The Lathe is a multi-block construction which allows for faster and cheaper construction of rods. The Lathe allows rods at a 2:1 from ingots, making the creation of machine structures much cheaper. Along with the Rolling Machine, it is one of the first machines you want to make, as it will decrease the costs of further machines significantly. Use the Holo-Projector to complete the structure, then right click the Lathe machine block.
Items are inserted via the input hatch and the rods can be retrieved from the output hatch.