What is a bearing : introduction

Whats is a bearing ?

A bearing is a device that allows two objects to rotate around each other. They are most often found in machines where two elements rotate relative to each other around a fixed axis. There are many varieties of bearings, each with its own advantages and disadvantages.

Ball bearings, roller bearings and thrust bearings (ball, needle, roller) are among the most common references. The range of bearings also includes self-aligning bearings, needle roller bearings, thrust ball bearings, needle roller bearings, roller thrust bearings, needle roller cages, self-aligning ball bearings, spherical roller bearings, freewheels, etc.

How to choose a bearing?

The choice of this product is generally conditioned by the dimensions, speed and loads it must support. These constraints depend on the machine assembly.

Choosing a bearing adapted to the load and speed it must support

Generally, ball bearings can support high speeds and low loads. On the other hand, roller bearings can support higher loads but at lower speeds.

There are two main types of loads:

• The axial load which is a force applied in a direction parallel to the shaft of a rotating object. It is generally used to describe the stress on bearings and can cause them to fail if it is too high.
• Radial load which is a force applied perpendicular to the shaft of a rotating object. It is the most common type of load on bearings and can cause bearing failure if it is too high.
  

Below is a summary diagram
Diagram to download

How to measure your bearing ?

Today, several tools can be used to measure a bearing. However, the most accurate tool, which is the one we recommend, is the caliper. It can measure the inside diameter (d), the outside diameter (D) and the thickness of the bearing (B).

What are the different types of bearings?

There are three main types of bearings: ball bearings, roller bearings and needle bearings.

Ball Bearings

Ball bearings are the most common. A ball bearing has round balls that help keep friction to a minimum, allowing it to rotate at high speeds. This type of bearing supports a radial load and some degree of axial load in both directions simultaneously.  The ranges are segmented into deep groove ball bearings (metric 600 - 6000 - 16000 - 4000 and imperial LJ - MJ - XLJ and KLNJ series), angular contact bearings (metric 3000 - 5000 - 7000 - LB - LJT and LZ series), spherical plain bearings (metric 1000 and 2000 series), thrust ball bearings and high precision bearings  

Deep groove ball bearings

This type of bearing supports a radial load and a certain degree of axial load in both directions simultaneously. Open designs are widely used. Flanged, sealed or flanged designs are also available. The latter can be easily positioned in the axial direction. Double row ball bearings carry more load and are available in single or double seal designs. They are available in a wide range of sizes. In this range of bearings, you have the option of choosing open, watertight, dusttight, increased clearance and many other features. 

Angular Contact Bearings

Designed for high precision and excellent performance at high speeds. Angular contact ball bearings are designed to support combined loads: both axial and radial. Available in single or double row, matched and four-point contact. Angular contact bearings are designed so that the contact angle between the raceways and the balls is formed when the bearing is in use. The main design feature of this type of bearing is that one or both raceways have a relieved shoulder, or are in a higher position than the other. 

Spherical Ball Bearings 

This bearing is available in steel or polyamide cage and is recommended when there is bending of the shaft, and when the alignment between the shaft and the housing is difficult.  The inner ring with balls and cage can roll slightly on the shaft. The outer ring has a spherical raceway whose center coincides with that of the shaft. 

The contact angle is small, so the axial load capacity is small. The permissible dynamic misalignment varies between approximately 4° and 7° (0.07 to 0.12 radian) under normal load. Find in our Itafran.com catalog, the whole metric 1000 and 2000 series with cylindrical or tapered bore under NSK and CMW brands.  

Thrust Ball Bearings

Thrust ball bearings are divided into two types (single or double) depending on the reaction they have to withstand. The first is able to support an axial load in one direction, while the second is able to support it in both directions. Neither is suitable for applications that involve radial loading or high speed rotation. Find the entire 5100 and 5300 series under the NSK, KOYO and CMW brands in our Itafran.com catalog. 

Roller Bearings

Unlike ball bearings, roller bearings use cylindrical rollers and can support significant radial loads. This is because the contact area is much larger than with balls. This product is also very robust and durable. The product lines are segmented into cylindrical roller bearings (N, NU, NUP, NCF, NJ, LRJ, MRJ, MMRJ series), tapered roller bearings (L - M - 21,000 and 30,000 series), spherical roller bearings (21300, 22200, 22300, 23000,23100, 23200, 23900, 24000, 24100 series), high precision bearings and spherical roller thrust bearings.  

Cylindrical roller bearing

Features include shoulder rings, parallel or tapered bore and lubrication holes and grooves. This type of bearing is characterized by a high radial load capacity when the rollers and raceway are in line contact. Our cylindrical bearings are also suitable for heavy radial loads and impact loads. 

Cylindrical roller bearings are characterized by high radial load capacity and moderate thrust load capacity. They contain cylindrical rollers, which are not true cylinders. Instead, they are crowned or relieved at the ends to reduce stress concentrations. This particular geometry results in low friction and allows for high speed applications. 

NU, N, NNU and NN types are suitable as open-end bearings. The NJ and NF types can support limited axial loads in one direction. 
NH and NUP types can be used as fixed-end bearings. 
NH design cylindrical roller bearings consist of NJ design cylindrical roller bearings and HJ design L-shaped thrust collars  
The free rib on the inner ring of an NUP design cylindrical roller bearing should be mounted so that the marked side is on the outside. 

Tapered roller bearings 

This type of bearing is designed so that the cups, cones and rollers have tapered surfaces whose vertices converge at a common point on the bearing axis. This type is suitable for applications involving heavy load or impact. 

