Needle roller bearings use rollers whose length is several times their diameter. That proportion gives high radial capacity in a very small radial section, which is why they dominate transmissions, planetary gear sets and hydraulic pumps.
Drawn Cup And Machined Ring
Drawn cup needle bearings use a thin pressed steel outer shell and rely on the housing bore for support and for their final geometry. They are compact and inexpensive but demand a correctly sized and well supported housing.
Machined ring types have a turned and ground outer ring, hold their own geometry, and can be used in lighter housings or where the bore tolerance cannot be held tightly.
With And Without Inner Ring
Where the shaft can be hardened and ground, the needles can run directly on the shaft, saving radial space. That shaft surface then has to meet bearing raceway standards for hardness, roughness and roundness. Where it cannot, an inner ring is used and the shaft only needs a normal machined finish.
Thrust Needle And Combined Types
Thrust needle roller assemblies take axial load in a very small axial height and are used in gearbox stacks and automotive transmissions. Combined bearings take radial and axial load in one component, which reduces part count in compact assemblies.
Cam Followers And Track Rollers
Stud type cam followers and yoke type track rollers are needle bearings with a thick outer ring designed to run directly on a track. They appear in cam drives, conveyors and telescopic sections, and they fail from track surface damage as often as from bearing wear.
