial loads. Thrust sliding bearings consist of a thrust bushing (in contact with the shaft mostly made of babbitt alloy or copper alloy) and a bearing housing and they are similar in structure to radial sliding bearings relying on a lubricating oil film to reduce sliding friction and being able to bear greater axial loads.
3. Applications
Thrust rolling bearings are suitable for medium-to-high-speed and moderate axial load scenarios such as automotive clutches axial positioning of machine tool spindles and axial force balancing in centrifugal pumps. Thrust sliding bearings are suitable for low-speed and high-axial load scenarios such as axial support for large hydro turbines and steam turbines and axial positioning in rolling mills.