It has been over 60 years since Dr Georg Schaeffler and his brother, Dr Wilhelm Schaeffler, invented the first Caged Needle Roller Bearing, a design which quickly became indispensable in many industries and remains so today. Now, Needle Roller Bearings (NRBs) are found in a variety of applications, including; gearboxes, automotive power transmission systems, hydraulic pumps, heavy machinery, planetary gear sets, and the list goes on.
The caged design, created by the Schaeffler brothers back in 1949, provided a solution to the issues that the full complement type (containing extra rollers and with no retainer/cage) experienced. In particular, Rolling element bearings of the time tended to skew, leading to increased frictional resistance and heat, especially at high running speeds. Introducing the cage meant the needles could be axially guided, therefore removing the chance of skewing and allowing for high speeds and low friction.
The full complement type still exists today as an option within each range of NRBs. When choosing the NRB for an application you can choose between the caged type or full complement type. The main difference in performance between the two types is that the full complement type can handle heavier loads, but at far lower speeds. For example, if we compare the two IKO bearings in the table below, we can see that the TR203320, while still taking a fair amount of load, runs at much higher rotational speeds than the GTR203320.
| Part Number | Type | Dimensions (mm) | Dynamic Load Rating (N) | Static Load Rating (N) | Allowable Rotational Speed (min-1) |
|---|---|---|---|---|---|
| TR203320 IKO | Caged | 20X33X20 | 24,300 | 26,500 | 20,000 |
| GTR203320 IKO | Full Complement | 20X33X20 | 29,200 | 37,200 | 7,500 |
As the smallest and lightest members of the roller bearing family, NRBs offer specific advantages where load, speed, and space availability are factors of concern. Compared to the other roller bearing types - for example, Cylindrical Roller Bearings - NRBs have a very compact design and low sectional height. Despite this, they still maintain a high load-carrying capacity, and this is particularly true for Machined Needle Roller Bearings (MNRBs).
Machined Needle Roller Bearings have a larger sectional height than the lighter weight, less heavy duty Drawn Cup/Shell Type NRBs and can therefore handle almost double the amount of load while performing at the same high speeds. They also perform just as well running at lower speeds. Even so, the MNRB still has a much smaller sectional height than all the other roller bearing types and can match many of them in terms of load-carrying capacity.
They differ from some roller bearings though because they can’t accommodate axial load. However, this makes them particularly suitable for use as non-locating bearings. Non-locating bearings are essential for many industrial applications as they adjust for the thermal expansion of the shaft during operation while sitting opposite the locating bearing, extending the service life of both the locating bearing and the machine itself. It’s important to note that this is the case where the bearing has an inner ring. When the bearing doesn’t have an inner ring, the facility to accommodate axial displacement is dependent on the shaft raceway width.
Needle Roller Bearings with a Separable Cage are very similar to the MNRB, except these bearings have a separable outer ring as well as the separable inner ring the MNRB has. Therefore, the cage is entirely separable from the inner and outer rings. This simple structure, used with a Needle Roller Cage, results in extremely high accuracy, as the radial clearance is dictated in the selection and combination of the component parts. Additionally, higher speeds are reached thanks to the reduced friction afforded by the lack of ‘ribs’ or ‘collars’ on the outer ring, unlike in the MNRB.
As mentioned above, the uses and applications for NRBs are vast and varied and present in many different industries. Possibly the largest user of NRBs is the automotive industry, especially considering that an average vehicle drive shaft normally contains at least 8 NRBs, or even more if it’s long and operates on steep inclines. Similarly, other applications with drives shafts (or not stationary/rigid shafts) also use NRBs, such as in printing, 3D printing, laser cutting, and CNC machines.
We have recently launched a whole range of Machined Needle Roller Bearings and Needle Roller Bearings with a Separable Cage in both IKO and INA brands. Both of these manufacturers are top in our industry and produce high quality, reliable parts.
Check out the ranges here or get in touch withour Sales Team to find out more.