I decided to open a new thread for my arc welded sill repair, ahead of an MOT. Here are 'before' and 'after' images. More photos to follow, covering other aspects. These tack welds and short bursts were done with a cheap Chinese DC inverter welder. I could have used my AC transformer buzzbox almost as easily but the DC inverter is better for striking arcs. I'm delighted to have made fair progress in using an arc welder to patch up quite thin, rusty old metal on the bodywork of my car. A MIG welder would probably have been quicker but this job is definitely achievable with a cheap arc welder, as I hope I have now shown. All these welds were either vertical or upside down, neither of which I'd tried before. Generally, though, I'd urge anyone to test and practise on scrap metal before starting work on a car. Use the same types of metal, same gear, same rods, same settings - test everything in advance. I will probably now try and run a weld bead along each side of the plate. The extra metal provided by the tacks and short bursts should make this possible without blowing holes.
As Archie said on the 'real world' thread: "George you could save yourself a lot of hassle by letting us cast our collective eye over a couple of your welds. Those what know would be able to tell you whether the work is likely to pass the MOT or not.
So, now I've posted two photos, will these tacks and short bursts pass the MOT if left as they are?
Wozzaaah said: "Pigeon poo might fail...if it's insufficiently fused but as long as the tester is satisfied that it's sufficiently fused to the parent matal and there are no gaps then he should pass it."
Malcolm said: "Well done! I'd have thought an MOT inspector would accept that. The continuous seam rule is to stop repairs that have only been tack welded in place (a tack every inch). I'd imagine yours in the photo would count as continuous. The risk of using multiple tack welds is you don't get enough heat in to a fair percentage of the weld, and that's especially a problem if the surface isn't clean (yours looks well prepared but I've bought patched cars where people haven't bothered). Bit of rust between the sheets can be enough to pop the the tacks, and of course strength (crash) wouldn't be quite so good.
I then said: "Malcolm - thank you for your kind words. I try to be very thorough in terms of (a) cleaning the metal back to bright shiny steel before I start and (b) removing every last scrap of slag after each 'batch' of tacks or any other weld. Now I've built up the depth of metal with so many tacks, I can almost certainly try to run a seam without blowing holes. Perhaps a seam 'cap' would provide the extra heat and penetration which you refer to. Thank you also for all your tutorials. Although primarily aimed at MIG welding, I found that many of your tips also apply to arc welding. Also, I used two plug welds on the lower edge of my repair panel where it was in line with the thicker chassis 'rail'. I would never have known about plug welds, the size of drill to use, or anything without your help.
As Archie said on the 'real world' thread: "George you could save yourself a lot of hassle by letting us cast our collective eye over a couple of your welds. Those what know would be able to tell you whether the work is likely to pass the MOT or not.
So, now I've posted two photos, will these tacks and short bursts pass the MOT if left as they are?
Wozzaaah said: "Pigeon poo might fail...if it's insufficiently fused but as long as the tester is satisfied that it's sufficiently fused to the parent matal and there are no gaps then he should pass it."
Malcolm said: "Well done! I'd have thought an MOT inspector would accept that. The continuous seam rule is to stop repairs that have only been tack welded in place (a tack every inch). I'd imagine yours in the photo would count as continuous. The risk of using multiple tack welds is you don't get enough heat in to a fair percentage of the weld, and that's especially a problem if the surface isn't clean (yours looks well prepared but I've bought patched cars where people haven't bothered). Bit of rust between the sheets can be enough to pop the the tacks, and of course strength (crash) wouldn't be quite so good.
I then said: "Malcolm - thank you for your kind words. I try to be very thorough in terms of (a) cleaning the metal back to bright shiny steel before I start and (b) removing every last scrap of slag after each 'batch' of tacks or any other weld. Now I've built up the depth of metal with so many tacks, I can almost certainly try to run a seam without blowing holes. Perhaps a seam 'cap' would provide the extra heat and penetration which you refer to. Thank you also for all your tutorials. Although primarily aimed at MIG welding, I found that many of your tips also apply to arc welding. Also, I used two plug welds on the lower edge of my repair panel where it was in line with the thicker chassis 'rail'. I would never have known about plug welds, the size of drill to use, or anything without your help.