An inner spring assembly embodying a generally channel-shaped border wire of the type which is provided with a continuous groove with straight sides and into which the end convolutions of the helical bedsprings of the assembly project in tangential fashion and about which the border wire is crimped to form a loose self-aligning non-rigid interconnection between springs and border wire. The border wire is formed from solid rod-like wire stock by a cold rolling operation in a shaping mill thereby obviating the necessity of resorting to machining and heat treating and eliminating waste material that is a consequence of machining. The rolling operation includes a reshaping of the solid cylindrical stock to a grooved border wire that offers a greater bending strength than like diameter solid border wire of the like weight per unit length.