A wire feeding unit and an associated wire length measuring unit advance supply wire through a cutting zone and at the same time the advanced supply wire is guided by a wire transfer system across transversely spaced endless conveyor chains of a wire propelling conveyor. The feeding unit is automatically stopped when it has advanced a measured length of the supply wire and the transfer system tensions the advanced supply wire while it is held against lengthwise displacement by the stopped feeding unit. The wire transfer system then engages the stopped and tensioned wire length with gripping jaws on the conveyor chains, the gripping jaws are closed, and the supply wire is severed in the cutting zone. Tensioning of the advanced supply wire prevents it from sagging between the transversely spaced conveyor gripping jaws and thereby avoids undesirable length variations of the cut off portion of the supply wire. The mechanism for severing the supply wire in the cutting zone is laterally adjustable to clear the adjacent end of the cut off wire length during subsequent advance movement of the conveyor chains.