SKF NN 3011 KTN/SPW33 55x90x26 mm - Super-Precision Double-Row Cylindrical Roller Bearing

SKF NN 3011 KTN/SPW33 55x90x26 mm - Super-Precision Double-Row Cylindrical Roller Bearing

SKF NN 3011 KTN/SPW33 is a super-precision double-row cylindrical roller bearing measuring 55x90x26 mm, with a 1:12 tapered bore, non-metallic cage, SP precision class and W33 lubrication features. The NN 30 design provides high radial stiffness and permits axial displacement between the shaft and housing. SKF NN3011 K.TNSPW33 is an older designation format encountered on bearings and in technical documentation.

Technical data - SKF NN 3011 KTN/SPW33

SKF NN 3011 KTN/SPW33 and NN3011 K.TNSPW33

Two designation formats may be encountered for this SKF bearing:

SKF NN 3011 KTN/SPW33

and:

SKF NN3011 K.TNSPW33

The NN3011 K.TNSPW33 format can be encountered as an older form of the designation on bearings, packaging and technical documentation, while current SKF catalogue references use:

NN 3011 KTN/SPW33

When the manufacturer, dimensions and complete bearing execution correspond, these designations should not be treated as two separate bearing models.

Keeping both forms in the product description is useful for identifying older bearings and for users searching by the designation marked on an existing component.

What does SKF NN 3011 KTN/SPW33 mean?

The complete designation contains important information about the bearing design.

NN - double-row cylindrical roller bearing design with three integral flanges on the inner ring and a flangeless outer ring.

3011 - identifies the dimension series and bearing size.

Bore code 11 corresponds to a nominal bore diameter of:

55 mm

K - tapered bore with a 1:12 taper.

TN - identifies the non-metallic cage execution.

SP - SKF special precision class used for super-precision cylindrical roller bearings.

W33 - annular groove and lubrication holes in the outer ring.

Each part of the designation is relevant when identifying or replacing the bearing.

SKF NN 3011 KTN/SPW33 dimensions

The principal dimensions are:

55x90x26 mm

where:

• d = 55 mm - bore diameter

• D = 90 mm - outside diameter

• B = 26 mm - bearing width

These are the principal mounting dimensions.

However, matching dimensions alone do not establish complete interchangeability.

For SKF NN 3011 KTN/SPW33, the following characteristics must also be considered:

• NN internal design

• double-row roller arrangement

• K tapered bore

• 1:12 bore taper

• TN cage execution

• SP precision class

• W33 lubrication features

Double-row NN design

SKF NN 3011 KTN/SPW33 contains two rows of cylindrical rollers.

In the NN design:

• the inner ring has three integral flanges

• the outer ring has no flanges

• two rows of cylindrical rollers operate between the rings

This geometry is particularly suitable for precision bearing arrangements requiring high radial stiffness.

Why are two rows of cylindrical rollers used?

Cylindrical rollers provide line contact with the raceways.

This allows cylindrical roller bearings to achieve high radial load carrying capability and high radial stiffness.

The double-row arrangement further increases the stiffness of the bearing system.

These characteristics are especially important in precision spindle arrangements where radial displacement of the shaft must be minimized.

NN design and axial displacement

One of the key characteristics of the NN design is its flangeless outer ring.

This allows axial displacement between the bearing rings within the bearing itself.

Such displacement can accommodate changes in the relative axial position of the shaft and housing, for example those resulting from thermal expansion of the shaft.

For this reason, an NN bearing can function as the non-locating bearing in an appropriately designed bearing arrangement.

It should not be considered a conventional bearing for axial location of the shaft.

What does K mean?

The suffix K means:

tapered bore, taper 1:12

This is one of the most important characteristics of SKF NN 3011 KTN/SPW33.

The bearing does not have a conventional cylindrical bore.

The tapered bore enables controlled mounting of the inner ring on a corresponding tapered shaft seat.

Why is the tapered bore important?

As the bearing is driven further onto the tapered shaft seat, the inner ring expands.

This changes the radial internal clearance of the bearing.

Controlled mounting therefore allows the required operating condition of the bearing arrangement to be established.

This is particularly important for super-precision cylindrical roller bearings used in spindle systems.

