An automatic loading unit (3) for bending pin supporting bars (7), which serves an automatic machine for bending electro-welded metal grids, and/or an automatic system for forming three-dimensional lattice-like frames derived from electro- welded steel grids. The automatic loading unit is provided with a magazine (9), which is horizontal or of another type, with a plurality of side-by-side stations which accommodate various bending pin supporting bars (7) having different geometric characteristics. The loading unit is arranged coaxially with the working axis of the bending machine. It can move automatically, arranging one bar at a time proximate to said machine and the upper carriage (6) provided with an adapted grip clamp so as to move it longitudinally and inserting it in the bending machine. The reverse operation likewise occurs automatically. Replacement or loading of the bar (7) on the bending machine occurs fully automatically without the direct manual intervention of the operators thereon.
