Cylindrical Roller Bearings are bearing in which cylinders are used as the rolling elements as opposed to balls in ball bearings. As such, the rollers have a greater (linear) contact area with the outer ring and are distribute loads across a broader surface. Subsequently, they have a relatively high radial load capacity and are suitable for high speeds. Double-row cylindrical roller bearings have high radial rigidity and are used primarily for precision machine tools.

Depending on the series as defined below a number of cylindrical roller bearings have no ribs on either the inner or outer ring, so the rings can move axially relative to each other which can be used as free-end bearings.

Pressed steel (with or without tins or fins) or machined brass cages are generally used, but sometimes molded polyamide cages are also available depending on the application. Cylindrical Roller Bearings are also available without cages with a full complement of rollers. This allows even higher loads but at the expense of speed.

Single row cylindrical roller bearings are also manufactured with snap ring grooves on the outer rings. This design simplifies the bearing joint as the bearings are located into the housing by means of the snap rings.

There are different types designated NU, NJ, NUP, N, NF for single-row bearings, and NNU, NN for double-row bearings depending on the design or absence of side ribs. AST’s cylindrical roller bearings come in the following series with various cage designs and Metric dimensions:

N Series - Bearings of N design are single row cylindrical roller bearing and have two fixed ribs on the inner ring that retain the rollers and cage and one smooth outer ring. This design allows an axial displacement in certain limits, of the shaft in relation to the housing. Therefore, N Series rolling bearings are used in non-locating bearing units. Also, the N Series bearings have virtually no thrust capacity.
NU Series - Are single row cylindrical roller bearings and have two fixed ribs on the outer ring and one smooth inner ring. This design allows an axial displacement in certain limits, of the shaft in relation to the housing. Therefore, NU Series rolling bearings are used in non-locating bearing units. Also, the NU Series bearings have no virtually thrust capacity.
NJ Series - Are single row cylindrical roller bearings and have two fixed ribs on the outer ring and a fixed rib on the inner ring which can guide the shaft in a single direction (axially).
NUP Series - Are single row cylindrical roller bearings and have two fixed ribs on the outer ring and, on the inner ring, a fixed rib and a support washer. This way they can be used as locating bearings, guiding the shaft axially in both directions.
RNU Series - Are single row cylindrical roller bearings and have two fixed ribs on the outer ring and has no inner ring. Instead, it uses the shaft as the opposing raceway.
NF Series - Also able to carry incidental thrust loads, this bearing type features two integral ribs on the inner ring and a single rib on the outer ring.
NN Series - Bearings of NN design are double row cylindrical roller bearing and have three fixed ribs on the inner ring that retain the rollers and cage and one smooth outer ring. This design allows an axial displacement in certain limits, of the shaft in relation to the housing. Therefore, N Series rolling bearings are used in non-locating bearing units. Also, the NN Series bearings have no virtually thrust capacity.
NNU Series - Are double row cylindrical roller bearings and have three fixed ribs on the outer ring and one smooth inner ring. This design allows an axial displacement in certain limits, of the shaft in relation to the housing. Therefore, NU Series rolling bearings are used in non-locating bearing units. Also, the NNU Series bearings have no virtually thrust capacity.

NN Series Super Precision Cylindrical Roller Bearings are designed specifically to handle large radial loads in high-speed spindle applications that demand high running accuracy (runout) of bearing-spindle arrangements.
Features
This lineup of bearing includes a basic series that meets ISO standards and a specified series targeting machine tools.
A double-row cylindrical roller bearing series is available for applications requiring high rigidity. A single-row cylindrical roller bearing series is available for applications requiring high-speed performance.
A Robust series of high performance bearings is available for applications requiring both high-speed and high-rigidity performance.