BEARINGS AND UNITS

A) INTERACTIVE ENGINEERING CATALOGUE

As the world leader in developing new bearing technology for over a century, SKF has developed a unique understanding of rotating equipment and how machine components and industrial processes are interrelated. Today SKF provides a wide range of technologies and products to OEM and aftermarket customers around the world, in every major industry, at each phase of the asset lifecycle.

For product tables, select Bearings, units and housings; Seals; Coupling systems or Power Transmission products.

 

Bearing Technology - Customized or standard?

SKF engineers can work closely with you to deliver new, innovative and cost-effective bearing technology solutions, see our capabilities, discuss your needs and collaborate with experts at the SKF Solution Factory in your area.

 

Full support with advanced services

SKF services range from new machine development and design verification, to reconditioning, Integrated Maintenance Solutions, training and remote monitoring.

SKF Life Cycle Management

Whether for a single asset or an entire plant, SKF combines knowledge, experience, technologies and global service with our manufacturing and distribution network to create and deliver innovative solutions that are sustainable by design..

 

Engineering tools

Find interactive tools to help you select, install and maintain the appropriate products
for your application needs.

 

 

B) DEEP GROOVE BALL BEARINGS

SKF deep groove ball bearings have deep, uninterrupted raceway grooves. These raceway grooves have a close osculation with the balls, enabling the bearings to accomodate radial and axial loads in both directions.

As the world leader in developing new bearing technology for over a century

• simple in design
• non separable
• suitable for high and even very high speeds
• robust in operation, requiring little maintenance

 

SKF also manufactures engineered solutions, including:

• bearings for extreme temperatures
• SKF DryLube bearings
• bearings with Solid Oil
• insulated bearings
• polymer bearings
• NoWear coated bearings
• sensor bearing units

 

 

C) SELF ALIGNING BALL BEARINGS

The self-aligning ball bearing was invented by SKF. It has two rows of balls and a common sphered raceway in the outer ring. The bearings are consequently self-aligning and insensitive to shaft deflections and angular misalignment of the shaft relative to the housing. Additionally, self-aligning ball bearings generate less friction than any other type of rolling bearing, which enables them to run cooler even at high speeds. Self-aligning ball bearings are available with either a cylindrical or tapered bore. Bearings with a tapered bore can be mounted directly on a shaft or on an adapter or withdrawal sleeve.

 

SKF self-aligning ball bearings are available in several designs, including:

• Open, basic design, bearings (fig 1)
• Sealed, with contact seals on both sides (fig 2)
• Open bearings with an extended inner ring (fig 3)

 

D) CYLINDRICAL ROLLER BEARINGS

SKF cylindrical roller bearings are available in many designs, series and sizes. The majority are single row bearings with a cage. High-capacity bearings, single and double row full complement bearings (without a cage) complete the Bearings with a cage can accommodate heavy radial loads, fast accelerations and high speeds. Full complement bearingsincorporate a maximum number of rollers and are therefore suitable for very heavy radial loads at moderate speeds. SKFhigh-capacity cylindrical roller bearings combine the high load carrying capacity of a full complement bearing with the high speed capability of a bearing with a cage.

 

The factors that influence SKF cylindrical roller bearing performance and service life include but are not limited to the following:

• Roller end / flange contact area
• Logarithmic roller profile
• Surface finish
• Interchangeable components

 

The SKF range of cylindrical roller bearings comprises the basic types

• single row cylindrical roller bearings, caged, mainly of the NU, NJ, NUP and N designs (fig 1)
• double row cylindrical roller bearings, caged, mainly of the NNU and NN designs (fig 2)
• multi-row cylindrical roller bearings, caged (fig 3, fig 4)
• single row full complement cylindrical roller bearings, mainly of the NCF and NJG designs (fig 5)
• double row full complement cylindrical roller bearings, mainly of the NNF design (fig 6)
• multi-row full complement cylindrical roller bearings, with four or eight rows of rollers (fig 7).
  

