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Hot Rods Welding in a patch panel

Discussion in 'The Hokey Ass Message Board' started by Gus68, Nov 30, 2019.

  1. Gus68
    Joined: Jan 29, 2007
    Posts: 373

    Gus68
    Member
    from Minnesota

    Ok, so here's the deal. I've searched and read lots of posts, but I still have some questions. So here's the bottom line. I have a MIG welder, not a TIG. I've read that TIG is the way to go, but I don't have one so here I am. So for simplicity sake, let's say we are welding in a square patch. I need to have a small gap all the way around correct? Once I have the piece fitted do I place one small tack on each side of the square? Or do I, very slowly, start filling one side in with small tacks? Then work on another side until I'm finnished. I have noticed that even though I have a gap, once I've placed a few tacks , the patch will move and close up the gap. So my thinking is that if I weld all around at the same time that it will try to pull in all directions and distort worse than ever. Oh and I HAVE been trying to smack the tacks while they are still hot but it doesn't seem to change much.
     
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  2. Rex_A_Lott
    Joined: Feb 5, 2007
    Posts: 993

    Rex_A_Lott
    ALLIANCE MEMBER

    Practice on some POS that doesnt matter, try various ways and prove it to yourself. There is no one size fits all answer. Good Luck
     
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  3. brady1929
    Joined: Sep 30, 2006
    Posts: 8,106

    brady1929
    Member

    Criss cross pattern. Otherwise you are putting too much heat in one place that may cause distortion. Go slow and let it cool down.
     
  4. These questions have as many different answers as there are Guys out there trying to do it. I'm a Tig Welder, I'm also over 70 and have been doing this since I was a Kid. I also have a Mig and a Gas torch. Were I doing this job without my Tig unit I'd pick up my torch, install a triple ott tip and some .060 wire long before I'd use my Mig and I'm pretty good with a Mig on the right job. The biggest problem I see in what your trying to do is that it sounds like your trying to LEARN how to do metal work on something you expect to turn out perfect. That isn't going to happen. My advice is to get some scrap and learn how to control what your doing before you take on the patch panel. Some other advice is clean clean clean and on both parts and both sides. You can't weld on rust and not have it cause issues in your weld.
     
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  5. What I do and works for me is to make a patch with the thickness of the mig wire as the gap all around (I use .023") Then I tack around the whole patch alternate sides and I keep them about 1" apart. Then I weld between two of the tacks and cool it with compressed air and then do the same on the other side. On a square patch once I have done all 4 sides I grind the welds down hammer and dolly it out and then weld another 1" between another 2 tacks and do it all over again. For me the trick is getting the patch fit right, keeping the repair cool and not getting in a rush. Good luck
     
  6. You see, I disagree with this. Heat don't cause distortion, it's weld shrinkage that pulls the panel and causes distortion.
     
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  7. anthony myrick
    Joined: Sep 4, 2009
    Posts: 5,043

    anthony myrick
    Member

    Rounded corners are easier to remove distortion in my opinion.
    It really doesn’t matter where you tack weld it as long as it has sufficient tack welds to hold it.
    It’s gonna distort no matter how you do it. However you can make the distortion easier to remove.
    Tack weld, grind, hammer and dolly
    Start connecting tack welds, grind, hammer and dolly
    This works for me
    61F65494-94D7-47CC-9666-D97E4E793EC6.jpeg
     
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  8. Don't make square corners, radius them. Try it and you'll see the difference. Try it on a test piece.
     
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  9. Happydaze
    Joined: Aug 21, 2009
    Posts: 892

    Happydaze
    ALLIANCE MEMBER

    This .

    What's happening here is:-
    tack - causes shrinkage
    grind (just the bead of the weld) - removes bulk of excess material - suggest cut off wheel on its edge
    hammer (on dolly)- stretches metal, removing the shrinkage - difficult with mig as the weld is less malleable - have read some folks apply heat with a blowlamp; presumably this anneals / softens the hard weld?
    repeat ad nauseum!

    I don't necessarily concur with the skipping around thing. Removing shrink as you go should mean that the panel gap is being continually restored. A number of witness scribe marks around the panel (90 degrees to the join) helps keep a check on this by showing the movement (caused by the shrinking, which you stretch back out).

    Saw a cave and pave thing on YouTube earlier, presented in a 'this is how to do it properly' fashion. Oh well!

    Chris
     
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  10. Here is something I have given guys to do when they tell me they can metal finish a panel after welding in a patch. Pick up any piece of sheet metal, I don't care what gauge. Cut 4 strips 3" wide and 12" long. Now weld two pairs of them together on the 12" length. Now weld the 2 pieces that are now 6" together on the 12" length and metal finish it into a single flat panel. There are many processes you can use to get this done and it really don't matter how you get there as long as you do. Until you can do this welding on a curved panel isn't going to turn out the way you want either. The option is to bury your patch work under Body Man in a Can and call it good. Some are happy with that but nobody wants to pay to have that kind of work done. And, yes I can still do it just not as fast or easy as I used to.
    20180328_101041.jpg
     
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  11. Nothing wrong with using a mig welder, everyone is not a pro.

