Automotive Welding

  1. puffernutter

    puffernutter Puffernutter

    Messages:
    1,158
    Location:
    Wiltshire
    I'm not new to welding, just not very good at it! My first introduction was a stick welder on an apprenticeship course in 1980. I have a MiG that I use for repairing cars. Nothing flashy and I use 0.8mm wire. I also have a TiG that I haven't even played with yet!

    I am a hobby welder and for various reasons periods between welding can be very infrequent, I have an abrasive doofer on the wire that cleans it before it hits the rollers, so it should take any oxides off.

    I prepare the area to be welded and get it as clean as possible and I also get as good an earth as possible.

    BUT

    I still either fail to get penetration or blow holes! So what should I adjust, wire speed or current. I can eventually get a good weld on the new metal and new metal to new metal, but generally fail with the new metal to car!

    I have a Triumph Spitfire I'm working on and I've put a lower rear wing pane on and its OK, but not something I'm that proud of and will require a lot of time with a grinder, then filler :-)

    I know it's experience, but that's not going to happen in the near future, so how do I balance wire speed/current (or voltage in this case!) I get the "sausage sizzling" noise, so I assumes I was doing something right and I use an intermittent approach to stop me overheating one area!

    I know the theory, it's the practice that let's me down :-)

    Cheers

    Peter

    P.S. I'll be asking about how to TiG and whether I should learn that to do these repairs in the TiG forum sometime later.....
     
  2. james butler

    james butler Member

    Messages:
    1,206
    Location:
    birmingham england
    if your welding thin stuff, as a starting point you would be better off with thinner 0.6 wire.
    i also have problems welding thin car body work, all you can do is make it easier on yourself by following some of the tips found here
    http://www.mig-welding.co.uk/thin-metal.htm
     
  3. james butler

    james butler Member

    Messages:
    1,206
    Location:
    birmingham england
    another thing is metal prep.
    on the origenal metal work of the car are you getting back to good metal or just clean the rust of damaged metal?
    if you clean rust off damaged metal and try and weld it you will allways blow holes in it, i appreciate that sometime more metal than you would like would have to come out but it makes a huge difference to the quality of the weld.
    also are you using sheilding gas and if so what type of sheilding gas are you using?
    ive read on here somewhere that CO2 gives a hotter weld so more likely to blow through on thin stuff.
    the type of welder you have can also make a difference, my old sealey welder was great on nasty rotten metal but the portamig i have now is completely intolerant to it.
    odd but it does seem to differ between the two.
    settings wise i find a fairly low setting and just do half inch bursts moving quickly and leaving gaps so the metal to cool and then finish them off on a second pass
     
  4. addjunkie

    addjunkie Member

    Messages:
    5,067
    Location:
    Northumberland. Reet oot in the sticks
    Ok I hate welding cars, vowed never to do it again 25 years ago, and to this date only twice since.

    I used .8 wire, and do a series to tacks, working around the joints so it doesnt get too hot. Just over lapping the tacks. Max run id do would be say 1/2 an inch, any more and im through. If it starts to distirt, tap it back and off you go again.

    Get comfy....get so you can really see what your doing, if you need glasses to see wear them to weld. I then to use both hands too to get the torch as steady as i can. Cleanliness is next to godliness with tin on cars.

    Did I say I hate welding cars.
     
  5. p0689109 Member

    Messages:
    1,660
    Location:
    stoke on trent,england
    I stick weld my cars. Less to worry about except the essentials, clean metal, correct size rod and tag and run until panel is attached then join the tags. If possible use a heat sync on the back. I also find the inverter stick welders are better as they do not tend to stick on striking unlike the transformer ones. Of course cleaning old metal of all rust and stuff often leaves it too thin and so cutting back to sound metal is the option.
     
  6. pedrobedro

    pedrobedro Man at Matalan

    Messages:
    9,754
    Location:
    CX Derbyshire
    You're my hero :D I use .8 wire and have done since the first roll of .6 ran out with my first welder about 40 years ago. I wouldn't stick weld anything much under 5mm.
     
  7. Burdekin

    Burdekin Chief Bodger

    Messages:
    4,573
    Location:
    Aberdeen
    Got some pics you can post up Peter?

    What fit up are you using?
     
  8. rikrobson

    rikrobson Member

    Messages:
    3,698
    Location:
    Perth, Scotland
    I dont use .6 any more. I have more problems with .6 than .8 wire. The secret is managing the heat effectivlt. Set it up so you get good penetration on the metal and just do short bursts of welding and join up the dots and grind back afterwards.

    Dont be tempted to do long runs youll end up putting too much heat in and blowing through. Also the mote heat the more the panel will want to warp.

    Also i find co2 to fierce for thin stuff and use 5% co2 mix gas
     
  9. puffernutter

    puffernutter Puffernutter

    Messages:
    1,158
    Location:
    Wiltshire
    I use a Murex Transmig 140. Its electronics had recently had a diagnostic and is 100% OK. I'm loathe to go to 0.6 as I do other welding and it is so much faff changing tips, rollers re-threading etc.!

