In a method of and machine for forming a nonwoven bias yarn assembly comprising two superposed nonwoven bias yarn sub-assemblies, each yarn is transferred by a yarn transfer member from an opening in a yarn guide member to another opening in the yarn guide member in such a way that each yarn is caused, in a succession of forward transfer steps, to follow the yarn preceding it from one opeining to another along a non-intersecting path until the yarn at a first end opening in the path arrives at a second end opening in the path located at the opposite end of the path and the yarn at the second end opening in the path arrives at the first end opening and then, in a succession of return transfer steps, to follow the yarn preceding it from one opening to another along the non-intersecting path in the opposite direction until the yarn from the second end opening in the path arrives at the first end opening and the yarn from the first end opening arrives at the second end opening. The forward and return transfer steps are then successively repeated. IPC D03D.