More explain about equipments ... Welding processes -as they apply to the home Scooter builder...
Okay, great, so what does all this mean to a guy that has a home shop and needs to buy a welding machine?
Well, by knowing something about the different processes, you can better decide which one best suits the application.
GTAW (TIG) is certainly the nicest process there is.
The tight, controlled arc, and purity of the welds makes it ideal in situations where high strength and weld bead appearance are critical.
For chromoly, stainless steel, and aluminum there is nothing better.
TIG works wonders on really thin sheet metal. A highly skilled welder can literally weld razor blades together!
There is a price, however. A professional quality GTAW machine is required to weld anything over 1/8" thick, and this gets expensive. The "entry level" professional quality machines from manufactures like Lincoln, Miller, and Hobart will cost you about $1600. That's a bargain considering what these machines (especially the Lincoln) can do, but that is still expensive enough to make it sting quite a bit.

The other problem is that TIG welding requires a high degree of skill. It is easily the hardest process for the beginner to learn to do well, and the amount of time required to become truly proficient is considerable. Not a big deal for a professional welder, but more than enough to challenge the average home builder.
SMAW (STICK) is the oldest arc welding process, and is still in frequent use. There are situations where STICK is simply the most convenient process. In outdoor envirmoments where gas shielding is not feasible, a flux shielded electrode does the trick. There are a large variety of general purpose and specialty electrodes available, giving the welder the ability to match the filler alloy to the application. In my opinion, STICK is the best welding process to learn first. Learning how to control arc length, manipulation, and travel speed gives one better technique in other processes.
STICK machines are simple, rugged, and offer more "power per dollar spent" than any other machine. For someone on a budget, $300 to $500 will buy a machine that will do just about anything on mild steel or stainless.
The level of skill required to master STICK is moderate, so if you are new to welding and start out learning it first, plan on going through a few pounds of electrodes learning how to run a good bead in different positions.
GMAW (MIG) is the most user-friendly welding process of all. A good MIG machine is all the home builder needs to weld just about anything. High quality 220V machines from manufacturers like Lincoln, Miller, Hobart, and ESAB will absolutely spoil you rotten!
Easy to learn for the beginner.
Versatile and fast, with excellent weld bead appearance.
Using solid wire and shielding gas will make very clean welds with little spatter, and good penetration.
Flux core wire can provide slightly deeper penetration, and can be used in outdoor enviroments where gas shielding is not feasible.
OXY/FUEL welding is definitely a lost art. In the hands of an expert welder, this process can make high quality welds.
The preheating of the base metal caused by the neutral flame allows the weld to cool more slowly, making it tougher.
Mild steel, stainless, chromoly, and aluminum are no problem.
Inital investment can range from low to moderate, depending on the quality of the torch kit. A cheap OXY/FUEL kit can cost as little as $100 on sale at Harbor Freight. A professional quality kit can easily cost as much as $600 at a welding store.