Flanges may be turned (1) by beating down the plate edge with hand mauls, while the plate is suitably held on a former or between two heavy bars, or (2) by the hydraulic flanging machine. Plates are usually heated to a bright red along the edge to be flanged. Several heats may be necessary to flange the edge of a large plate, as only 3 or 4 feet can be heated along the edge at one time and flanged before undue cooling.

Flanged plates must always be annealed after flanging is completed as the flanging heats are local and they set up internal stresses in the metal. Large plates partly or wholly flanged may crack if left to cool over night unannealed, hence it is well to keep plates hot, or at least warm, until final annealing can be done.