Plasma Cutting - Selecting the right amperage
A number one question I often get is "What's the thinnest material this metal can cut?" That of course to an experienced user of a plasma cutter is a relative question. In reality, any plasma cutter really has no bottom, or minimum thickness that it can cut. It's sort of like trying to define what the smallest fire a single match can set would be. In other words, every plasma cutter can cut through the thinnest metal sheet you could find. Not all would do it as well, though based off of the tip design and diamerter of the orifice in the tip. Some would leave a broader, wider kerf, others would look like a razor blade made the cut. It would depend upon the amperage used as well. Amperage control is key to giving the best quality cut on any given thickness of metal. But, at a point lowering the amperage, makes no economical or practical sense. Speed and quality have to be balanced. As amps are lowered, quality can go up, but speed can drop drastically. And at a certain point, quality begins to quickly drop when amps are lowered too far. There is a rule of thumb that I have come up with when using a plasma cutter to achieve the best cut. You won’t find it in any plasma cutting manuals though. I have found that 20 amps is truly the lowest practical limit for a plasma cutter. That amperage is good up to 1/8” of an inch. After 1/8” you can typically add 10 amps for every additional 1/8” of cut. While this isn’t perfect for all conditions, it works well as a general guide. For 3/8” cut, 40 amps works out well for most brands of plasma cutters. For ½” cut, 50 amps works out well, etc. Keep in mind this isn’t the maximum thickness of cut that a plasma cutter is capable of cutting but rather, it is a good rule to follow for decent cutting speed and quality. For most torches, various tip sizes are available, each with its optimum cut range.