NTN HK2820 LL/3AS Nadelhülsen (28x35x20)

As a needle roller bearing, this bearing carries high radial loads in a very compact section. The principal dimensions are 28x35x20 mm at a weight of 0.04 kg; the further technical details are listed in the specification table. This variant features a contact seal. A sealed drawn cup needle roller bearing: the smallest radial section height, but with its own closure of the rolling chamber.

This version of the drawn cup needle roller bearing carries a contact seal at both end faces. The benefit is grounded in the construction itself: a thin-walled, drawn cup offers no space for an elaborate enclosure by the surrounding structure, and at many mounting locations — rocker arms, joints, adjusting mechanisms, open gear attachments — a tight chamber around the bearing position cannot be realised in any case.

The integrated seal keeps the grease charge with the needle set and excludes dust, chips and moisture, whose hard fractions leave indentations in the line contact of the needles and continue to act as local peaks in contact pressure. The counterpart is a frictional torque at the rubbing lip: it generates heat, lowers the permissible speed relative to the version without a sealing element, and the seal material limits the operating temperature and the media resistance.

Whether relubrication is provided for at all depends on the specific version. The sealing changes nothing about the mounting conditions: after pressing in, the cup takes on the form of the housing bore, which is why that bore has to be closely toleranced, accurate in form and load-bearing; without a separate inner ring the shaft surface forms the raceway and has to be hardened and ground accordingly; the design takes no axial force, and misalignment between shaft and bore is permissible only to a small extent.