It has long been known to use different forms of discs in agricultural implements and often these discs work at an angle in order to till the soil in the desired way. The bearings have often been a weak point, since they are heavily loaded, and in addition they are difficult to build sufficiently impregnable. It is often difficult to manufacture a bearing with sufficient strength and impregnability that is still sufficiently compact. Often the construction height of the bearing viewed in the direction of its central axis has become too great. It has also been shown to be practically difficult to achieve a disc with hub or boss with small axial construction height. The axial extension is therefore often a problem. It is natural for it to be easier to make a sufficiently strong and impregnable bearing if it is allowed to increase in length or height. Furthermore, the discs are subjected to heavy wear and they are therefore commonly made from high-class steel that is hardened and tempered to the best relationship between toughness and hardness. The discs are replaced by the farmer when necessary. Such replacement often takes place in primitive conditions. In continuous production large amounts of discs are assembled and it is desirable for such assembly to be automated. Since the discs are commonly connected against a flat side on the bearing there is no natural orientation of the disc, which can complicate assembly in the field and industrially. Examples of known interfaces are shown in U.S. Pat. No. 2,746,371 and WO02/19791.