In addition to the standard assortment the comprehensive SKF range of cylindrical roller bearings consists of

• single row high-precision all-steel or hybrid cylindrical roller bearings (fig 8)
• double row high-precision all-steel or hybrid cylindrical roller bearings (fig 9)
• cylindrical roller bearings and bearing units for railway axleboxes (fig 10)
• single row cylindrical roller bearings for traction motors for railway applications
• backing bearings for cold rolling mills of the cluster type (fig 11)
• indexing roller units for continuous furnaces (fig 12).

other cylindrical roller bearings for special applications include a special electrical insulated coating, called INSOCOAT®. Details of these bearings can be found in this catalogue in the section Engineering products.

 

E) SPHERICAL ROLLER BEARINGS

Designs and variants

Spherical roller bearings Spherical roller bearings have two rows of rollers, a common sphered outer ring raceway and two inner ring raceways inclined at an angle to the bearing axis. The centre point of the sphere in the outer ring raceway is at the bearing axis. Therefore, the bearings are self-aligning and insensitive to misalignment of the shaft relative to the housing, which can be caused, for example, by shaft deflection. Spherical roller bearings are designed to accommodate heavyradial loads, as well as heavy axial loads in both directions.

 

Factors that influence SKF spherical roller bearing performance Bearing performance is not only determined by load or speed ratings. There are a number of other factors that contribute to bearing performance. To a large extent,performance is influenced by the geometry of the rollers, raceways and cages, the heat treatment, as well as the surface finish of all contact surfaces.

• Symmetrical rollers
• Roller tolerances
• Special roller profile

 

Assortment

The assortment of SKF spherical roller bearings is the widest on the market and includes standard bearings and application specific bearings. Almost all SKF spherical roller bearings are available with either a cylindrical or tapered bore. The assortment of standard bearings includes:

• open bearings
• sealed bearings
• bearings for vibratory applications
• SKF Energy Efficient (E2) bearings

 

The SKF spherical roller bearings assortment on-line constitutes the basic SKF assortment and is only part of the total assortment. For applications where the bearings are subjected to unique operating conditions, SKF can customize bearings to meet the needs of that particular application. For example, bearings for:

• printing presses, paper mills or coaters in high precision execution
• very arduous operating conditions, e. g. continuous casters
• high temperature applications
• railway vehicles

For additional information about application specific spherical roller bearings, contact the SKF application engineering service.

 

F) ENERGY EFFICIENT (E2) DEEP GROOVE BALL BEARINGS -

After the launch of the SKF Energy Efficient (E2) deep groove ball bearing (DGBB), SKF presents a new sealed deep groove ball bearing which completes the E2 offer. SKF Sealed E2 DGBB reduces frictional losses in a bearing by 30% or more when compared to SKF Explorer bearing.Designed for grease lubricated, light to normal load applications, SKF Sealed E2 DGBB also enables longer bearing service life and is designed to improve application efficiency by reducing bearing power losses. 

 

G) ANGULAR CONTACT BALL BEARINGS

displaced with respect to each other in the direction of the bearing axis. This means that they are designed to accommodate combined loads, i.e. simultaneously acting radial and axial loads.The axial load carrying capacity of angular contact ball bearings increases with increasing contact angle. The contact angle α is defined as the angle between the line joining the points of contact of the ball and the raceways in the radial plane, along which the load is transmitted from one raceway to another, and a line perpendicular to the bearing axis. SKF angular contact ball bearings are produced in a wide variety of designs and sizes. Those commonly used include:

 

• Single row angular contact ball bearings (fig 1)
• Double row angular contact ball bearings (fig 2)
• Four-point contact ball bearings (fig 3)
• Other SKF angular contact ball bearings

Products

 

H) CYLINDRICAL ROLLER THRUST BEARINGS

Cylindrical roller thrust bearings are suitable for arrangements that have to support heavy axial loads. Furthermore, they are relatively insensitive to shock loads, are very stiff and require little axial space. As standard they are available as single direction bearings and can only accommodate axial loads acting in one direction.

