Welding different thickness steels

  1. Turbogn Member

    Posts: 7
    I have gotten down welding two pieces of steel of the same thickness but my buddy wants to weld an oxygen sensor nut to his exhaust pipes on his car. What would be the best way to do this? The Exhaust pipe is very thin while the nut is very large and very thick. How should I set the machine up? Where should I aim the wire when welding. Favor the nut or favor the pipe? Anyone have any tricks to offer. Thank You.
  2. Wozzaaah

    Wozzaaah The wizard of woz Staff Member

    It's not critical strength-wise so as long as it's on there and doesn't leak exhaust gases, that will suffice.
    Favour the nut rather than the pipe, just concentrate the wire onto the nut and allow the weld to lap onto the pipe.
  3. Turbogn Member

    Posts: 7
    Thank you for the advice. One last question please. I have a Lincoln 120 volt mig. Since it can only weld up to 1/4" MAx. Would I have the machine set on max since I will be directing the wire on the nut?
  4. Wozzaaah

    Wozzaaah The wizard of woz Staff Member

    Not really, the nut won't be going anywhere so it only has to be held in place and not leak. Gat any old nut roughly the same size as the one you're going to use and have a bash at welding it to a piece of thinnish steel, you'll soon find what settings works best.
  5. scarecrow

    scarecrow Outstanding in his field

    Posts: 1,628
    You will need to turn the heat up as the nut will act as a heatsink you don't need full penetration on the nut as the joint will only be as strong as the thinnest material like Woz said to a little practice first
  6. gavuk

    gavuk artful-bodger

    As Wozz says do a practise join ,its not hard to weld the nut ,too much heat and you run the risk of over penatration,or distorting the threads ,not a major problem if u have a tap to put through the nut when cooled down
  7. drivewasher

    drivewasher Member

    Posts: 375
    There is a link on here somewhere to a training vid. That shows a guy using a plumbers blowlamp to heat the thicker metal (in your case the nut) this allows more penetration on the nut as it's already at a higher temp than the thin steel plate(exhaust) Iv'e tried this and it does work!

    Hope you get the gist of what I mean
  8. drivewasher

    drivewasher Member

    Posts: 375
    You could leave a bolt or threaded bar in while you weld. This will also help in clamping work together IE the bolt head is ideal for a glamp finger. use a long bolt and leave it sticking out so you can access around the nut to weld
  9. chevyman_de

    chevyman_de Forum Supporter

    Thread size on oxygen sensors is usually M18 x 1.5, so don't scew up with the wrong bolt.
  10. JayRS4

    JayRS4 Si vis pacum, para bellum

    Posts: 930
    Woking, UK
    I`ve been doing quite a lot of this lately, i`ve found a bit of preheat on the thick piece helps no end. Doesnt need to be much, i`ve only been using a smallish blowtorch.

    You should be able to get a bung to fit in there, should help with distortion, i`ve got a copper one, but I rather need it and wouldn`t knwo where to get another i`m afraid. Somewhere that sells the sensors might be able to help you.
  11. simon718

    simon718 needs to stay off ebay

    Posts: 2,015
    Norn' Iron
  12. chevyman_de

    chevyman_de Forum Supporter

    Sure, but any dead oxygen sensor would do as well...
  13. Hitch

    Hitch Moderator Staff Member

    Posts: 10,486
    Last thing you want to use would be a stainless plug.

    Just concentrate the weld onto the nut, then wash the pool onto the exhaust.
  14. TIG Paul

    TIG Paul Moderator Staff Member

    Posts: 4,077
    Northampton. UK
    I wouldn't put anything in a nut whilst welding, if the nut shrinks and pinches the bolt or plug you''ll never get it out, run a tap through after welding if needed.
  15. chevyman_de

    chevyman_de Forum Supporter

    Neither would I. That's because I usually don't feel a need for it. I've welded many nuts and the bolt always went through fine without running a tap through the nut before. That means to me that a bolt in the nut while welding would not have bee pinched. The tolerances are usually big enough. Just don't weld the complete circumference at once.
    But you're right, when Murphy strikes you can prepare for desaster.
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