SKF NATR17 PP Stützrollen (17x40x21)

As a track or cam roller, this component runs directly on a mating track or cam surface. The principal dimensions are 17x40x21 mm at a weight of 0.139 kg; the further technical details are listed in the specification table. What is recorded for these items is the material — rings and rolling elements in standard bearing steel — but not the design of the seal.

The support roller is characterised by the fact that its outer ring does not sit in a housing but forms the running surface itself: it rolls directly on a rail, a track or a cam disc and is therefore executed with a thick wall and hardened through the running depth under load. From this follows the decisive design rule for this type — the mating track belongs to the bearing arrangement.

Its hardness, its surface finish and its course have a share in determining what force the pairing transmits in the long term, and a track that is too soft or uneven limits the bearing position regardless of the size of the roller. The profile of the running surface likewise belongs in the selection: a cylindrical running surface carries over the full width as long as roller and track are aligned, a crowned one takes up an angular error without forcing the pressure out to the edge.

The roller is set onto a journal through its bore and supported on both sides; rings and rolling elements are made of standard bearing steel. No separate catalogue attribute for the sealing of these items is available. That matters for the selection, because the design of the seal simultaneously governs two quantities that stand against one another in this type: the protection against the debris that arises at every running track, and the frictional torque, which can make a roller that is not driven but carried along by its track slide if it comes out too high.

The information is to be taken from the type designation and the specification table of the individual item and reconciled with the conditions at the mounting location.