How to Select the Correct Plasma Cutter
Jeff Noland of HTP
The most important consideration when selecting a plasma cutter is the thickness of the material you will need to cut. Don't just say 1/2-inch because it is a nice round number that comes to mind-get a ruler, caliper, micrometer, or some measuring device and actually measure the thickness of the material you will be working with.

An analogy I like to make is it's like buying horsepower-the more amperage you have, the thicker you will be able to cut. However, more is not always better! A higher amperage machine will have a larger plasma cutting torch to dissipate the higher heat involved with cutting thicker material. The bigger torch is bulkier and won't get into tight places.

Another consideration is cost-a higher amperage machine will cost more money. A 25- to 30-amp machine gives you the ability to cut thin sheetmetal all the way up to 1/4-inch steel. And how much cutting are you really doing beyond that? This should tackle pretty much any automotive project you would be doing in your garage.

If you move up to a 40-amp machine, it will give you the ability to cut 1/2-inch steel. A benefit of a 40-amp machine over a 30-amp machine is it will cut any given thickness faster. So if you were doing a lot of cutting in the 1/4-inch range you would be able to cut at 25 inch/min vs. 12 inch/min.

A 60-amp machine is probably at the top end of the spectrum for anyone doing automotive work. These machines give you the capability to cut 3/4- to 1-inch steel. You better be building a lot frames in your garage to cost justify one of these cutters.

Two more things to take into consideration are air consumption and power supply. Some plasma cutters will operate on 110 volts, some operate on 110 and 220 volts, and some are 220 volts only. Make sure you have the correct voltage and amperage to run the machine you intend to purchase. Don't buy a cutter and then have to spend hundreds of dollars to upgrade your electrical service.

Generally speaking, for those working in their garage, air consumption usually is not an issue. The reason I say that, is because more than likely, you won't be doing "production" cutting at home. Let's say you have a 25-amp machine and are cutting a bracket out of 1/4-inch steel and need to make a 4-inch cut. At 12-inch/min that is a 15-second cut. A 25-amp machine will need about 31/2 cfm at 60 to 80 psi. Even if you have a small air compressor, you probably have enough air in your tank to get the job done. And with cutting speeds in sheetmetal upwards of 100-inch/min, you can cut a lot of sheetmetal before your air compressor will kick in.