 

Cylindrical roller thrust bearings are simple in form and design and are produced in single row (fig 1) and double row (fig 2) designs. The bearings in the 811 and 812 series are mainly used where thrust ball bearings have insufficient load carrying capacity.

 

The cylindrical surface of the rollers is slightly relieved towards the ends. The resulting contact profile virtually eliminates damaging edge stresses. The bearings are of separable design; the individual components can be mounted separately.

Components

For applications where

• the faces of adjacent machine components can serve as raceways and slim bearing arrangements are required or
• other combinations of cylindrical roller and cage thrust assembles and washers are required, e.g. with two shaft or housing washers,

it is possible to order the components

• cylindrical roller and cage thrust assemblies K (fig 3)
• shaft washers WS (fig 4)
• housing washers GS (fig 5)

separately, see product table.

Raceway washers of the LS series (see section Needle roller thrust bearings - Bearing washers) may be used for bearings in the 811 series both as shaft and as housing washers where accurate centring of the washers is not needed or where low speeds are involved.

Double direction bearings

Double direction bearings can easily be assembled by combining appropriate shaft washers in the WS 811 series or housing washers in the GS 811 series with two cylindrical roller and cage thrust assemblies in the K 811 series and a suitable intermediate washer with internal centring (fig 6) or external centring (fig 7).

 

These intermediate washers should have the same quality and hardness as the bearing washers. Recommendations for intermediate washer dimensions will be supplied on request. Guideline values for the dimensional, form and running accuracy are provided in the section Design of associated components.

 

 

I) THRUST BALL BEARING

SKF thrust ball bearings are produced as single direction or double direction thrust ball bearings. They are designed to accommodate axial loads only and must not be subjected to any radial load. SKF thrust ball bearings are separable, i.e. the shaft washer, housing washer(s), ball and cage assembly(s) can be mountedseparately. Shaft washers have a ground bore to enable an interference fit. The bore of the housing washer is turned and always larger than the shaft washer bore.

 

Single direction thrust ball bearing

SKF single direction thrust ball bearings consist of a shaft washer, a housing washer and a ball and cage assembly (fig 1). As their name implies, single direction thrust ball bearings can accommodate axial loads and locate a shaft axially, in one direction only.

 

Double direction thrust ball bearings

SKF double direction thrust ball bearings consist of one shaft washer, two housing washers and two ball and cage assemblies (fig 2). The housing washers and ball and cage assemblies are identical to those found in single direction bearings. Double direction thrust ball bearings can accommodate axial loads and locate a shaft axially, in both directions.

 

To accommodate initial misalignment between the shaft and housing, SKF supplies both single and double direction thrust ball bearings with sphered seat surfaces on the housing washers (fig 3). They can be used together with a sphered seat washer adjacent to the housing washer (fig 4 and fig 5) or adjacent to a machine component manufactured with asphered surface.

Appropriate sphered seat washers must be ordered separately.

 

Depending on the bearing series, they have the basic designation U 2, U 3 or U 4 followed by a two-digit number, which identifies the size (e.g. sphered seat washer U 320 for bearing 53320).

 

J) TAPERED ROLLER BEARINGS

Tapered roller bearings have tapered inner and outer ring raceways and tapered rollers. They are designed to accommodate combined loads, i.e. simultaneously acting radial and axial loads. The projection lines of the raceways meet at a common point on the bearing axis (fig 1) to provide true rolling and low friction. The axial load carrying capacity of tapered roller bearings increases with increasing contact angle (α). The size of the angle is indicated by the calculation factor e († product tables): the larger the value of e, the larger the contact angle. A single row tapered roller bearing is typically adjusted against a second tapered roller bearing.