Incorrect mounting can result in:

• excessive reduction of radial clearance

• excessive remaining clearance

• increased operating temperature

• incorrect bearing stiffness

• reduced running accuracy

• reduced bearing service life

The K execution therefore requires a controlled mounting procedure.

What does TN mean?

The TN element identifies the cage execution.

For this bearing execution, SKF specifies a non-metallic cage.

The cage performs several important functions:

• maintains the correct spacing between rollers

• guides the rolling elements

• prevents direct contact between adjacent rollers

• supports stable operation of both roller rows

The cage execution forms part of the complete technical specification of a super-precision cylindrical roller bearing.

Therefore, TN should not be ignored when identifying a replacement.

What does SP mean?

SP identifies an SKF special precision class for super-precision cylindrical roller bearings.

Precision is particularly important in bearing arrangements where the following characteristics are critical:

• running accuracy

• radial runout

• precise shaft guidance

• system stiffness

• stable high-speed operation

• spindle performance

For this reason:

SKF NN 3011 KTN/SPW33

should not be reduced simply to:

SKF NN 3011

The SP designation is an important part of the bearing specification.

What does W33 mean?

The suffix W33 identifies an execution with:

an annular groove and lubrication holes in the outer ring

This arrangement enables lubricant to be supplied through an appropriately designed housing lubrication system.

W33 is a physical feature of the outer ring.

A W33 bearing should therefore not automatically be replaced by an execution without W33 solely because the principal dimensions are identical.

High radial stiffness

High radial stiffness is one of the major characteristics of SKF NN 30 double-row cylindrical roller bearings.

It results from:

• cylindrical rolling elements

• line contact between rollers and raceways

• two rows of rollers

• NN bearing geometry

This is particularly important in precision systems where small radial shaft movements can affect machining accuracy or spindle performance.

Radial loads

SKF NN 3011 KTN/SPW33 is designed primarily to accommodate:

radial loads

The cylindrical rollers and double-row arrangement provide a large effective contact area between the rolling elements and raceways.

The NN design is not intended to provide conventional axial location of the shaft.

In a spindle arrangement, axial loads and shaft location are normally handled by other bearings selected according to the complete bearing system design.

SKF NN 3011 KTN/SPW33 vs NN3011 K.TNSPW33

Both designation formats may be encountered:

NN 3011 KTN/SPW33

and:

NN3011 K.TNSPW33

The first is the current catalogue-style designation.

The second is an older designation format that may be encountered on older bearings, packaging, technical drawings, maintenance records and commercial documentation.

Where the manufacturer, dimensions and complete execution correspond, there is no technical reason to create two separate product identities solely because of this formatting difference.

The older designation should nevertheless be retained as an alternative search reference because users frequently identify replacement bearings from markings found on an existing component.

SKF NN 3011 KTN/SPW33 vs standard NN 3011

The basic designation:

NN 3011

does not describe all characteristics of this bearing.

The complete designation:

NN 3011 KTN/SPW33

additionally identifies important features including:

• K - tapered bore

• TN - cage execution

• SP - special precision class

• W33 - lubrication groove and holes

A standard NN 3011 should therefore not automatically be considered a complete replacement.

SKF NN 3011 KTN/SPW33 vs cylindrical-bore NN 3011

The K execution has a 1:12 tapered bore.

An execution without K has a different bore geometry.

This difference affects:

• shaft seat geometry

• mounting procedure

• inner-ring mounting position

• adjustment of radial internal clearance during mounting

Consequently, identical 55x90x26 mm principal dimensions do not make tapered-bore and cylindrical-bore executions automatically interchangeable.

Alternative designations and search references

This bearing may be searched for under several designation formats:

• SKF NN 3011 KTN/SPW33

• NN 3011 KTN/SPW33 SKF

• SKF NN3011 KTN/SPW33

• NN3011 KTN/SPW33

• SKF NN3011 K.TNSPW33

• NN3011 K.TNSPW33 SKF

• SKF NN 3011 K.TNSPW33

• NN 3011 K.TNSPW33

• SKF NN3011 K TNSPW33

• NN3011 K TNSPW33

• SKF NN3011 SP

• SKF NN3011 W33

• SKF NN3011 55x90x26

• NN3011 55x90x26

• SKF NN3011 super precision

• SKF NN3011 double row cylindrical roller bearing

• SKF NN3011 spindle bearing

For unambiguous technical identification, the preferred designation is:

SKF NN 3011 KTN/SPW33

while:

SKF NN3011 K.TNSPW33

should be retained as an older designation/search reference.

