This is a moderately priced MIG welder, a Millermatic 175 that will do nearly everything a typical custom car builder needs. Having both the machine and bottle of shielding gas on a cart makes the whole outfit easy to move around your garage or shop.
Here is the "business end" of the MIG welder-the gun that feeds the welding wire and floods the weld area with a shielding gas that keeps the metal in the weld zone from oxidizing.
Most MIG welders can use a variety of wire sizes. You change the wire size by replacing the feed spool inside the machine.
Here's a welded joint on square steel tubing with a 1/8-inch wall thickness. This is a common thickness for aftermarket chassis components.
Here's a welded joint on 19-gauge sheetmetal-typical of what you'd use for custom body repair or modification. Note the low-profile weld bead, and the small amount of distortion on the panel.
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MIG Welding Fundamentals - Pull The Trigger- CRM Tech-Do Try This At Home
MIG Welding Fundamentals For Custom Car Hobbyists
By Ron Covell
Custom Rodder Magazine, May 2006
Every automotive project will require at least a little bit of welding along the way, and there is no question that MIG welding is the most commonly used process for both body and chassis work on customs and rods. MIG welding is fast, strong, relatively easy to learn, and causes less distortion than most other welding processes. The machines are pretty affordable too, usually costing hundreds of dollars less than TIG welders. (We'll look at TIG welders in a future article.)
Most MIG welding machines have a self-contained power unit that holds a spool of filler wire. There is a cable that goes from the power unit to the welding gun, and the welding current and the filler wire pass through this cable. Many builders use a cart to hold the welder and the bottle of shielding gas together, making the whole outfit easy to move. Setup is easy-you turn on the gas, set the power and wire feed controls on the welder, place the ground clamp on the work piece, and you're ready to weld.
As with any welding process, it takes a little practice to get proficient with MIG welding, but most people are able to learn the basics fairly quickly. Before you start welding, there are a few things to learn about wire selection, machine setup, and gun position and movement.
There are many filler wire diameters available for MIG welding. In general, the thicker the base metal you are using, the larger the wire size. For sheetmetal, .024-inch wire is a good place to start. If you are welding mostly stock that is 1/8-inch or thicker, you might want to use .030- or .035-inch wire. ER 70 S-6 welding wire is probably the most commonly used, and should be good for most custom and rod applications.
Each MIG machine will have suggested settings for wire feed and welding current, usually these can be changed by turning a dial. Most welders come with a chart or booklet that will recommend starting points for these settings, but you should always do some experimentation to find what works best for your particular application. There are also online sources for this information, such as www.millerwelds.com
The shielding gas usually used for MIG welding steel is a mixture of 75-percent argon and 25-percent CO2. There are flux-cored wires that do not require any shielding gas, but they are not well suited to the type of work done on our favorite cars.
Once the machine is fitted with the proper wire and the settings are dialed in, the next thing to look at is the direction of movement of the gun. You can angle the gun toward the puddle and drag it away, so the puddle is trailing the gun, (this is called the drag technique), or you can push the puddle with the gun, so that the gun is leading the puddle. Generally, dragging the weld gives deeper penetration with more weld bead buildup, while pushing the weld gives shallower penetration with a broader, lower-profile bead. You should experiment with both of these techniques to find your own preference, but many people use the drag technique for plate, and the push technique for sheetmetal.
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