When to plug weld when to seam

[Springerdinger]

Can someone throw some light on mot rules for me please on patch repairs.
My understanding was that if it was a patch repair then it had to be a full seam weld. If it's a panel replacement and it was spot welded then it is ok to plug weld.

I have seen a few patch repairs that have been plug/spot/puddle welded and it is confusing me.

I have also seen full panels replaced, that have been seam welded when plug/spot welding was probably suitable.

Could someone who knows more about this than me write a few guide lines

Cheers
Chris. The mediocre diy and slightly confused mechanic

 

[the snooper]

imagine you buy a brand new sill and chop a square out of it then put that square back in all 3 cuts would have to be seam welded but the bottom flange you could still spot weld.

in any repair if there is a spot welded flange you can spot weld it, if its a hole in a panel that used to be a whole piece and no spot welded seam then you would have to seam weld it all the way round to make it 1 piece again

 

[Springerdinger]

imagine you buy a brand new sill and chop a square out of it then put that square back in all 3 cuts would have to be seam welded but the bottom flange you could still spot weld.

in any repair if there is a spot welded flange you can spot weld it, if its a hole in a panel that used to be a whole piece and no spot welded seam then you would have to seam weld it all the way round to make it 1 piece again

That's a great explanation
thank you.
Cheers
Chris

 

[BrokenBiker]

I was always confused with this until I was told by my mot guy 'if it looks like it did originally then it will pass' so if I'm patching the middle of a panel it gets a full seam and ground back to flat, if it's a full panel it gets attached the same way the old panel was attached (which is why I love the bolt on wings on my Alfa)

 

[norsa]

As a general rule in MOT law, and im talking patch repairs here not panel replacement, if its within 300mm of a chassis area, (which includes steering and suspension pick up points) it has to be a continuous seam. However. if part of the patch repair involves a dry seam where it was originally spot welds, you can reproduce those.
Nick

 

[anjum]

imagine you buy a brand new sill and chop a square out of it then put that square back in all 3 cuts would have to be seam welded but the bottom flange you could still spot weld.

in any repair if there is a spot welded flange you can spot weld it, if its a hole in a panel that used to be a whole piece and no spot welded seam then you would have to seam weld it all the way round to make it 1 piece again

Wot if you cut the square out in the centre??? Just joking! Very good explanation/ example.

 

[the snooper]

Wot if you cut the square out in the centre??? Just joking! Very good explanation/ example.

then there would be 4 cuts not 3