How to select a replacement for SKF NN 3011 KTN/SPW33

Before selecting a replacement, verify:

• manufacturer

• complete designation

• NN design

• double-row roller arrangement

• dimensions 55x90x26 mm

• K tapered bore

• 1:12 bore taper

• TN cage execution

• SP precision class

• W33 lubrication execution

• required radial clearance after mounting

• shaft mounting arrangement

• lubrication system

• radial load

• operating speed

• shaft accuracy

• housing accuracy

Matching 55x90x26 mm dimensions alone does not guarantee interchangeability.

For super-precision bearings, the complete designation and all relevant design features must be checked.

Applications

SKF NN 30 series super-precision double-row cylindrical roller bearings are used in bearing arrangements requiring high radial stiffness and accurate shaft guidance.

Typical applications for this bearing family include:

• machine tool spindles

• lathe spindles

• milling machines

• grinding machines

• machining centres

• precision rotating assemblies

• systems requiring high radial stiffness

These are typical applications of the NN 30 super-precision bearing family.

They do not confirm the suitability of the exact SKF NN 3011 KTN/SPW33 for a particular machine.

For replacement in a specific spindle or machine, the equipment manufacturer's technical documentation should be checked.

Mounting SKF NN 3011 KTN/SPW33

A super-precision cylindrical roller bearing with a tapered bore requires accurate and controlled mounting.

Before installation:

• maintain very high cleanliness

• inspect the bearing

• check the tapered shaft seat geometry

• inspect locating surfaces

• protect raceways and rollers against damage

• use suitable mounting equipment

During mounting, the axial drive-up of the inner ring on the tapered seat and the resulting radial internal clearance must be carefully controlled.

Uncontrolled mounting forces should not be transmitted through the rollers and raceways.

After installation, the bearing must receive the lubrication specified for the particular bearing arrangement.

FAQ

What are the dimensions of SKF NN 3011 KTN/SPW33?

The bearing measures 55x90x26 mm: 55 mm bore, 90 mm outside diameter and 26 mm width.

Are SKF NN 3011 KTN/SPW33 and NN3011 K.TNSPW33 the same bearing?

Where the manufacturer, dimensions and complete execution correspond, these designations identify the same bearing execution. NN3011 K.TNSPW33 is an older designation format, while NN 3011 KTN/SPW33 is used in newer SKF catalogue references.

What type of bearing is SKF NN 3011 KTN/SPW33?

It is a super-precision double-row cylindrical roller bearing.

What does K mean?

K identifies a tapered bore with a 1:12 taper.

What does TN mean?

TN identifies the non-metallic cage execution.

What does SP mean?

SP identifies an SKF special precision class used for super-precision cylindrical roller bearings.

What does W33 mean?

W33 identifies an annular groove and lubrication holes in the outer ring.

Can SKF NN 3011 KTN/SPW33 accommodate axial loads?

The NN design is intended primarily for radial loads and permits relative axial displacement between the bearing rings. It is not a conventional locating bearing for axial shaft location.

Can any NN3011 55x90x26 bearing replace it?

No. The complete designation must be checked, particularly the K tapered bore, cage execution, SP precision class, W33 features and mounting requirements.

SKF NN 3011 KTN/SPW33 - key information

SKF NN 3011 KTN/SPW33 is a super-precision double-row cylindrical roller bearing measuring 55x90x26 mm, with a 1:12 K tapered bore, TN cage execution, SP precision class and W33 lubrication groove and holes. The older NN3011 K.TNSPW33 designation should also be considered when identifying or searching for this bearing.

SKF NN 3011 KTN/SPW33 is available from the specialist industrial supplier simmering.pl, with stock in Poland and worldwide shipping. Assistance is also available for identifying older SKF designations and selecting the correct super-precision bearing execution.