    There is 107 patch panels in the wagon and they were all done with a mig welder.

    Tack your patch in place and alternate from side to side to keep the heat down, and heat will indeed cause the metal to distort. HRP
     
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 44,339

    squirrel
    Member

    Post some pictures of what you've been doing....it'll be ugly, and you'll be embarrassed, but we will be able to see exactly what is happening, and then we can probably communicate more effectively.

    Trying to butt weld with a MIG and then metal finish is pretty challenging. I tend to use a bit of overlap, and I'm not too proud to admit that I use filler over the patch, as well as in lots of other places. Never very thick ,but it's there.
     
  13. Gus68
    Joined: Jan 29, 2007
    Posts: 373

    Gus68
    Member
    from Minnesota

    So, yes, I understand that the weld causes shrinkage, that's why I ask if welding one side completely before starting another side. Yes, skipping around and taking time keeping cool. But Finnish one side before starting another? Or skip around to all 4 sides? My thinking is that skipping around to all 4 sides is gonna make it pull in 4 different directions causing more distortion. Yes I'm sure there will be distortion, but trying to keep it to a minimum.
     
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  14. Gus68, I don't see much difference weather you tack it in place on all 4 sides or weld complete one side. The trick is to keep things under control and don't let it walk around. That can be done by working small sections as you go or spreading it out in multiple places. Mig welding a gap is tough for sure. If that's how you want to do it try using a backer of Copper or Alum. to stop fall through. Some guys are pretty good at that and it does work.
     
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  15. anthony myrick
    Joined: Sep 4, 2009
    Posts: 5,043

    anthony myrick
    Member

    The only way I keep distortion to a minimum is hammer and dolly as I weld.
    With a mig, I grind and hammer and dolly as I progress. With a tig, I hammer and dolly as I progress.
    For me skipping around causes more distortion. I prefer to tac sufficiently enough to properly hold/align the panel. Then weld generally from one end until complete. The stoping to hammer and dolly removes distortion and allows the weld to cool.

    Force cooling makes it worse in my opinion
     
    Last edited: Nov 30, 2019
  16. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 665

    ekimneirbo
    Member
    from Brooks Ky

    Back up a little.......First you need to be sure to use .023 wire because it makes it much easier to weld without making holes. You can poke around with .030 wire but using .023 is better, especially when learning. When you change to .023 you need to change the drive rollers for the wire. Next put the smaller .023 liner in, and then an .023 tip. When welding with .030 wire you can often get by with an .035 liner, but when welding with .023 the wire lacks strength and will tend to make a birds nest if you don't have the correct liner. I'm personally too lazy to do all that switching, so I bought a small 220 Mig with an autoset feature. That way I leave my normal Mig full of .030/.035 wire for thicker welding. If you take the time to set the machine up for thin gage welding it will help you control heat better.

    My non-expert experience is to get a good fit all around.....not tight. Then lightly belt sand the edges just a smidge. Tack it several places opposite each other and check your alignment. Then tack weld several places again and wait a minute for cooling. Don't try to weld one side then the other......just keep adding tacks that are opposite your last tack and maybe do that twice on each side. Then a little cooling and do it again.

    There are as many ways to do this as there are opinions on HAMB, but the main thing is to get a decent fitting panel and use a machine that is set up properly with .023 wire. The suggestion above to try a test piece first is a good one. It doesn't have to be a square, just get two similar thickness pieces and weld them together. Then if your machine needs a little adjustment, you can do it before welding the panel. Your machine should have some kind of reference chart for the settings.

    Once you have the panel in place, grind the weld slowly with cooling periods so you don't put too much heat into the panel with the grinder.
     
    Last edited: Nov 30, 2019
  17. nochop
    Joined: Nov 13, 2005
    Posts: 1,335

    nochop
    Member
    from norcal

  18. Fortunateson
    Joined: Apr 30, 2012
    Posts: 2,703

    Fortunateson
    Member

    I mig and I usually do the alternating tacks on two passes. Then I use a cut off wheel on its edge to grind down part of the weld that is proud. The do the alternating two round grinding process again. I may do it once more depending on the size of the patch. I usually hammer and dolly between rounds as well. Tow thing I have learned is to do teen tiny welds, pin dots, so as not to input too much heat, welding wire that just gets ground off anyway, and take my time. Another tip is if you can get behind the weld use a flashlight to search for those tiny areas that may have been missed. Rocker panels and other lower body areas get a thin smear of fibreglass filler because I'm anal about water getting in.

