Bearings

Bearings & Accessories

Bearings support & guide rotating or oscillating machine elements – such as shafts, axles or wheels – and transfer loads between machine components. They provide high precision and low friction and therefore enable high rotational speeds while reducing noise, heat, energy consumption and wear. Rolling bearings are cost-effective and exchangeable machine elements that typically follow national or international dimension standards.

SKF manufactures a wide range of ball & roller bearings & Accessories suitable for a variety of applications and types are listed below. Detailed Catalogue can be downloaded by clicking on the line below for each type

• Deep Groove Ball Bearings
• Insert Bearings (Y-Bearing Units)
• Angular Contract Ball Bearings
• Self Aligning Ball Bearings
• Thrust Ball Bearings
• Cylindrical Roller Bearings
• Needle Roller Bearings
• Taper Roller Bearings
• Spherical Roller Bearings
• CARB Toroidal Roller Bearings
• Cylindrical Roller Thrust Bearings
• Needle Roller Thrust Bearings
• Spherical Roller Thrust Bearings
• Cam Rollers
• Support Rollers
• Cam Followers
• Sensor Bearing Units
• High-Temperature Bearings
• Solid Oil Bearings
• INSOCOAT Bearings
• Hybrid Bearings
• NoWear Coated Bearings
• Spherical Roller Plain Bearings
• Adaptor Sleeve
• Withdrawal Sleeves
• Locknut
• Super Precision Bearings
• Plummer blocks –Standard, Customized
• Copper Split Bearing with Plummer block
• Slewing Ring Bearing

These bearings are manufactured in the straight bore, taper bore. Some bearings are provided with different types of seals for dirt protection and supplied with factory-filled greases. Application-specific greases are also available in the bearings

Application-specific bearings are also available in SKF range like for High Temperature, Variable Frequency drive motors

For bearings that are not used in general applications, a Detailed technical datasheet can be provided by us based on a request to Vashi Team.

Bearing Cages

Given the specific functional demands and quantity of bearings being manufactured, the material and manufacturing methods are chosen to provide the most reliable and cost-effective cage.

Cages are mechanically stressed during bearing operation by frictional, impact, centrifugal and inertial forces. They can also be chemically influenced by certain organic solvents or coolants, lubricants, and lubricant additives. Therefore, the material type used for a cage has a significant influence on the suitability of a rolling bearing for a particular application.

Steel cages 

Steel cages can be used at operating temperatures up to 300 °C (570 °F).

Sheet steel cages

Stamped sheet steel cages are made of low carbon steel. These lightweight cages have relatively high strength and, for some bearing types, can be surface treated to further reduce friction and wear in critical conditions.

Machined steel cages

Machined steel cages are normally made of non-alloyed structural steel. To reduce friction and wear, some machined steel cages are surface treated.

Machined steel cages are not affected by the mineral or synthetic oil-based lubricants normally used for rolling bearings, or by the organic solvents used to clean bearings.

They are designated by J, CA and ECA suffix. In the case of Ball bearings, if the designation doesn’t have any cage details, then it is defaulting a stamped steel cage.

Brass cages

Brass cages can be used at operating temperatures up to 250 °C (480 °F).

Sheet brass cages

Stamped sheet brass cages are used for some small and medium­-size bearings. In applications such as refrigeration compressors that use ammonia, machined brass or steel cages should be used.

Machined brass cages

Most brass cages are machined from cast or wrought brass. They are unaffected by most common bearing lubricants, including synthetic oils and greases, and can be cleaned using organic solvents.

Brass cages are designated by M, ML, MA in a majority of the cases.

Polymer cages

Polyamide 66

Polyamide 66 (PA66) is the most commonly used material for injection moulded cages. This material, with or without glass fibres, is characterized by a favourable combination of strength and elasticity. The mechanical properties, such as strength and elasticity, of polymer materials are temperature dependent and subject to ageing. The factors that most influence the ageing process are temperature, time and the medium (lubricant) to which the polymer is exposed. shows the relationship between these factors for glass fibre reinforced PA66. Cage life decreases with increasing temperature and the aggressiveness of the lubricant.

