When choosing a plasma cutter, there are a few things to consider. Plasma cutters are rated for different material thicknesses.
The rated cut is the thickness you should get a clean precise cut at a certain speed (normally around 12 – 15 inches per minute) on mild steel. Cutting stainless steel, aluminum and other metals will have a different, normally lesser, rated cut thickness. The plasma cutter will also have a maximum sever thickness. The sever thickness is the maximum thickness the plasma cutter can cut through; although in most cases there will be with some amount of slag build up on the bottom of the cut. The bigger or more amperage the plasma cutter, the thicker metal it can cut.
The Miller line of plasma cutters include:
- 1\8-inch (Spectrum 125C 12 amps)
- 3\8-inch (Spectrum 375 27 amps and 375X-TREME 30 amps)
- 5\8-inch (Spectrum 625X-TREME 40 amps)
- 7\8-inch (Spectrum 875 and 875 Autoline both 60 amps)
Always pick a plasma cutter that will cut a little bit thicker than what you think your maximum cut thickness would be. When choosing a plasma cutter for the first time, customer feedback has shown that they would have gone a size larger after they have made their purchase. Don’t be afraid to ask your distributor or contact the factory and ask for a recommendation.
Plasma Cutter Input Power
Once you’ve decided on what the maximum material thickness you’ll need, the next step is to look at its primary input power. Miller makes four plasma cutters that run off of 115 volts AC. The Spectrum 125C, and Spectrum 375X-TREME, and the Spectrum 625X-TREME will run off a 115 volt 20 amp breaker.
The Spectrum 375, Spectrum 375X-TREME, and Spectrum 625X-TREME will also run off of single phase 200/220 volts AC. These three machines will have reduced cutting capacity when running off of 110 volts. The Spectrum 875 runs off of single phase 200/220 volts AC, while the Spectrum 875 Autoline will run off of single or three phase power at voltages ranging from 200 to 600 volts AC.
Plasma Cutter Air Supply
The final factor to consider when purchasing a plasma cutter is the air supply and amount of air needed to run the different models. While it is convenient to purchase a model like the Spectrum 125C which has a built in compressor, there are some additional things to keep in mind.
Plasma cutters with built in compressors normally have cooling coils in place of filters to remove the moisture from the air supply. This type of system —when used in a highly humid environment — can cause excess moisture to enter the torch and can cause reduced consumable life, arc outages and less than ideal cuts. It is important to make sure your compressor can meet the needed air requirements for the plasma cutter you’re choosing.
The following are the air requirements for the rest of Millers Plasma cutters.
- Spectrum 375 and 375X-TREME: 5cfm@ 90-120psi
- Spectrum 625X-TREME: 6cfm@ 90-120psi
- Spectrum 875 and 875: Autoline 6.75cfm@ 90-120psi
Taking these few things into consideration before you purchase a plasma cutter will make sure you are content with your purchase. Visit for more details on the Miller line of plasma cutters.
