As I posted earlier in this thread I recommend 120 psi with a 3/8" hose to the plasma cutter. This is because you need the pressure and volume to set and run your plasma cutter efficiently.
How to set your air pressure on your plasma cutter can differ from one to another, but this is the basic why to set it.
Most but not all plasma cutters have an adjustable regulator and gauge. Turn your plasma cutter on, if it has a set switch or set setting this will let the air start to flow from the torch. On some plasma cutters you have to bump the trigger to get it to post flow. With the air flowing set your regulator to the recommend pressure in the manual if it has a setting listed ( most manuals give you a range from say 60 to 80 psi) so set it at about 75psi this setting will give the 20,000fps coming out of you tip/nozzle to ionize the air( so it will ignite ). Set the switch back to the cut position, look at the gauge it can read from 80 to 95 psi or more. Note: MORE AIR PRESSURE then listed in the manual will not make it cut better...
This is because the pressure in the hose has increased. This is why you will get a quick burst of air when you pull the trigger till the pressure equalizes and will stay study at the 75psi setting you need for cutting.
Why the 75psi, well I have found out that most plasma cutters in the 40 to 60 amp range work best at this setting for cutting mild steel up to 1/2".
Most but not all plasma cutter company's/retailers work on the K.I.S.S. (keep it simple stupid) system. Case in point the 62204 plasma cutter sold by Harbor Freight. This is a good plasma cutter and will do a lot of great cutting, but HF only sells one size tip/nozzle (0.9mm, 40 amp) for that plasma cutter to do all your cutting. And yes that works if your a scrapper or just cut metal then grind to size and don't care about extra doss, clean up time, clean straight cuts, sharp corners, etc. this system works. So the 62204 has a IPT40 torch on it you can get tips/nozzles in 20, 30 and 40 amps, as well as 40 amp drag and shielded consumables. So why don't HF sell them? Well most buyers wouldn't now what all those consumables were for and you know that the sales person would never even have a clue what they were for, so the K.I.S.S. system works here.
So now your in the garage and you want to cut out some flowers for some yard art that your wife would like from 1/16" sheet, you fire up the plasma cutter, (maybe even) install a new tip/nozzle and start cutting, yea, the flowers look like (zombie snow flakes) not flowers. So you try different air pressures and amp setting, things still ain't getting any better, so now you start thinking this piece of junk plasma cutter. Well its not the plasma cutter the K.I.S.S. system is not going to cut it in this case. (pun intended)