12 The particular MIG welder we were using was a Millermatic 175. It will weld up to 1/4-inch-thick pieces of steel—perfect for most car projects—and is super easy to use. On the inside door of the welder is a chart that gives you the corresponding wire speed and voltage settings for a given thickness of steel. Lincoln Electric offers similar units that work the same way. You can also get some cool accessories for small welders like this one, such as a spool gun for welding aluminum.