Abstract: The opening cylinder comprising a cylindrical ring serving as a needle support and being provided with needle-housing bores extending from the inner ring surface to the outer one is designed to carry needles comprising a point section of generally tapered shape and a shaft section, the latter being pressed into and seated with force fit in a radially inner section of a corresponding one of said bores. A radially outer section of the bore surrounds a portion of said needle point section so as to form an annular groove therearound at the orifice of the bore in the outer ring surface. The radially inner section of the bore or at least part thereof has a diameter which is at least as great as the diameter of the outer section of the bore in the range of its orifice in the outer ring surface.