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Design variants

SKF double row cylindrical roller bearings of the NNU, NN and NNUP designs differ mainly in the flange configuration but may also vary slightly in design for manufacturing, application or maintenance reasons, e.g. with an extended inner ring or with loose flange rings on the outer ring. The basic designs and their most important variants are described in the following.
For bearing arrangements where the bearings are to be mounted with a loose instead of an interference fit on the shaft or roll neck, e.g. to allow rapid roll changes, a special design of double row bearing is supplied by SKF (fig 1). To alleviate the disadvantage of the loose fit - the inner ring turns on its seat and can cause damage to the bearing and the seat - these special bearings have a helical groove in the bore and/or lubrication grooves in the side faces of the bearing rings. These grooves enable efficient lubrication to be provided for the sliding contact surfaces.
Bearings which exhibit one or more of the features named above are identified in the product table by the following letters:

GHelical groove in inner ring bore
WLubrication grooves in the side faces of the bearing rings
WILubrication grooves in the side faces of the inner ring
WOLubrication grooves in the side faces of the outer ring
W33Annular groove and three lubrication holes in outer ring
The letters appear after the design code in the product table, e.g. NNU.2/W33GW.

NNU design

Outer ring with three integral flanges. Roller guided machined double pronged cage of brass. With or without annular groove and/or lubrication holes in the outer ring (fig 2).

NNU.1 design

Outer ring with three integral flanges. Two roller guided machined brass window-type cages. With or without annular groove and/or lubrication holes in the outer ring (fig 3).

NNU.2 design

Outer ring with integral central flange and two loose flange rings. Roller guided machined double pronged cage of brass. With or without annular groove and/or lubrication holes in the outer ring (fig 4).

NNU.3 design

Outer ring with three integral flanges. Pierced rollers and two steel pin-type cages. With or without annular groove and/or lubrication holes in the outer ring (fig 5).

NNU.4 design

Outer ring with integral central flange and two loose flange rings. Pierced rollers and two steel pin-type cages. With or without annular groove and/or lubrication holes in the outer ring (fig 6).

NNU.5 design

Outer ring with two integral flanges. Double window-type cage of brass. With or without annular groove and/or lubrication holes in the outer ring (fig 7).

NNU.6 design

Outer ring with two integral flanges. Pierced rollers and one double row pin-type cage of steel. With or without annular groove and/or lubrication holes in the outer ring (fig 8).

NNU.7 design

One integral flange on the outer ring and one loose flange ring. Machined brass cage (double row). With or without annular groove and/or lubrication holes in the outer ring (fig 9).

NNUB design

Outer ring with three integral flanges. Extended inner ring. Roller guided double pronged cage of brass. With or without annular groove and/or lubrication holes in the outer ring (fig 10).

NNUB.1 design

Outer ring with integral central flange and two loose flange rings. Extended inner ring. Roller guided double pronged cage of brass. With or without annular groove and/or lubrication holes in the outer ring (fig 11).

NNUB.2 design

Outer ring with two integral flanges. Extended inner ring. Double row window-type cage of brass. With or without annular groove and/or lubrication holes in the outer ring (fig 12).

NNUB.3 design

Outer ring with two integral flanges. Extended inner ring, Pierced rollers and one double-row pin-type cage of steel. With or without annular groove and/or lubrication holes in the outer ring (fig 13).

NNUB.4 design

Outer ring with three integral flanges. Extended inner ring. Two roller guided window-type cages of brass. With or without annular groove and/or lubrication holes in the outer ring (fig 14).

NNUB.5 design

Outer ring with central integral flange and two loose flange rings. Extended inner ring. Pierced rollers and two pin-type cages of steel. With or without annular groove and/or lubrication holes in the outer ring (fig 15).

NNUP design

Outer ring with three integral flanges. One integral flange and one loose flange ring on the inner ring. Roller guided double pronged cage of brass. Annular groove and lubrication holes in the outer ring (fig 16).

NNUP.1 design

Outer ring with two integral flanges and a loose flange ring. One integral flange and one loose flange ring on the inner ring. Pierced rollers and two pin-type steel cages (fig 17).

NN design

Inner ring with three integral flanges. Roller guided double pronged cages of brass. Annular groove and lubrication holes in the outer ring (fig 18).

NN.1 design

Inner ring with three integral flanges. Two roller guided cages of polyamide 66 or pressed steel. Annular groove and lubrication holes in the outer ring (fig 19).
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