WELDING WITH MIG
IDEALLY AN aluminium body would need TIG welding, but MIG is most practical for the inner steelwork and chassis, and perhaps TIG for experienced welders. TIG is the neater, more artisan method, but requires the most skill – a case of melting the pieces to be joined using the torch in one hand, while feeding the filler wire in (at the correct speed and place) with the other. Indeed, to start welding, many suggest learning on TIG, then going to MIG, as you’ll then have an appreciation of the process and may, therefore, have fewer issues. MIG is a simpler and faster process, more suited to the home welder.
Get to know your machine by carefully reading the instructions. They will suggest the best amps and wire speed for the thickness of plate you are working with, and the best wire size. The notes will also explain how to feed the wire through to the welding tip and trim off the wire end using side cutters.
Position the torch close in, wearing a visor and protective clothing, and press the trigger. The wire will arc, but will also feed out automatically, so you need to move the torch as it does so. In the first instance try a simple tack weld with the torch held in one position – it takes only a second or two. When making a longer run of weld, move the torch along the join at a speed that allows the metal to fuse together. Aim for a smooth profiled weld – it’s just a matter of practice to get the speed and distance correct. Too slow, and the weld profile will be shallow: too fast, and the profile will be high and narrow. Everything stops if you release the trigger. You’ll eventually get to learn from the sound during welding when it is going right, with a nice, domed, penetrating weld forming. Let’s look over the shoulder of Kingsley Cars’ welder, Steve Fuller, as he demonstrates some simple practice excercises, and some problems you can expect in getting a handle on the basics of MIG welding. A typical gas MIG welder. The gas bottle is at the rear of the unit. The earth strap (top) is secured to clean metal near the area to be welded.