SKF NATR25 PPX Stützrollen (25x52x25)

As a track or cam roller, this component runs directly on a mating track or cam surface. The principal dimensions are 25x52x25 mm at a weight of 0.275 kg; the further technical details are listed in the specification table. The contact seal on both sides keeps the lubricant in the rolling chamber and the debris from the track out of it — on this design the usual reason for the selection.

The support roller differs from an ordinary rolling bearing at one decisive point: its outer ring is not mounted in a housing but runs directly on a rail, a track or a cam disc. It is therefore executed with a thick wall and hardened through the running depth under load, since it carries the contact pressure from the line or point contact with the mating track in addition to the load coming from the rolling set inside.

From this follows a rule that is frequently overlooked with this design: the mating track is part of 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; 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 distributes the load over the full width as long as roller and track are aligned to one another, whereas a crowned running surface takes up an angular error without forcing the pressure out to the edge. Inside, the rolling set guides the roller on its pin; the roller is set onto a journal through its bore and supported on both sides, so that the force path remains symmetrical.

The contact seal on both sides closes the rolling chamber off from the surroundings and keeps out the debris that inevitably arises at a running track; in return its frictional torque and the seal material limit speed and operating temperature. Rings and rolling elements are made of standard bearing steel.