Cylindrical Roller Bearings
Home / Products / Rolling Mill Bearings / Cylindrical Roller Bearings / Double row cylindrical roller bearingsProduct Description
NEWORLD double row cylindrical roller bearings are available in several designs with a cylindrical or tapered bore. The NEWORLD standard assortment presented in this section includes:
● NNU design bearings (fig. 1)
● NN design bearings (fig. 2)
● NNUP design bearings (fig. 3)
Bearing design
Basic design bearings
NEWORLD basic design double row cylindrical roller bearings are available in several designs. The major design differences between the bearings are the configuration of the inner and outer ring flanges and the cage design and material. The most popular designs are:
| Bearing design | Flange configurations | Cage design |
NNU design  | · outer ring: three integral · inner ring: none | · one cage · machined brass or steel · double prong-type · roller centred |
NNU.1 design | · outer ring: three integral · inner ring: none | · two cages · machined brass · window-type · roller centred |
NNU.2 design | · outer ring: one integral central and two loose · inner ring: none | · one cage · machined brass or steel · double prong-type · roller centred |
NNU.3 design | · outer ring: three integral · inner ring: none | · two cages · machined steel · pin-type · pierced rollers |
NNU.4 design | · outer ring: one integral central and two loose · inner ring: none | · two cages · machined steel · pin-type · pierced rollers |
NNU.5 design | · outer ring: two integral · inner ring: none | · one cage · machined brass · window-type · roller centred |
NNU.6 design | · outer ring: two integral · inner ring: none | · one cage · machined steel · pin-type · pierced rollers |
NNU.7 design | · outer ring: one integral and one loose · inner ring: none | · one cage · machined brass · window-type · roller centred |
NNUB design | · outer ring: three integral · extended inner ring: none | · one cage · machined brass or steel · double prong-type · roller centred |
NNUB.1 design | · outer ring: one integral central and two loose · extended inner ring: none | · one cage · machined brass or steel · double prong-type · roller centred |
NNUB.2 design | · outer ring: two integral · extended inner ring: none | · one cage· machined brass · window-type · roller centred |
NNUB.3 design | · outer ring: two integral · extended inner ring: none | · one cage · machined steel · pin-type · pierced rollers |
NNUB.4 design | · outer ring: three integral · extended inner ring: none | · two cages · machined brass · window-type · roller centred |
NNUB.5 design | · outer ring: one integral central and two loose · extended inner ring: none | · two cages · machined steel · pin-type · pierced rollers |
NNUP design | · outer ring: three integral · inner ring: one integral and two loose | · one cage · machined brass or steel · double prong-type · roller centred |
NNUP.1 design | · outer ring: two integral and one loose · inner ring: one integral and one loose | · two cages · machined steel · pin-type · pierced rollers |
NN design | · outer ring: none · inner ring: three integral | · one cage · machined brass or steel · double prong-type · roller centred |
NN.1 design | · outer ring: none · inner ring: three integral | · two cages · either PA66 or stamped steel · window-type· roller centred |
NN.2 design | · outer ring: none · inner ring: three integral | · two cages · machined steel · pin-type · pierced rollers |
NN.3 design | · outer ring: none · inner ring: one integral and two loose | · two cages · machined steel · pin-type · pierced rollers |
Bearing features
Variants/features
Where double row cylindrical roller bearings are to be mounted with a loose fit on the shaft or roll neck (e.g. to allow rapid roll changes) they can be supplied with one or more additional features (fig. 1) to compensate for disadvantages of the loose fit. The helical groove in the bore and/or lubrication grooves in the side faces of the bearing rings enable effective lubrication to be provided for the sliding contact surfaces.
Bearings equipped with one or more of these features are identified in the Design variant/feature (data table) as described in the following:
| G | Helical groove in inner ring bore |
| K | Tapered bore = taper 1:12 for K = taper 1:30 for K30 |
| W | Lubrication grooves in the side faces of the bearing rings |
| WI | Lubrication grooves in the side faces of the inner ring |
| WO | Lubrication grooves in the side faces of the outer ring |
| W20 | Lubrication holes in outer ring |
| W33 | Annular groove and lubrication holes in outer ring |
Features and benefits
● High load carrying capacity
Because of their second row of rollers, double row cylindrical roller bearings are suitable for heavy
radial loads.
● Low friction (Roller end / flange contact area)
The open flange design (fig. 2), together with the roller end design and surface finish, promote
lubricant film formation resulting in lower friction and higher axial load carrying capacity.
● Long service life
The logarithmic roller profile reduces edge stresses at the roller/raceway contact (fig. 3) and sensitivity
to misalignment and shaft deflection.
● Enhanced operational reliability
The surface finish on the contact surfaces of the rollers and raceways supports the formation of a
hydrodynamic lubricant film.
● Separable and interchangeable
The separable components of SKF double row cylindrical roller bearings are interchangeable. This
facilitates mounting and dismounting, as well as maintenance inspections.
● High speed capability
The cage designs are suitable for high speeds, rapid accelerations and peak loads.
Cages
Matched bearings
● are combined so that any difference in cross-sectional height of the bearings used in a matched set
lies within a very small tolerance range. This tighter tolerance is a precondition for equal load sharing
between the bearings.
● can be supplied as:
o sets of two bearings (designation suffix DR)
o sets of three bearings (designation suffix TR)
o sets of four bearings (designation suffix QR)
Cages
NEWORLD double row cylindrical roller bearings are fitted with one or two of the cages shown in table 1.
When used at high temperatures, some lubricants can have a detrimental effect on polyamide cages.
 |  |  |  |  |  |  |  | |
| Cage type | Window- type, roller centred | Window-type, roller centred | Pin-type, pierced rollers | Window-type, roller centred | Double prong-type, roller centred | Double prong-type, roller centred | Window-type, roller centred | Pin-type, pierced rollers |
| Material | PA66, glass fibre reinforced | Stamped steel | Machined steel | Machined brass | Machined brass | Machined steel | Machined brass | Machined steel |
| No. per bearing | 2 | 2 | 2 | 2 | 1 | 1 | 1 | 1 |
Temperature limits
The permissible operating temperature for cylindrical roller bearings can be limited by:
● the dimensional stability of the bearing rings and rollers
● the cage(s)
● the lubricant
Where temperatures outside the permissible range are expected, contact NEWORLD.
Bearing rings and rollers
NEWORLD cylindrical roller bearings are heat stabilized up to 150 °C (300 °F).
Cages
Steel or brass cages can be used at the same operating temperatures as the bearing rings and rollers. For temperature limits of polymer cages, refer to Polymer cages.
Application
Application:
● Motors
● Electricity generators
● Internal combustion engines
● Gas turbines
● Machine tool spindles
● Deceleration devices
● Unloading and lifting machines
● Power generation
● Oil field
● Mining and aggregate
● Processing
● Gear drives
● Rolling mills
