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  1. #1
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    Default Mig Welder Gas/Gasless Metal Thickness

    I am seriously considering purchasing a shielding gas cylinder for mig welding. One thing I would like to have cleared up first.

    My BOC Smootharc 175 welder can go down to 17.5v when mig welding. At this setting, using gasless it can burn thru thin metal with ease (2mm). My question is how does this relate to using a shielding gas. Will this welder be able to weld thinner metal at this setting without burning thru it or should it need a lower setting. I would be mostly using steel down to 1mm thick.

    Dean

  2. #2
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    You really should be able to handle 2mm with gassless wire - I did a heap of 2mm wall gal tube with my UniMIG 165 using gassless wire before I went to CO2.

    Assuming you're using 0.8mm wire, at 17.5V you're a little above what you'd want for a MIG mix gas, but might be OK on CO2.

  3. #3
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    Quote Originally Posted by RustyArc View Post
    You really should be able to handle 2mm with gassless wire - I did a heap of 2mm wall gal tube with my UniMIG 165 using glassless wire before I went to CO2.

    Assuming you're using 0.8mm wire, at 17.5V you're a little above what you'd want for a MIG mix gas, but might be OK on CO2.
    I would have thought it the other way around, as I thought CO2 gave better penetration. When I weld thin stuff I go fairly quick with MIG, using argo/CO2 mix.
    Kryn

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    Quote Originally Posted by KBs PensNmore View Post
    I would have thought it the other way around, as I thought CO2 gave better penetration.
    With CO2, the lowest useable setting is about 17V, whereas with a MIG mix it'll run down to 14V or so, which makes welding thin sections easier.

    I gotta say, I'm a bit surprised the BOC doesn't go any lower than 17.5V.

  5. #5
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    Thanks guys. I still have a disposable CO2 cylinder. I will give that a try and maybe also buy a mix to try. I am going to be disappointed myself if I cannot do thin stuff still.

    Dean

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    Quote Originally Posted by RustyArc View Post
    With CO2, the lowest useable setting is about 17V, whereas with a MIG mix it'll run down to 14V or so, which makes welding thin sections easier.

    I gotta say, I'm a bit surprised the BOC doesn't go any lower than 17.5V.
    Sorry I misread your reply, fingers in motion before mind into gear
    Kryn

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    Quote Originally Posted by KBs PensNmore View Post
    Sorry I misread your reply, fingers in motion before mind into gear
    Kryn
    I just went to a MIG mix from CO2 and am finding the new settings a bit odd, but the lower volts for the same thickness steel explains why it's a bit more civilised that with CO2.

    All that said, for the few bits I've done with this mix (Speedgas Speedshield 5/2 Ar/CO2/O2) the difference to straight CO2 isn't exactly night and day.

  8. #8
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    A look at the spec sheet for my welder tells me
    MMA 20 to 175A
    TIG 10 to 175A
    MIG 50 to 175 A

    Dean

  9. #9
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    Update.

    I finally managed to try my welder with gas (CO2) today. I am currently working 6 x 12hr weeks (nightshift).

    First I had to adapt this welder to fit the small disposable cylinder, and regulator that came with my previous mig. The reg had a push in 4mm poly pipe fitting. I found an equivalent fitting that would swap with the larger fitting on the back of the welder. I had to pull it apart to do this.

    I have a 1kg reel of ms solid wire also left over from the previous welder that had not been opened yet. My current welder only takes 4.5kg reels. I had an empty 4.5kg reel so I decided to wind the wire on to it. It is wonderful having a metal lathe with a VFD. The chuck jaws fitted inside the bore. The live centre and a bit of suitable round with a hole thru it held the reel in place. Mounted the 1kg in the toolpost with some all thread etc and away we go. Easy.

    Welding was totally different in terms of burning thru the metal. No issues at all with that. A hissing sound rather than a crackle. The wire is 0.6mm tho, and I only have 0.8mm tips. I am not sure how much that will affect it. I will order some 0.6mm and have another go. The weld seemed to build up on top of the metal too much. I got up to 20.5v and the only difference was a higher weld. The weld did not penetrate thru 1mm sheet. There is still some work to do to get it right. The weld is nice and smooth. I backed the gas off until the weld looked horrible, then increased it again.

    Any suggestions would be welcome. I have a flow meter, but I would need to get hold of some fittings to convert it to fit to 4mm poly.

    Dean

  10. #10
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    Have you swapped the polarity of your welder? Solid wire runs DC electrode positive, whereas gasless runs electrode negative.
    "A hissing sound rather than a crackle. The wire is 0.6mm tho, and I only have 0.8mm tips. I am not sure how much that will affect it. I will order some 0.6mm and have another go. The weld seemed to build up on top of the metal too much. I got up to 20.5v and the only difference was a higher weld. The weld did not penetrate thru 1mm sheet."
    That worries me a bit. Welding with gas should give a crisp crackle like bacon frying in a hot pan, a hiss means insufficient wire for a given voltage. Increasing voltage should flatten the weld, not heap it up as you describe.
    According to the the Lincoln welding parameters, using .6 solid wire and CO2 on .9mm steel, you would run around 16V, with 2.8 m/min wire speed.
    A bit of a dodge that can help with oversize tips is to slightly bend the tip as this encourages better contact with the wire.



  11. #11
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    Quote Originally Posted by Karl Robbers View Post
    Have you swapped the polarity of your welder? Solid wire runs DC electrode positive, whereas gasless runs electrode negative.
    "A hissing sound rather than a crackle. The wire is 0.6mm tho, and I only have 0.8mm tips. I am not sure how much that will affect it. I will order some 0.6mm and have another go. The weld seemed to build up on top of the metal too much. I got up to 20.5v and the only difference was a higher weld. The weld did not penetrate thru 1mm sheet."
    That worries me a bit. Welding with gas should give a crisp crackle like bacon frying in a hot pan, a hiss means insufficient wire for a given voltage. Increasing voltage should flatten the weld, not heap it up as you describe.
    According to the the Lincoln welding parameters, using .6 solid wire and CO2 on .9mm steel, you would run around 16V, with 2.8 m/min wire speed.
    A bit of a dodge that can help with oversize tips is to slightly bend the tip as this encourages better contact with the wire.

    Oops! That would be a NO! Thanks Karl. I will try again tomorrow. When working long hours like I am at the moment your brain can be a bit reticent. That's my story anyway.

    Dean

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    An older fellow I worked with told me that the best sound to hear, better than the oft quoted frying bacon, is the sound of continuously tearing paper. That's the magical sweet spot.

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