How tight ?

[gryan39]

Learning mig with hope of repairing few rust patch on old camper.
Got few old panels to practice on.
Is it best to try get new cut metal tight as possible. Ie no gaps or leave a 1mm gap all round. Thanks.

 

[Morrisman]

Leave a small gap for the weld to creep into. That way you get a better weld, plus if you grind it smooth you're not taking all the weld off.

 

[mike 109444]

Or as you have a practice panel, check out "fitzee's fabrication" on YT for the cut n butt methord.

 

[Erie Fred]

Practice, practice, practice.
Set up same material thickness as the job, try the different gaps, orientation (vertical, horizontal, flat), settings etc.

 

[JOEPRO]

Yes leave a 1 or 2mm gap for sure. Welds will always shrink and pull the metal locally. Not allowing for this could lead to excess oil canning effect on panels.

Best to weld in tacks inch apart to start with allowing to cool gently each time then start tacking in the gaps. I use an air blow gun to cool mine as I go and keep the heat down as much as possible.

 

[gryan39]

Cheers guys. Ye been practicing. Found a local steel supplier yesterday who sells off cuts to the public. He's in govan glasgow incase anyone local to that and needing stuff

 

[Onoff]

Fitzee on YT shows how it can be good to make a 45 degree cut. Makes sense when you watch it.

 

[julianf]

I find it best to try and make the panel a tight fit and then fill in my resulting error with weld!

 

[Morrisman]

Don't be afraid to experiment with different power and wire speed settings. First car project I did I got fixated on high wire speed to get the 'crackling bacon' sound everybody told me I should be hearing. It was pants, wire kept shoving through the weld, weld sat proud, no penetration etc.

Then one day a mate came round and told me where I was going wrong. A bit of practise with half the wire speed and I was amazed just how well a mig can stick thin steel sheet together. This was the result, dozens of patches, a complete new floor, 4 door converted to 2, and 3" out of the roof. Worked out okay I reckon.