arranged in this surface which extend parallel with the axis of rotation these longitudinal grooves are designed semicircularly for example and arched toward the axis of rotation thus the surface is so designed that a low friction coefficient is present in an axial direction while in a direction tangential to the rotary movement a high friction coefficient exists the radius of these longitudinal grooves 4 may be 8 microns for example in the additional embodiment in fig3 and 4 a disk 5 39 is used as friction member with corresponding grooves 4 39 applied externally at the rounded disk body here too these grooves 4 39 may be semicircular in design and terminate into each other whereby for example a radius of about 8 microns may be provided in this case the grooves 4 39 are arched externally that is away from the axis of rotation in both cases fig1 to 4 the circular arches of the grooves 4 39 may be rounded at their points of intersection that is they may altogether have a sine form in the embodiment according to fig1 to 4 the friction member is made of hard materials for example agate glass ceramic spinell saphire oxide ceramic carbides or surface coated materials like steel with aluminum oxide coating for example in order to utilize the advantages of an elastic polyurethane or of elastic rubber and plastic masses it is possible according to another embodiment.