The factors that influence SKF bearing performance and service life include but are not limited to the following:

• roller end/ flange contact area
• raceways profiles
• consistency of profiles and roller size
• running-in

Tapered roller bearings are produced by SKF in many designs and sizes to match their many uses.
These can be grouped as follows

 

K) SPHERICAL ROLLER THRUST BEARING

SKF spherical roller thrust bearings have specially designed raceways and accommodate a large number of asymmetrical rollers.The rollers have an optimum conformity with the washer raceways to optimize load distribution along the roller length. Therefore, they can accommodate relatively high speeds, heavy axial loads in one direction and heavy radial loads. The load is transmitted between the raceways at an angle to the bearing axis. Spherical roller thrust bearings are self-aligning and insensitive to static misalignment of the shaft relative to the housing.

 

 

L) SLEWING BEARINGS

Robust performance for road rollers and compactors

Manufacturers of road rollers and compactors aim for high-speed, high-quality compacting, which requires high vibration. By meeting these specific demands, SKF slewing bearings provide reliable, highly productive and cost-effective solutions for the drum support and steering pivot. Due to the integrated heavy-duty hub seal, the bearing remains unaffected by the hot asphalt environment and is protected against water intrusion.

 

For drum support applications, slewing bearings enable a very compact solution that eases the road roller configuration to extend its working width. It also enables the road roller to work closer to obstacles, thus improving operator comfort and visibility.

 

For steering pivot applications, our slewing bearings support the vibration frequency and amplitude. The ready-to-install solution also simplifies machine design and saves assembly time.

 

M) Y BEARINGS

Y-bearings, which are usually refer to insert bearings, are based on sealed deep groove ball bearings in the 62 and 63 series, but have a convex outer ring and in most cases an extended inner ringwith a certain locking device enabling quick and easy mounting onto the shaft.

Y-bearings are available singly or as units. Y-bearing units consist of a housing, bearing and seal that is preassembled and greased at the factory. These ready-to-mount units can accommodate moderate initial misalignment (Demo) but normally do not enable axial displacement of the shaft.

 

Y-bearings and Y-bearing units offer a simple, cost-effective solution that can provide a number of benefits.

 

New market offers

 

 

N) Y BEARING UNITS

Standard SKF ball bearing units are referred to as Y-bearing units. These units comprise

• a Y-bearing (insert bearing) which is a single row deep groove ball bearing with convex sphered outside diameter (fig a)
• a Y-bearing housing, which has a correspondingly sphered but concave bore (fig b).

Y-bearing units are ready-to-mount, greased and sealed units which enable initial errors of alignment to be compensated for.

 

Y-bearing units consist of a housing, bearing and seal that is preassembled and greased at the factory. These ready-to-mount units can accommodate moderate initial misalignment but normally do not enable axial displacement of the shaft. Y-bearing units offer a simple, cost-effective solution that can provide a number of benefits.

 

Designs and Variants

Assortment

Y-bearing unit designs
They are available as

• Y-bearing plummer block units (fig c)
• Y-bearing flanged units (fig d)
• Y-bearing take-up units (fig e).

The housings of the units are produced in a variety of designs and different materials

• composite material
• grey cast iron
• sheet steel
• stainless steel

Locking methods

There is a choice of five different methods by which an SKF Y-bearings can can be located onto a shaft:

• Eccentric locking systems
• Concentric locking systems

Superior sealing performance

The seals used in SKF Y-bearing units are designed to meet a variety of industry and application requirements.

 

 

O) BEARING HOUSING

The extensive SKF product range includes a comprehensive selection of bearing housings. This catalogue provides a general view of the SKF range for standard housings and will facilitate the tasks of the designer in selecting the right.

 

The product range table provides an overview of the standard housings and their major features.By specifying the requested criteria the appropriate housing can quickly be found with Housing Select.Many other types of bearing housing not listed in this catalogue and variants of listed housings adapted to customer demands can also be supplied.

