The MIG gun is subject to much abuse, and a little care along the way can help keep it and your welds nice. As the nozzle and contact tube (the thing the wire feeds out of) gets dirty and weld spatter and soot builds up, it is more likely for the wire to stick in the contact tube as well as drop some of that spatter on your work, not to mention the path for the shielding gas is now somewhat obstructed. | 
With the nozzle off, we can see the dirty contact tip and how far up the spatter and soot goes. Contact tips are made for certain wire thicknesses and it's important to keep them matched when buying wire or changing sizes. 0.030-inch wire is a good size for most automotive work under 145 amps, while 0.024-inch would be better for sheetmetal work since it doesn't add as much filler to the weld, leaving less to grind off later. | 
One easy way to keep your gun clean and working properly, not to mention cutting down on the amount of spatter welding produces, is to get a jar or spray can of nozzle dip and apply regularly. As it gets dirty, just wipe it with a rag and re-dip. |
Now that you've had the CLASSIC TRUCKS MIG welding crash course, start welding all your scrap metal together, or go to your local metal yard, buy a bunch of remnant pieces, and have a blast learning to weld while doing so! And don't forget to check out Miller's Web site for lots more products, in-depth info including welding videos, and projects you can do at home. | | |