    I will take some pictures when I get a chance. The Spitfire is outside at the moment under wraps, we've just had a litter of puppies and that is and will take all of my time for the next 2-3 weeks!

    For the last panel I created a joggle and spot welded through the hole. I still seemed to have problems getting the penetration between the two and I took the car back to goo metal and cleaned it properly. I know the problem with a joggle is that it is a place for damp to collect and rust out and ideally I should solder the gap!

    Trouble is, when I try to but weld, I blow holes and then there is no easy way back!

    Cheers

    Peter
     
  10. puffernutter

    puffernutter Puffernutter

    Messages:
    1,158
    Location:
    Wiltshire
    I use the Argon/CO2 mix from BOC as the shield gas.
     
  11. Richard.

    Richard. Member

    Messages:
    18,044
    Location:
    Cambridgeshire
    Penetration is all deemed around the current you draw for a given wire size*
    Current is primarily controlled by wire speed and will also vary with stickout.
    Other variables like active gases and your travel rate will effect the amount of heat you put in but assuming you try to keep most things the same I'd suggest you play with wire speed.
    Set a voltage setting that gets you in the ball park and set a low wire speed. Do a run on a non backed butt joint then turn the wire up a fraction. Do it again. Repeat this till you burn through then set it back a touch and your not far off a decent penetration setting. Bear in mind burning through is inevitable on thin automotive body work and a perfect world doesn't exist in this line. This is when technique with stacked tacks comes in.
    *its a common misconception that a smaller wire diameter will penetrate less and help you out. Quite the opposite. While a 0.6 wire will carry the low current better its tiny diameter and reduced arc width over a 0.8 will penetrate deeper under the same dip transfer condition. In spray it won't but in dip it will be more likely to burn through and make gap bridging more difficult. Personally I've used both and 0.8 is the my own personal choice for such work.
     
  12. gt6s Member

    Messages:
    696
    Location:
    Newtownards Co Down Northern Ireland
    But Spitfires only rot between the bumpers. Include the bumpers. As you see by my username I am big into Gt6's for 26 odd years now. Welder wise I am truely spoilt my Sureweld 161 will weld to any unpreped surface except scale and is so easy used. I run .6 all the time even to build my welding table at full power wire speed well turned up. I had no .8 having a good machine makes a huge difference.

    Laurence
     
  13. gaz_moose Member

    Messages:
    937
    Location:
    tamworth staffordshire
    i would use the stitch weld feature on that machine, set the current hotter than most and over lap the welds to give the 'stack of dimes' effect like you get with tig welding. you want the 'cool down' time to be enough for it to stop being cherry red.

    use 0.8 wire.
     
  14. HughF

    HughF Member

    Messages:
    5,333
    Location:
    Work: Dorchester, Workshop: Corfe Castle, Wife's place: Frome
    I'm happy to pop over sometime if you want and cast an eye over things, I'm only up the road remember (most weekends)... You might be doing something obvious that we can change to get things going better for you.
     
  15. puffernutter

    puffernutter Puffernutter

    Messages:
    1,158
    Location:
    Wiltshire
    Thanks for the offer - I have a piece to weld on the bonnet - that would be a good opportunity to see what I'm doing wrong!

    It may be a few week, with puppies and dog shows, but I will be in touch!

    Thank you.

    Cheers

    Peter
     
  16. HughF

    HughF Member

    Messages:
    5,333
    Location:
    Work: Dorchester, Workshop: Corfe Castle, Wife's place: Frome
    I go past most weekends and often wonder what you're up to :) Keep in touch
     
  17. Wozzaaah

    Wozzaaah The wizard of woz Staff Member

    Messages:
    14,281
    Wiltshire, UK
    Don't forget I'm only the other side of town too, more than happy to pop round any time.
     
  18. HughF

    HughF Member

    Messages:
    5,333
    Location:
    Work: Dorchester, Workshop: Corfe Castle, Wife's place: Frome
    Mini-gettogether at PufferNutter's then :)
     
    slim_boy_fat and Wozzaaah like this.
  19. Burdekin

    Burdekin Chief Bodger

    Messages:
    4,573
    Location:
    Aberdeen
    Have a gander at Peter Tommasini's video on gas welding: Tig is the same process, you need access to both sides of the panel so you can planish (hammer on dolly at the weld) the weld. I also use an airline to cool the weld after each weld. The aim with tig welding is to get your fit 100% with no gap and then you can just fuse weld the repair in and then there is no requirement for grinding after. If you get your fit up perfect with no gap then tigging is the easiest welding you can do, about 20amps, torch nice and perpendicular and then just push the puddle along. You can't do long runs as you put too much heat in the panel so therefore you don't need to be a good tig welder to tig car panels, you just need to know the technique, be super fussy on your fit up and understand what the heat and planishing does. With tig you can get perfect repairs with no distortion, it is slower if you don't get your fit up right though.
     
    james butler and galooph like this.
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