Mig Welding Technique For Thin Tube Welding

So I thought you might need to see some mig welding on some thing tube. 

Well the story is that we bought a brand new kids trike. The back axle has some threaded rods welded to the thing gauge tubing.

The problem was that when I tried to push the solid rod through the tube the rod only went in about 5 inches. Where they had welded the threaded rod onto the pipe they had blown through and all the molten metal had built up inside the tube. And of couse this was the reason why the rod would not go through the tube.

So the solution was to cut the tube in half and then clean out the weld.

I used my metal cutting band saw and made a nice clean and neat cut through the thin walled tube. I made sure that I held the majority of the weight of the band saw cutting arm in my hand. Otherwise the blade may have totally hacked the tubing and I may not have got a clean square cut.

Then I used a five inch angle grinder and a wire wheel to clean up the painted surfaces.

One of the biggest critical areas for welding thing gauge material is poor fit up. So it was very important that I made sure that the pipe was cut square and that the two bits were clamped together. I inserted the solid rod into the tube and then clamped it all up with the vice grips to hold it tight.

Now onto the mig welding technique. The best way to tackle a job like this is to use a series of spot welds or tack welds.

If you work around welding in opposite places you can lower the heat input and heat affected zone. So what you do is start at the 12 o'clock position then go to the 6 o'clock position then the 9 and 3 o'clock positons and slowly work your way around.

The machine power settings need to be adjusted so that it runs hotter. You need enough power to have instant fusion with the metal. So turn up the power to way higher that what you would have normally set it to if you were going to weld this.

You will see that there is a big blog of weld spatter stuck to the side of the work. This is the blog or ball of molten mig wire that is left over when you let go of the trigger on the mig welding gun. As this need to be a clen a tidy weld what you have to do is snip off the end of the wire. If you do not it can like in the photo and the video stick to the metal you are welding.

Here you can see in the photo how the welds came out. And then what it looks like after it was clean up with the angle grinder and wire brush again.

I ended up putting two coats of red enamel paint on it and it came up really good. Now I could put the brand new trike back together.

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