I had to make 36 1.5-in.-thick, 3.5-in.-square blocks of 1018 steel into U-shaped pieces for mounting to a die in a stamping press. The slot of the U-shape ran 2-in. long, 1.250-in. wide and completely through the material thickness. While I would have liked to use a 1-in.-diameter, 1.5-in.-long shell mill to do the whole slot, the equipment on hand would not support the method. What worked was to machine a hole at the bottom of the U shape using 1.250-in.-diameter annular cutter, then I used a bandsaw to cut the sidewalls. Lastly, I finished cut to size.