NNF Double Row Full Complement Cylindrical Roller Bearings: Structure, Applications and Selection

Published 2026-10-31 - RAYSDE Bearing - Supplier and OEM

NNF bearings are double row, full complement cylindrical roller bearings built for very high radial loads at moderate speeds. They appear wherever a compact envelope must carry heavy radial load with high rigidity: wind turbine gearboxes, planetary reducers, industrial gearboxes, cranes and roll systems. This guide explains the structure, where NNF bearings are used, and how to select one.

1. What NNF means

In common designation practice, NNF identifies a double row, full complement cylindrical roller bearing. Two rows of rollers run between outer ring flanges and the design has no cage. Removing the cage lets the bearing hold the maximum number of rollers for its envelope, which is why radial load capacity and rigidity are high. The trade-off is speed: without a cage, adjacent rollers touch and generate more friction and heat, so the permissible speed is lower than for a caged bearing of the same size.

2. Structure and load path

Rollers are guided between flanges on the outer ring, and load is shared across two rows rather than one. This doubles the number of load carrying contact lines compared with a single row design of similar width, which is the main reason radial capacity is so high. Many NNF designs use a separable inner ring, which simplifies mounting and dismounting during gearbox service. Outer rings are frequently supplied with lubrication grooves and lubrication holes so that grease or oil reaches both rows, and sealing options are available for contaminated environments.

3. Typical applications

• Wind turbine gearboxes. Planetary and parallel stages, planet carrier supports and output shafts, where radial load is high and speed is moderate.
• Planetary reducers and industrial gearboxes. NNF bearings suit compact reducers that must transmit high torque in a limited envelope.
• Cranes, hoists and winches. Shock radial loads and slow to moderate rotation favour a full complement design.
• Roll systems. Leveller and straightener rolls in plate mills carry heavy radial load; see our leveller roll bearing case.

4. Full complement versus caged

The choice comes down to load against speed. Full complement delivers maximum radial capacity and rigidity but a lower permissible speed. A caged design sacrifices some capacity for higher speed and lower friction. For a detailed side by side comparison, including capacity and speed curves and a selection checklist for crushers and heavy gearboxes, read our full complement versus caged comparison.

5. Selection checklist

Before specifying an NNF bearing, work through these points:

• Radial load. Magnitude and direction, plus any shock or vibration peaks.
• Speed. Confirm the permissible speed for the full complement design at your load and lubrication, not the caged figure.
• Lubrication. Grease or oil, relubrication intervals, and whether the outer ring has lubrication grooves and holes.
• Sealing. Open or sealed, depending on contamination and moisture.
• Fits. Shaft and housing tolerances, and which ring carries the interference fit.
• Temperature. Operating range and any clearance implications.
• Dimensions. Take exact boundary dimensions and load ratings from the product page or by inquiry. Do not estimate them.

6. Installation and maintenance

Mount in clean conditions. Apply mounting force only to the ring with the interference fit and never through the rollers. Fill the correct grease quantity and set relubrication intervals from duty cycle and temperature. In service, monitor vibration and temperature trends; rising levels usually indicate lubrication breakdown, contamination or the onset of wear. During gearbox overhauls, inspect rollers and raceways for pitting and smearing before deciding whether to reuse or replace.

7. RAYSDE supply and OEM

RAYSDE is a supplier and OEM partner. We source from partner plants certified to ISO 9001:2015 and support non-standard sizes and OEM supply programmes. Our NNF range serves wind turbine gearbox remanufacturing and repair customers in Europe, and industrial and planetary reducer builders. Send the model, size, quantity and application, and we will confirm availability and a formal quotation. Price on request.

8. FAQ

What does NNF mean in a bearing designation?

NNF denotes a double row, full complement cylindrical roller bearing: two rows of rollers with no cage, giving maximum radial load capacity for the given envelope.

Can NNF bearings run at high speed?

A full complement design has a lower permissible speed than a caged design because adjacent rollers contact each other. Confirm the limiting speed for the specific size, load and lubrication.

Are NNF bearings available with seals?

Many NNF sizes are offered with contact seals and with lubrication grooves and holes in the outer ring. Availability depends on the model, so confirm before ordering.

Does RAYSDE supply NNF bearings for OEM projects?

Yes. RAYSDE acts as a supplier and OEM partner, sourcing from ISO 9001:2015 certified partner plants and supporting non-standard sizes and OEM supply. Price on request.