Tapered roller bearings consist of an inner ring (cone), outer ring (cup), cage and rollers that are contoured to distribute the load evenly. They have high radial and axial (thrust) load ratings at low to intermediate speeds. With single row bearings, the thrust load capacity is approximately 60% of the radial capacity. Double row bearings have a higher radial load capacity and can support thrust loads in both directions. 

Spherical roller bearings

These are self-aligning bearings and have a high load carrying capacity. Therefore, spherical bearings are suitable for low/medium speed applications that involve heavy or impact loading. They are available with cylindrical or tapered bores and can be supplied with adapter sleeves as well as withdrawal sleeves. 

These bearings are divided into R, RH (R) and RHA types, which differ in their internal structure. Tapered bore bearings can be easily adjusted and removed using a set of adapters and dismounting sleeves. Spherical bearings are unmatched in their high load capacity and shock tolerance, but are limited in speed. Their reliability is proven even in extremes such as high stress applications with low lubrication. The cage guarantees high dimensional and functional accuracy. Their service life can be estimated at twice that of conventional bearings. 

You can find the entire 20,000 series in our Itafran.com catalog under the NSK, KOYO and CMW brands. 
Our bearings are also available with the following options: 

Machined bronze cage ideal for higher speed operation and providing better performance despite low lubrication. 
Asymmetrically arranged roller design reduces sliding friction and decreases the tendency of the roller to skew during operation (R & RR types); this type uses two sets of asymmetric convex rollers separated by a central shoulder of the inner ring.
Symmetrically arranged roller design (RH type) with two rows of slightly longer rollers arranged symmetrically and separated by a thin center guide ring rather than a thick shoulder.
The R and RH models are also available with grease holes and grooves for improved lubrication.
Self-aligning capability compensates for misalignment in two planes.

Spherical roller thrust bearings

Spherical roller thrust bearings are designed to support high axial loads. They can also support a radial load if its value is less than 55% of the supported axial load. These bearings are not suitable for high speeds. These bearings with a spherical bearing surface are self-aligning and can support a few degrees of inclination. They are usually oil lubricated. You can find in our Itafran.com catalog, the whole 29 000 series under the NSK and KOYO brands. 

Needle bearings 

Finally, needle roller bearings are less bulky because they are thinner and can support high speeds while carrying high radial loads. These bearings do not support axial loads (only combined bearings with thrust and needle roller cages can). 

Needle roller bearings are an economical alternative for applications requiring minimal space to carry a given load at a desired speed. We offer a wide range of high quality needle roller bearings in metric and inch sizes, Radial needle roller and cage assemblies, Bushings (pressed sleeve needle roller bearings), Rollers, Thrust and thrust washers and Combination needle roller bearings.  

Radial needle roller and cage assemblies

Needle roller and cage assemblies have a steel cage that provides both inward and outward needle retention. Sizes range from 3 mm to 165 mm bore (0.1181 to 6.4961 inch). 

The design provides maximum cage strength to accommodate the high loads inherent in needle roller bearings. Precise needle guidance through the cage allows these bearings to operate at high speeds. Fiberglass-reinforced polymer cages are also available. They are available with one or two rows of needles. 

Bushings (deep-drawn needle bearings):

Available with bores from 3 mm to 139.7 mm (0.1181 to 5.5000 inch). They are designed to carry radial loads to reduce friction between rotating components. The bushing serves as an outer raceway for the needles. The small cross-section of the needle bearing provides high load carrying capacity in a minimum of space. Needle roller bearings of this type are easy to install by press-fitting into the housing. 

The outer ring is pressed with such precision that it does not require further machining. The bushings can be either through or blind. They are also available with single or double seals. Other options include a unique, matching lubrication hole in the inner ring. 

Rollers

Our rollers are available with studs ranging in diameter from 10 to 130 mm (0.3937 to 5.1180 inches). Hollow models are available in diameters from 10 to 300 mm (0.3937 to 11.816 inches).  The rollers are characterized by their thick outer ring that rolls directly on the raceway. The thickness of the outer rings allows for high load capacity, while minimizing distortion and bending stresses. 

The rollers are designed with large radial outer rings to withstand heavy bearing and shock loads on conveyor and cam-driven equipment. The outer diameters of the outer rings are either profiled or cylindrical. Profiled rollers are designed to mitigate the effects of uneven loading resulting from drift, bending or misalignment during assembly. Pinch rollers are available with or without lip seals or with flanges. The rollers allow mounting without overhang. Many variations are available in single or double row configurations, with needles or rollers joined or with cages. 

Stops and washers 

Our thrust bearings are available from 5 mm to 240 mm (0.1969 to 9.4488 inch) with the needles held in a cage. 

Smaller diameter needle roller bearings have the needles arranged in a star pattern. The cutouts in the cage space them evenly and serve as a guide to keep them in an orbital path. The purpose of these assemblies is to transmit an axial load between two parts rotating relative to each other with a minimum of friction. 

Needle and cage bearing assemblies can also be monocoque with lip washers serving as raceway surfaces for the needle rollers. The washers can be supplied separately or can be mechanically joined to the needle roller bearing assemblies for ease of handling. All types have very small cross sections. If the reinforcing surfaces cannot be used as raceways, hardened washers are available. Thrusters are also available with needle rollers or heavier cylindrical rollers for high load capacity. 

Combination Needle Roller Bearings

Combination bearings consist of a radial bearing (needle roller bearing) and a thrust bearing (needle roller or cylindrical roller bearing). They are available in bore sizes from 5 mm to 70 mm (0.1966 to 2.7559 inch). Some combination bearings are similar to needle roller bearings with the addition of a thrust bearing. Like other needle roller bearings, they can