Full complement needle roller bearings from Nadella

These cageless full complement needle roller bearings from the Nadella Group have been used successfully for decades in industrial plants that are exposed to high loads, shocks and vibrations.

Nadella's full complement needle roller bearings have a robust machined and hardened steel outer ring that enables the bearing to support high static and dynamic loads as well as overloads, shock and vibration. 

These bearings are primarily intended for equipment with oscillating movements, but can also be used successfully in high speed applications when properly aligned on the shaft. This alignment is easily achieved by using inner rings with a convex raceway profile (inner rings with the suffix R6 in the designation).

 The needle rollers are held firmly in the outer ring by special end rings or end flanges in the outer ring so that the bearing can be easily brought into the seating position. The difference between Series 3000 Needle Roller Bearings and other needle roller bearings is shown below. 

The reference standard to which Nadella's full complement needle roller bearings are manufactured is ISO 1206.

Standard NA Series Full Complement Needle Roller Bearings with Inner Rings

Full complement needle roller bearings are available with or without a drilled inner ring for shaft diameters from 12 mm. The full complement needle roller bearing type NA has an inner ring with a convex raceway profile as standard. If a wide inner ring or lubrication hole ring is required, these must be ordered separately, as for the corresponding RNA series without inner rings.

In the event of misalignment or angular misalignment, the convex raceway surface of the inner ring can be machined directly in the seating position on the shaft journal by grinding with a diamond grinding wheel with a concave profile. The convex raceway profile of the inner ring is designed to compensate for misalignments and offsets of 1/1000 and does not affect the load carrying capacity of the bearing. The larger radius of the convex profile is necessary to compensate for larger misalignments, but in this case the effective load carrying capacity of the bearing is reduced.

 NA needle roller bearings are manufactured by the Nadella Group in a wide range of series 1000, 2000, 22000 and 3000 for shaft diameters from 12 to 200 mm and can support static loads from 16.5 to 830 kN and dynamic loads from 11 to 257 kN. The bearings are suitable for speeds from 1700 to 22000 rpm with oil lubrication and 1100 to 14000 rpm with grease lubrication.

Full complement standard RNA series needle roller bearings without inner ring

Needle roller bearings of this type have an outer ring with a full complement of rollers similar in design to the outer ring of needle roller bearings of type NA. 

The shaft journal, which is used directly as a raceway instead of the bearing inner ring, must have the correct hardness and surface finish. A Rockwell hardness of 58-64 HRC is sufficient to ensure the maximum permissible load carrying capacity of the bearing. Lower hardness values result in lower static and dynamic load carrying capacity. 

Needle roller bearings type RNA are manufactured by the Nadella Group in a wide range of series 1000, 2000, 22000 and 3000 for shaft diameters from 7.3 to 355 mm, which can support static loads from 4.45 to 1690 kN and dynamic loads from 3.95 to 460 kN. The bearings are suitable for speeds from 1100 to 52000 rpm with oil lubrication and from 720 to 34000 rpm with grease lubrication. 

Bearing Inner Rings

The inner rings of full complement needle roller bearings are made from high quality roller bearing steel which is heat treated and hardened so that the shaft journal in the bearing seat does not need to be heat treated and ground and the bearings can be operated at the full rated load. 

R6 inner rings with crowned raceways 

These inner rings without a lubrication hole have the same width as the outer ring and are available in NA 1000, 2000, 22000 and 3000 series bearings. They can compensate for misalignments of 1/1000 in continuous operation and up to 2/1000 for short periods in the event of sudden deviations due to load changes or overloads. The inner and outer rings can be axially misaligned by up to 5% of the ring width. The designation of a single inner ring for a needle roller bearing consists of the prefix BI, the series and dimension and the suffix R6, e.g. BI 2020 R6. Complete needle roller bearing units with inner rings BI...R6 have a unit designation with the prefix NA, e.g. NA 2035. 

Inner rings with cylindrical raceway

Cylindrical inner rings are available with the same bore dimensions as convex inner rings and in the following versions 

• with a lubrication hole, which allows oil lubrication of the bearing through holes and channels in the shaft (type BIC) 
• with a wide inner ring (type BICG), which allows movement of the inner ring relative to the outer ring (e.g. during thermal expansion of the shaft) or lateral movement of the shaft

In the latter case, which can occur with or without rotation of the shaft, Nadella Group technical personnel should be consulted. 

The use of cylindrical inner rings with standard bearings of the RNA 1000, 2000, 22000 and 3000 series requires the correct alignment of the housing seat and the shaft with respect to the permissible loads. If the use of cylindrical inner rings is not required, it is always better to use needle roller bearings type NA with an inner ring with a convex raceway profile of type "R6" without a lubrication hole and with the same width as the outer ring. In some cases where the bearing is lubricated through channels in the shaft, the inner ring can be replaced by a ring with a lubrication hole on the end face.

Bearing ring tolerances

The inner and outer rings of standard full complement needle roller bearings are manufactured to ISO 492 tolerance classes (Class 0 to DIN 620). For special high precision applications, tighter tolerances may be required, corresponding to tolerance classes 6, 5 and 4 (designations P6, P5, P4).

Radial clearance 

Bearings without inner rings 

The radial clearance in bearings without inner rings is the difference between the nominal diameter under the needle rollers and the shaft diameter. The standard nominal diameters under the needle rollers of RNA bearings for shafts with recommended tolerances always provide the correct radial internal clearance for most applications under normal operating conditions. 

For special applications (high running accuracy, tight fit, etc.), the Nadella Group offers bearings with needle roller sizes that can be selected as follows:

• from the lower half of the standard tolerance class (designation RNA ...TB) 
• from the upper half of the standard tolerance class (designation RNA ... TC)

Bearings without an inner ring of tolerance class TB are mounted on shafts with tolerance k5 and have a reduced radial internal clearance suitable for certain applications. 

The nominal diameter under the needle rollers can be further reduced to increase the running accuracy of the bearing. If a larger radial clearance than normal is required, the shaft diameter should be as close as possible to the nominal dimension, which is normally given by shaft tolerances h5 or g5.

Standard bearing sets with inner rings 

Type NA bearing sets are supplied with a radial clearance suitable for most applications. On request, these bearings can also be supplied with with: 

• a radial clearance in the lower half of the normal tolerance class (NA....TB) 
• a radial internal clearance in the upper half of the normal tolerance class (NA....TC) 

For bore diameters greater than 130 mm, needle roller bearings NA ... TB or NA ... TC are only available on special order.

General bearing installation requirements 

In most cases, the installation of standard needle bearings, with or without inner ring, requires that the shaft seat or mating surface is machined to IT5 or IT6 quality. The bearing housing bore must be machined to IT6 or IT7 quality. Further quality requirements for the shaft and bearing housing can be found in the catalogue. 

The Nadella Group is recognised as the world's leading manufacturer of needle roller bearings. Needle roller bearings are one of the most important components of machines and mechanisms and are used wherever high load carrying capacity, high running accuracy and small dimensions are required. 

Today, the Nadella Group offers one of the widest ranges of needle bearings in the industry. The strength of the product range lies in the ability to produce high quality standard and special products at attractive prices.

The company's many years of experience in product development, design, manufacture and application are incorporated into every bearing.

CMT GmbH is a long-standing premium partner of the Nadella Group. 

CMT GmbH stocks a wide range of products from the Nadella Group. When you contact us, you can rely on the best prices, the shortest delivery times and advice from our specialists, who are always available to help you select Nadella needle bearings.