Wire Change In A Mig WelderMIG wire is something you rarely have to think about. You just get used to turning on the machine and blasting away. Here's what to do when the spool runs out or if you want to change to a different type of wire.
 When you pop the hood of your...  When you pop the hood of your welder, it should look something like this. The roller mechanism (A) pulls the wire from the spool (B), pushing it out to the torch nozzle. The tension adjustment knob (C) changes the amount of pressure the rollers apply to the wire. The electrodes (D) are adjustable, too, allowing the operator to switch the polarity of the machine. Most MIG welding is done in straight polarity mode-meaning the electrode (the MIG wire) is positive and the work is ground.
We've got 0.030-inch ER70S-6 steel wire mounted in place now, but what if we want to change to a different type or thickness of wire? First, put a piece of tape across the spool to keep it from unwinding, then cut the wire with a pair of side cutters anywhere between the spool and the rollers. |  Loosen the tension adjustment...  Loosen the tension adjustment knob and tilt it out of the way. Now rotate the hinged roller up and out of the way. |  |
 Notice the pair of grooves...  Notice the pair of grooves in the rollers? One pair of grooves is wider than the other. If you're changing wire diameter, you'll also use a matching roller. The rollers have markings indicating the wire sizes they fit. Ours fit 0.030- and 0.023-inch wire. Install the desired size with the markings facing up. In other words, if we were to install thinner 0.023-inch wire, we'd flip both upper and lower rollers over. |  There are a variety of ways...  There are a variety of ways the wire spool can be retained. Ours was a simple spring-loaded, quick-release collar. Remove it and the spool tension spring, and you can now remove the spool and replace it with a new one. |  Feed the new wire through...  Feed the new wire through the rollers and into the torch cable. You only need to push about an inch of wire in-you can turn the machine on and have it push the wire all the way through for you. Make sure the wire lines up correctly with the grooves in the rollers. Lower the hinged roller and tilt the tension adjustment knob back into place. |
 If you did change wire diameter,...  If you did change wire diameter, know that you also need to change the collet in the torch tip. The collet (center) is also marked for a certain diameter wire. It threads into the torch handle (right), and the copper gas nozzle (left) slips over the whole assembly. |  The last thing to do before...  The last thing to do before beginning to weld is adjust the tension on the wire. Cut the wire as close as possible to the end of the torch tip, place it flush against a flat surface (hopefully an ungrounded, nonmetallic surface), and pull the trigger. The wire feed should push the torch tip away from the surface. If it does not, look to see if the rollers are turning but no wire is being fed. That means there's not enough tension on the wire. Tighten the tension adjustment knob until the rollers stop slipping and start feeding the wire. Conversely, too much tension can be hard on the rollers. Back off the adjustment knob until the rollers start to slip, then tighten the adjustment knob about 1/4 turn. The best tension setting is the point just past where the rollers stop slipping. | |