Re-Tigging a mig weld

[raveboy2012]

So what's the theory behind this? Is it to re melt the pool thus fixing the micro fissures that seem to be inherent with mig welding without the need for extra metal?

 

[backpurge]

It is sometimes done to ensure complete fusion at the toes of the weld which can be a bit suspect with MIG, have only ever seen it specified once in 40 years, obviously would not be suitable for all materials and would probably cause problems on thin material

 

[zardoz]

I would guess the only time you would want to do this is to re do a poor MIG weld, when it is for some reason not practical to MIG again from the begining.

 

[raveboy2012]

Hey guys Thanks for your responses, I posed the question as I had read about it on here and having recently completed some external sill work I noticed some micro fissures when I ground back.

 

[backpurge]

See explanation of process below, knew I'd seen it somewhere, not really suitable for what you were talking about
http://www.onepetro.org/mslib/servlet/onepetropreview?id=OTC-3466-MS