Well, I don't guess it is really a 'tool', unless you have a bucket of golfballs you need to get out of your way and never want to see them again, or some extra tomatoes, potatos, or anything else you want to shove down the barrel. This cannon is air powered, so based on NC laws, it is legal, and it does not use anything combustible as a propellant.
Large aluminum tube for chamber (pick your size)
Small aluminum tube for barrel (pick your size, mine is 1.75 .120, golfball fits perfect.
Aluminum circle for back (1/4")
Aluminum circle for front cap (1/8" or thicker)
Aluminum 'fins' to weld to the barrel to hold barrel centered when welding the front cap on (these are not visible when assembled)
Aluminum circle (1/8") with 1/4" hole in center, flexible rubber diaphragm (about 1/8"-3/16" thick works well), the rubber needs to be slightly larger than ID of chamber, aluminum circle needs to be slightly smaller.
PVC that will fit inside chamber, you can take a larger piece and cut a section out to make it smaller for a tight fit.
Ball valve, schrader valve.
Gauge (if you like)
I will go into more detail later on the assembly, I have pressurized it to about 130psi, which seems to be more than plenty, it will launch a golfball out of sight, I put a large dent in a piece of 1/8" aluminum with a frozen tomato.