Therefore, whether polyamide cages are suitable for a specific application depends on the operating conditions and life requirements. The classification of lubricants into “aggressive” and “mild” is reflected by the “permissible operating temperature” for cages made of glass fibre reinforced PA66 with various lubricants. The permissible operating temperature is defined as the temperature that provides a cage ageing life of at least 10000 operating hours.

Polyamide loses its elasticity at low temperatures. Therefore, cages made of glass fibre reinforced PA66 should not be used in applications where the continuous operating temperature is below –40 °C

Polyamide 46

Glass fibre reinforced polyamide 46 (PA46) is the standard cage material for some small and medium-­size CARB toroidal roller bearings. The permissible operating temperature is 15 °C higher than for glass fibre reinforced PA66.

Polyamide cages are designated by TN9, P in suffixes

Bearing Internal Clearances

What is Internal Clearance in bearing?

The gap between the roller and outer raceway at the top part of the bearing, when the bearing is put vertically on the flat surface is the internal clearance in the bearing.

Every bearing has clearance. This clearance is measured in the form of Radial Clearance & Axial Clearance.

Some bearings are having factory set clearance and cannot be changed, however for some bearing (taper bore and taper roller) the required clearance has to be achieved during mounting.

Once designers select the bearings then they decide on clearance class (value) considering the fits and tolerances on shaft & housing, application speed, application load, shock loads, no of start/stops etc

There are six clearance classes as per ISO

C1 is the lowest clearance value and C5 is the highest clearance value. ISO has determined the value of clearance for all above six classes and there is  clearance value for a particular bearing bore range

In bearing suffix, when no clearance class is mentioned then it is normal clearance bearing

The basic reasons for selecting a particular clearance class in bearings areas

• The clearance in any straight bore bearing is decided as what level of fits would be required on a shaft so that during mounting, the required expansion takes place on the inner ring bore of bearing and the clearance is adjusted/reduced
• During operation, thermal expansion takes place inside the bearing and it further reduces the clearance
• The clearance in bearings also plays a major role in the alignment of the complete shaft system. If the machine is more prone to misalignment then the clearance value has to be considered while selecting the bearing.
• In the case of taper bore bearings, the clearance is adjusted manually to get more service life of bearing and reliability in operations. The clearance in taper bore bearing with adaptor/withdrawal sleeve can be adjusted further
• In the case of taper roller bearings, the clearances are adjusted by preloading the rollers with an outer ring and inner ring. The preloading has to be achieved to get optimum service life of bearings

Bearings clearances value and measuring methods for different types of bearings are mentioned in SKF Rolling Bearing Catalogue.

Clearance value for new manufactured bearing and reduction for achieving the required clearance class is also mentioned in the catalogue.

Bearing Seal design in Deep Groove Ball Bearings

Shields (designation suffixes Z or ZS)

• are primarily intended for applications where the inner ring rotates
• are fitted in the outer ring and form a narrow gap with the inner ring
• are made of sheet steel, or stainless steel for stainless steel bearings • protect from dirt and debris without friction losses
• when it is having shields from both sides it is mentioned as 2Z or 2 ZS and for one side it is mentioned as Z or ZS

Non-contact seals (designation suffix RZ)

• provide better sealing effectiveness than shields
• can be operated at the same speeds as shields
• form an extremely narrow gap with the inner ring shoulder
• are made of sheet steel reinforced NBR (oil- and wear-resistant)
• when it is having shields from both sides it is mentioned as 2RZ and for one side it is mentioned as RZ

Low-friction seals (designation suffixes RSL or RST)

• provide better sealing effectiveness than non-contact seals
• are made of sheet steel reinforced NBR (oil- and wear-resistant)

RSL design

• can be operated at the same speeds as shields
• make virtually no contact with a recess in the inner ring shoulder
• are available for 60, 62, 63 series bearings in two designs, depending on the size

Contact Seals (RSH and RS Type)

• this is contact seals are highly effective in high contamination environment
• these seals are available in nitrile rubber with a sheet steel reinforced
• when it is having shields from both sides it is mentioned as 2RS, 2RS1 or 2RSH and for one side it is mentioned as RS, RS1, RSH