Electrical-mechanical tubing, or EMT, is galvanized steel tubing commonly used as conduit for running electrical wires through a building. EMT is also used in a variety of metal welding projects, due to its availability, size variety and is easily worked into different shapes through bending. Welding EMT is normally accomplished through metal inert gas welding, or MIG. MIG welding produces a protective gas surrounding the weld puddle, keeping atmospheric elements from affecting the weld. Also called wire welding, MIG welders operate by feeding a steel wire that is fed through the machine to the nozzle, forming the welding material.
Things You'll Need
Tinted welding helmet
Long sleeve shirt
Steel MIG welding wire
Set up your work area. In an outdoor area, or near a garage door, set up your welder, a window fan and your workstation. Welding in a well-ventilated area is paramount to safety.
Put the EMT being welded on a working surface. Light a portable torch and burn off the EMT's galvanized coating on all sections being welded. Light the torch with a torch igniter, -- not a cigarette lighter -- and heat the EMT until it turns dark. When cool, sand the areas to a metal finish using 100-grit sandpaper. Wipe down the EMT with a clean rag.
Ready the MIG. First, turn on the welder and check the wire feed speed. Pull the welding trigger and count to six evenly, then measure the amount of expelled wire with a tape measure. If the wire measures 25 inches, add a zero (multiply by 10), which identifies the feed rate at 250-inches-per-minute. This is a normal feed speed. Cut the excess wire at the nozzle tip and discard.
Don all protective gear, including long pants, a long-sleeved shirt, a tinted welding helmet, work gloves and a filter respirator.
Test the welder settings. On a piece of scrap metal, perform a test of the welder. Place the gun to the scrap metal, squeeze the gun trigger and listen for a frying sound. If you do not get the sizzle, turn up the voltage dial on the welder until you do. Also, get used to the weld feed by doing a few practice beads.
Line up the EMT in welding position, holding it in place as required. Begin welding by pulling the trigger when the nozzle meets the EMT, working carefully around the EMT conduit, producing an even bead. Continue until the weld is complete, then release the welding gun trigger. Allow the weld to cool completely before inspecting. Repeat the welding process as necessary.
MIG welding produces toxic fumes. Never breathe in the smoke plumes and have a fan running at all times. Make sure to wear a filter respirator during the entire welding process.