 

For application where standard housings are not suitable, SKF can supply special housings of grey cast iron, spheroidal graphite cast iron and cast steel, e.g. for

• paper machines (fig 1)
• conveyor equipment
• rotary kilns (fig 2)
• drums
• tube mills
• converters
• large electrical machines
• rail vehicles (fig 3).

 

 

P) SUPER- PRECISION BEARINGS

Machine tools and other precision applications require superior bearing performance. Extended speed capability, a high degree of running accuracy, high system rigidity, low heat generation, as well as low noise and vibration levels are just some of the challenges.Rolling bearings for general industrial applications can only partly fulfill these requirements. Therefore, SKF manufactures a comprehensive assortment of super-precision bearings.

 

Typical applications for super-precision bearings are:

 

 

Q) SENSOR BEARING UNITS

SKF sensor bearing units are used to accurately monitor the status of rotating or linear components. These units are:

• compact
• robust and reliable
• simple and ready to mount

Following is a brief overview of the sensor integrated solutions engineered by SKF. These solutions have been well proven in a variety of industrial and automotive applications such as electric motors, electric vehicles, road rollers, tractors, forklifts and conveyors.

Typical uses include:

• motor management
• steering
• speed and position sensing
• temperature and vibration sensing
• measurement of angular position

For additional information about SKF sensor bearing units, go to related documents in the menu on the right or contact your local SKF representative.

 

 

R) HYBRID BEARINGS

Hybrid bearings have rings made of bearing steel and rolling elements made of bearing grade silicon nitride (Si3N4). Because silicon nitride is such an excellent electrical insulator, hybrid bearings can be used to effectively insulate the housing from the shaft in both AC and DC motors as well as in generators.

 

In addition to being an excellent insulator, hybrid bearings have higher speed capabilities and provide longer bearing service life under the same operating conditions than same-sized all-steel bearings. Hybrid bearings also perform extremely well under vibrating or oscillating conditions. Often, it is not necessary to preload the bearing or apply a special grease under these conditions.

 

 

S) NOWEAR BEARINGS

NoWear bearings will operate with high reliability, even when adequate surface separation cannot be achieved (κ < 1), by preventing direct metal-to-metal contact between rolling elements and rings.

 

NoWear bearings are still made of steel but the rolling elements, and the raceways if necessary, are coated with a new type of diamond-like carbon which is only a few microns thick. A physical vapour deposition process applies the low friction, ceramic coating. Bearing surfaces coated in this way have all the resilience of the underlying material, but with the hardness, low friction coefficient and wear resistance of the NoWear coating.

 

 

T) INSOCOAT BEARINGS

Electric motors, generators and associated equipment are at risk when an electric current passes through a bearing. This can damage the contact surfaces of rolling elements and raceways in the bearing (electrical erosion) and rapidly degrade the grease. An additional risk in electric motors and generators comes from high frequency currents due to the inherent stray capacitance. The risk of damage increases if the application uses a frequency converter.

INSOCOAT bearings with a coated outer ring

INSOCOAT bearings typically have the outside diameter and side faces of the outer ring coated with aluminium-oxide. These bearings are identified by the designation suffix VL0241.

INSOCOAT bearings with a coated inner ring

INSOCOAT bearings that have the bore and side faces of the inner ring coated are identified by the designation suffix VL2071.

These bearings provide enhanced protection against high frequency electric currents due to the smaller coated surface area of the inner ring compared to the outer ring.

 

Assortment

The standard assortment of INSOCOAT bearings constitutes the most commonly used sizes and variants of:

• single row deep groove ball bearings
• single row cylindrical roller bearings

 

 

U) HIGH TEMPERATURE BEARINGS

SKF high temperature bearings are designed to deliver increased reliability, reduced complexity and decreased environmental impact in operating temperatures up to 350 °C (660 °F). Because SKF high temperature bearings correspond to the ISO dimensions of grease-lubricated bearings, production efficiencies and cost savings can be realized with a simple change to the SKF bearing solution.