OK just ruined V3.0 Better than the last one but still warped the edges. I clamped it with a piece of 1" square tubing in about 5 spots down the length as I welded the top and bottom. I've got the heat turned as far down as it will go and still melt metal. I've been using one wet rag laying across the inside and another small one to quench each spot after my weld. I even tried rolling a bead around the opening to see if that would help control the warpage but still not flat. Somehow I must still be getting it too hot!!!
I wonder if a different type of filler rod with a lower melting point would help? I've often noticed that when TIGing mild steel with this rod it tends to be sticky (not wanting to fully puddle) and I have to get it right on top of the tungsten to get it to melt.
Or I just need to get better at my metal working to straighten out the edges...
I think I will try some 16g for V4.0 And I do have some aluminum bar laying around that I will try for the clamping next time.
Has anyone tried that Eastwood welding heat putty?