and second parts 7 8 in the magnitude of 0 01 mm is advantageously made possible and is maintained because play has been eliminated and the supporting screws 33 are therefore fixed as a result a faultless supply of weft threads is guaranteed with little air loss the second part 8 is pivoted via an operating mechanism 3 on housing part 5 for this purpose on the second part 8 is constructed a projection 13 into which a rolling bearing 14 is inserted the rolling bearing 14 is carried on ring bearing 15 and is retained thereon by means of a ring 16 the housing part 5 has a cylindrical projection 17 on its end opposite the flange 6 the ring bearing 15 is disposed in an axially displaceable manner on this projection and is prevented from twisting by a wedge guide 18 this wedge guide 18 is at the same time used to guide operating device 3 with the second part 8 during the axial displacement in the ring bearing 15 are constructed six blind holes 19 which are equally spaced along on a circular line on the free end of the projection 17 is a clamping ring 20 which has a radially inwardly directed projection 21.