Introduction: Converting a Flux Core Welder to a Mig Gas Welder

About: My name is Louis L. a Knife maker and so much more. Make sure to check out my Instagram @bitterbladeco and my YouTube Bitter Blade Co.

So I picked up this Hobart flux core welder on Letgo, and I really wanted to turn it into a Mig Welder using shielding gas which would give me cleaner welds with less splatter. This welder didn't have any valves or fittings to accommodate a gas bottle so I had to wire and install a gas Solenoid. Some welders have all the tubes and fittings so this process wont be necessary in some welders but mine was lacking the necessary parts so here is how I did it.

These tube and fitting sizes were for my welder, different brands and models may need some different tubing.


Wire stripper/ crimper





Gas Solenoid 115v AC (1/4" npt)

1/4" OD tube

3/8" OD tube

Gas Tank (75% argon 25% Co2) (for MIG welding applications)

Gas regulator for tank

electrical connectors

Barb fittings (1/4" npt)

1/4" OD to 5/32" OD in line adapter

Angle push to connect fitting (or more barb fittings)

Teflon tape

Solid mig wire

Step 1: How to Tell If Your Welder Is Gas Compatible

There are a few ways I know my welder can be converted to a gas mig welder and these same features need to be on yours to accommodate a gas cylinder.

1. There are 2 empty terminals on the circuit board inside the welder. These empty ports are shown on the electrical diagram/ schematic on the inside of the welder shown as "Optional Gas Valve".

2. There is a plastic plug covering a hole in the back of the welder. This is the port for the fittings to exit the back of the welder.

3. There is a tube coming out of the gun and into the welder, This tube on my welder was 5/32" OD. It should be tied into the wiring harness coming from the gun.

Step 2: Plumbing and Routing the Solenoid

Following the the arrows on the bottom of the solenoid, on the "In" side I screw in a barb fitting with teflon tape that goes to the regulator on the tank. On the "out" side of the valve I screwed in a 1/4" npt to 1/8" npt adapter. Into the adapter I screwed in a 1/4" OD push to connect 90 degree angle (1/8" threads). A tube (1/4" OD) comes out of this connector to a 1/4" to 5/32" reducer. Then this goes to the tube coming from the welding gun.

Step 3: Mount Solenoid in Welder

For mounting the solenoid I had to reposition the fuse reset to make it fit. I drilled 2 small holes in the back case of the welder, then I wrapped wire around the valve and twisted it together pulling the solenoid tight against the back case of the welder.

Step 4: Wiring the Solenoid

I stripped the 2 wires and crimped the ends with blue female connectors coming from the solenoid. I attached them to the circuit board and pressed the trigger on the gun to make sure I could feel the valve clicking.

Step 5: Switching Electrode Polarities

This step is very important. On the side of the welder with the wire spool are the electrode and ground terminals. The inside of the welder should state the orientation of these contacts for flux core wire and solid Mig wire. This needs to be correct or else the welder will not run correctly.

Step 6: Start Welding!

Open the valve on the tank and get to welding! Thanks for reading! If you want to see a step by step video I have it linked in the beginning of this Instructable.

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