SKF 1204 ETN9/C3 Pendelkugellager (20x47x14)

As a self-aligning ball bearing, this bearing compensates for misalignment and shaft deflection. The dynamic load rating of 12.7 kN characterises this bearing. The static load rating is 3.4 kN. The limiting speed is 20000 rpm. This variant features increased radial clearance (C3). What counts at this bearing position is not the clearance as delivered but the play that remains after drive-up and in warm service.

Increased clearance (C3) has a very concrete reason in this design. Self-aligning ball bearings are frequently supplied with a tapered bore and set onto a plain, unstepped shaft by way of an adapter sleeve — the method with which long shafts are built up in plummer block housings. During drive-up the inner ring is deliberately expanded, and the mounting is controlled by the clearance remaining in the process; without a sufficiently large initial play, too little of it would be left after drive-up.

On a cylindrical seat the same relationship acts on a smaller scale through the inner ring fit, and in service the temperature difference between the warmer inner and the cooler outer ring is added to it. If too little play remains at the end, the ball set is braced against the raceways; frictional torque and temperature rise, and the additional heat reduces the play further.

The larger clearance class changes nothing about the properties of the design: the inner ring unit remains able to swivel in the outer ring, the bearing position compensates for misalignment and shaft deflection, the load rating stays tied to the low conformity of the spherical outer raceway, and axial forces are permissible only to a modest extent.

Rings and balls are made of through-hardened standard bearing steel. The open form presupposes sealing and lubricant supply by the surrounding construction. For the layout, the type of seat, the drive-up distance or fit, and the temperature profile to be expected should be assessed together.