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Thread: How clean is clean enough?

  1. #1
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    How clean is clean enough?

    I've welded 52+ years. I've come to a point where every weld gets a pre arc grind. Most of my welds are stronger than the application needs, so I grind until shiny.

    Today's project is a new trailer hitch on a 28000 LB GVW truck. The trailer is 23000 LB GTWR.

    I will attach the hitch to two crossmembers built a year ago by the man who fitted the dump body. He used new steel, primed & painted.

    I'm under the truck over a 66" deep grease pit, I'm standing on the third rung of a stepladder grinding it clean where I will Dual Shield weld it. After grinding all the paint, all the mill scale, I still see black veins in the steel.

    Should I grind until there is nothing left? Or, will Dual Shield overcome some impurities. Factory steel is NOT flat. One has to grind pretty deep to get past all the texture.

    When do I stop grinding?
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  2. #2
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    Re: How clean is clean enough?

    Quote Originally Posted by Willie B View Post
    I've welded 52+ years. I've come to a point where every weld gets a pre arc grind. Most of my welds are stronger than the application needs, so I grind until shiny.

    Today's project is a new trailer hitch on a 28000 LB GVW truck. The trailer is 23000 LB GTWR.

    I will attach the hitch to two crossmembers built a year ago by the man who fitted the dump body. He used new steel, primed & painted.

    I'm under the truck over a 66" deep grease pit, I'm standing on the third rung of a stepladder grinding it clean where I will Dual Shield weld it. After grinding all the paint, all the mill scale, I still see black veins in the steel.

    Should I grind until there is nothing left? Or, will Dual Shield overcome some impurities. Factory steel is NOT flat. One has to grind pretty deep to get past all the texture.

    When do I stop grinding?
    I usually clean rust and paint with a really nasty stiff bristled cup brush in a 5" angle grinder and then hit it with a hard disc. Small imperfections will burn out just fine.

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  4. #3
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    Re: How clean is clean enough?

    Quote Originally Posted by 12V71 View Post
    I usually clean rust and paint with a really nasty stiff bristled cup brush in a 5" angle grinder and then hit it with a hard disc. Small imperfections will burn out just fine.
    Dual Shield is a product I've had success with sometimes. Out of position, a mountain of weld to place, I want to use dual shield. Someone suggested cutting down my contact tip to allow more stick out, better gas coverage. I tried it. In test runs I got only a small bit of worm track first arc, the hose might not have been completely purged.

    First real weld has to be good, I'm going to chance it. I feel there should be a limit to grinding when 3/8" steel gets down to 1/4, it might be too far.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  5. #4
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    Re: How clean is clean enough?

    Same as 12v71, the reason welding filler material isn't just hot rolled round bar is partly the deoxidizers for dealing with some impurities.
    Last edited by ttoks; 10-16-2021 at 07:55 PM.

  6. #5
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    Re: How clean is clean enough?

    Quote Originally Posted by Willie B View Post
    Dual Shield is a product I've had success with sometimes. Out of position, a mountain of weld to place, I want to use dual shield. Someone suggested cutting down my contact tip to allow more stick out, better gas coverage. I tried it. In test runs I got only a small bit of worm track first arc, the hose might not have been completely purged.

    First real weld has to be good, I'm going to chance it. I feel there should be a limit to grinding when 3/8" steel gets down to 1/4, it might be too far.
    When it has to be absolutely positively shielded on the the first trigger pull, I run 3-4" of wire and clip it off where I like my stickout. Purges all the lines and the gun.

  7. #6
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    Re: How clean is clean enough?

    Dual shield is a lot more tolerant about rust or scale than hardwire. If it's mostly shiny without loose rust your good.

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  9. #7
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    Re: How clean is clean enough?

    Quote Originally Posted by 12V71 View Post
    When it has to be absolutely positively shielded on the the first trigger pull, I run 3-4" of wire and clip it off where I like my stickout. Purges all the lines and the gun.
    I clicked the trigger 10 or more times, no wire feed. I thought I was purged, but first weld had a single worm track. I was at 40 CFH 75/25. I turned up to 45, no tracks. I'm now set at 50 CFH, a trailer hitch is important!
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

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    Re: How clean is clean enough?

