when to plug, seam or gap weld

[BrokenBiker]

when welding cars how do you know when to either plug weld, fully seam weld or do seam welds spaced apart i.e. Inch long weld, inch space, inch long weld etc

obviously a repair to an outer panel needs fully seam welding, but what about when doing a resto job and having to deal with inner and outer sills, inner arches, floor pannels, bulkhead etc.

 

[ben8vgte]

I work on the principle that if it was spot welded at the factory then I plug weld it, chopped in repair a panel then a seam, stitch weld I just use for reinforcement on spot weld seams.

Trouble with just tacking or stitching in a repair piece is water can in from the back rust under any filler and fall out, that and I prefer the tig for seam welds as it's less work to clean up afterwards.

 

[BrokenBiker]

so to fully replace a sill you would spot weld, for things like arches you would spot weld them in the stitch for reinforcement?

 

[ben8vgte]

Well a sill I plug weld the bits that were spotted, but seam the other bits where they join to the panels. Most cars the sill would of been part of of the whole side pressing, replacements are much smaller bits. Arches are the same but more seam welding normally.

This sill was plug welded top and bottom, but the where it meets side panels ect are seemed.

Red Astra by ben a.k.a me, on Flickr

Red Astra by ben a.k.a me, on Flickr