PURPOSE: To prevent the undesired forward movement of a wire or bar, by selectively relating the timing of operation of a guide pipe to the rotation of a cutter shaft so as to maximally guide the wire or bar without causing it to be miscut.

CONSTITUTION: An inlet guide 5 is provided with a guide pipe (not shown in the drawing) located downstream to a fixed guide and supported to extend in the direction of a passage line P. When a wire or bar passing through the inlet guide 5 is rotated, the guide pipe is moved back to an upstream-end retracted position in which the wire or bar does not come into contact with cutters. When the upper and the lower cutters 3, 4 are displaced away from the passage line P during the rotation of the wire or bar, the guide pipe is moved forth downstream to a downstream-end protruded position to shorten the distance l between the guide pipe and an outlet guide 7 to prevent the undesired forward movement of the wire or bar.