    Quote Originally Posted by Willie B View Post
    I clicked the trigger 10 or more times, no wire feed. I thought I was purged, but first weld had a single worm track. I was at 40 CFH 75/25. I turned up to 45, no tracks. I'm now set at 50 CFH, a trailer hitch is important!
    Something to keep in mind is that those surface worm tracks you get with dual shield don't affect the welds mechanical properties at all, when doing the oil and has stuff with dual shield it made no difference to the Charpy v notch test numbers at any temp, the rockwell hardness, X ray/gamma ray (as long as the worm tracks were ground off the top) or tested yield or ultimate tensile strength, or elongation.

    What brand of dual shield wire are you using?

  11. #9
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    Re: How clean is clean enough?

    I've noticed that grinding steel with primer and paint often leaves little lines of primer/paint residue. Never have had them develop any weld defects. Never been a fan of grinding where base metal thickness is reduced.
    Chris
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  13. #10
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    Re: How clean is clean enough?

    Quote Originally Posted by milomilo View Post
    I've noticed that grinding steel with primer and paint often leaves little lines of primer/paint residue. Never have had them develop any weld defects. Never been a fan of grinding where base metal thickness is reduced.
    I go over it several times. I work with hard disc from closest to farthest, get the paint off. I go back one more time to get residue. Then I use a 40 grit flap disc. Finally, I go at it with a non woven (Scotchbrite) style. Most paint residue is gone. It's the texture in the steel, (might have rust deep in the voids), but everything on the surface is clean.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  14. #11
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    Re: How clean is clean enough?

    Damn Willie, that's a lot of cleaning for dual-shield

    For stick or self-shielded wire, I just hit it with a hard wheel and then get to welding.

    For solid wire mig or for tig I do a lot more.

    I can't imagine the dual-shield wouldnt work about the same as self-shield and stick?
    Dave J.

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  15. #12
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    Re: How clean is clean enough?

    Quote Originally Posted by MinnesotaDave View Post
    Damn Willie, that's a lot of cleaning for dual-shield

    For stick or self-shielded wire, I just hit it with a hard wheel and then get to welding.

    For solid wire mig or for tig I do a lot more.

    I can't imagine the dual-shield wouldn't work about the same as self-shield and stick?
    OK, you talked me into it, not that I have much over the top of my head grinding left in me anyway.

    If it's a success, I'll be bragging later. If a fail, I'll be very very quiet!
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  16. #13
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    Re: How clean is clean enough?

    Can you cook it out?

  17. #14
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    Re: How clean is clean enough?

    Quote Originally Posted by tapwelder View Post
    Can you cook it out?
    Not much cooking happens with Dual Shield. Laying down filler is fast.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  18. #15
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    Re: How clean is clean enough?

    Quote Originally Posted by Willie B View Post
    Not much cooking happens with Dual Shield. Laying down filler is fast.
    I meant with torch, preweld

  19. #16
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    Re: How clean is clean enough?

    Quote Originally Posted by Willie B View Post
    OK, you talked me into it, not that I have much over the top of my head grinding left in me anyway.

    If it's a success, I'll be bragging later. If a fail, I'll be very very quiet!
    I understand that very well
    There are no pics of my failures
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Syncro 350
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  21. #17
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    Re: How clean is clean enough?

    Quote Originally Posted by tapwelder View Post
    I meant with torch, preweld
    Oh, perhaps.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  22. #18
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    Re: How clean is clean enough?

    I just gotta ask.. what brand of Dual Shield wire are you snarling up constantly ?

  23. #19
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    Re: How clean is clean enough?

    Quote Originally Posted by lars66 View Post
    I just gotta ask.. what brand of Dual Shield wire are you snarling up constantly ?
    I can't say. It's a pressboard reel, label is gone. I went into Maine Oxy. They had Lincoln & another well known brand I can't remember. He said a local welder, (member here) used a lot of it, refuses the other brand. I believe I have Lincoln.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  24. #20
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    Re: How clean is clean enough?

    Quote Originally Posted by MinnesotaDave View Post
    I understand that very well
    There are no pics of my failures
    Oops... Had to undislike this post. Dislike was an accident. My fingerpad has a mind of it's own sometimes.

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  26. #21
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    Re: How clean is clean enough?

    I find the stick out on dual shield doesn't make much difference like hard wire. So dont worry to much about that. I like it close. Really close on hardwire, the closer the better

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