Hobbies And Interests
Heat Transfer
Plasma cutters shoot a fine jet of super-heated gas or plasma, known as a fourth state of matter. It can cut through steel like it's frosting. Plasma cutters are also capable of cutting a much finer edge than other heat-cutting methods such as an oxyacetylene torch. The issue with cutting enamel-coated steel with a plasma cutter is the enamel is a very good heat conductor. The heat from the plasma cutter can delimitate the enamel because the enamel and the steel will heat and cool at different rates. It can also discolor and deform the enamel.
Discontinue Heat Transference
Cutting a groove in the enamel will stop the transference of heat. To discolor or distort, the enamel must be contiguous, in which case it's a very efficient conductor of heat. If you score, or better yet, groove the enamel, it's interrupted. Heat traveling across its surface doesn't transfer across the small groove, stopping the spread of discoloration or distortion. You can prescore a line with a window cutter. Follow the groove with a scalpel-shaped detail file to make a notch.
Shield From Heat
Shield the enamel from heat and slag. A step as simple as taping adjacent to your cut-mark can reduce discoloration and protect the surface from slag. The tape will burn easily, but it prevents the outer surface from changing temperature as quickly and the hottest slag nearest the cut-mark cools very quickly--fast enough to cool in the time that it takes to burn its way through tape. Other heavier shielding can be used for greater protection.
Cut And Grind
Grinding is the best way to make an extremely clean cut in enameled metal. If you cut enameled metal with a plasma cutter, it's going to affect the enamel to some degree, just as it affects the edge of the steel cut. If you can live with some amount of discoloration and distortion, good. Otherwise, make your plasma cut adjacent to where you want your finished line. After the plasma cut, come back with an abrasive wheel and gently grind the edge to your mark.