    My son has a TIG and he's learning how to do sheetmetal compared to heavier stuff. When he's proficient I hope he'll do my welding. LOL
     
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  19. Gus68
    Joined: Jan 29, 2007
    Posts: 373

    Gus68
    Member
    from Minnesota

    I should also say that I have done a little of this year's ago , I sucked then too. So I'm trying to get better at this. I hope to build a 57 chevy into a gasser project. But at the moment I am practicing on an OT S10 for my kid. It'll be for bracket racing. So I hope the traditional police don't show up, but I figure, patch panel is a patch panel.
     
  20. trollst
    Joined: Jan 27, 2012
    Posts: 1,597

    trollst
    Member

    TAKE YOUR TIME, go slow, avoid getting the patch hot, it can take me all day just to weld in a roof panel, lots of patience is required, but you can learn it. Lots of good advise here.
     
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  21. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 1,261

    Lloyd's paint & glass
    ALLIANCE MEMBER

    I mig on a daily basis and i use .030 wire, it's a little more filler in my opinion, but i also keep a wet rag, rung out of course, and i move around with my tack welds until i have a solid weld. Make your welds, and cool them off. That keeps your distortion to a minimum. All my own opinion of course. It works for me.
     
  22. alanp561
    Joined: Oct 1, 2017
    Posts: 891

    alanp561
    ALLIANCE MEMBER

    Do any of you guys do a hot tack and then back up the tack with a dolly and hit the tack once to set the weld? It flattens the weld out considerably and reduces the shrinkage. It helps to have someone else on the back side of the weld to hold the dolly so you can hit the weld while it is still red. You don't have to beat on it, just hit it once and move on to the next tack.
     
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  23. Wanderlust
    Joined: Oct 27, 2019
    Posts: 57

    Wanderlust

    No professional here but I like to alternate front and back if it’s accessable, only ever used flux core .03 wire and dial the feed way back so the wire acts more like an electrode and as much juice as I can get away with and not blow thru, found this to make nice flat tacks with just a little tit poking up on the back. Much less grinding that way and helps keep the distortion to a minimum, also if you can’t hold your bare hand on the panel after say 4-5 tacks your too hot
     
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  24. DDDenny
    Joined: Feb 6, 2015
    Posts: 12,893

    DDDenny
    Member
    from oregon

    I can't add much here but the previous recommendations should get you started, some will work, some won't, like anything you get better with practice and as mentioned, clean metal is key, especially if rust still exists, it's easy to start with clean patch material but the hard part is getting the back side of the metal on the actual body ready to weld, access is the biggest problem but if at all possible the time spent in prepping this area will make the difference in the finished job.
    I'm not gonna say I've mastered mig welding patch panels but I did teach myself to replace the partial quarter on my Suburban which had already been replaced by "stitch" brazing in a used quarter panel section leaving gaps (bad idea) and slobbering it over with bondo.
    These have window drain channels into the inner panel and where the panels overlapped it created a perfect water collection point, slowly pushing out the thick filler.
    Would I do a few things different, sure, that's part of the learning process.
    20180818_163641.jpg



    Here's another good thread on this.

    https://www.jalopyjournal.com/forum/threads/making-patch-panels-that-fit.1139365/
     
    Last edited: Nov 30, 2019
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  25. DDDenny
    Joined: Feb 6, 2015
    Posts: 12,893

    DDDenny
    Member
    from oregon

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  26. Wanderlust
    Joined: Oct 27, 2019
    Posts: 57

    Wanderlust

    Should also add cleanliness and a very good ground is about the most important part, if your getting spatter it’s not clean enough, if the wire starts pushing it’s probably the ground. I work very close to the material 1/8” typically
     
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  27. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,280

    Blues4U
    Member
    from So Cal

    I watched a video once of Gene Winfield welding in a patch using oxy/acetylene torch; he had a helper standing by to hold the torch for him. He would lay down maybe 3/8" long bead or so, hand the torch to his helper, and hammer & dolly the bead flat while it was still red, then move on and lay down another 3/8" long bead and hand off the torch to the helper and hammer & dolly it, then repeat the process till he was done.
     
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  28. 49ratfink
    Joined: Feb 8, 2004
    Posts: 17,505

    49ratfink
    Member
    from California

    if heat does not cause distortion how come you can warp a panel while grinding? ..
     
  29. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 1,261

    Lloyd's paint & glass
    ALLIANCE MEMBER

    Lol its the same principle as heating a nut to get it off of a bolt. When it's red, it expands, when it cools, it shrinks. Same with the grinder.
     
  30. 49ratfink
    Joined: Feb 8, 2004
    Posts: 17,505

    49ratfink
    Member
    from California

    I recommend having two projects going on at once, leaving plenty of time between tacks so they can cool. heat is the enemy.

    heat also occurs in the grinding process, so I use the side of a cut off wheel on my air grinder and only attack the weld and leave the surrounding sheet metal alone. I had a buddy who liked to grind welds with those flap wheel sandpaper things. he chopped a top on an F-1, and ground the whole piece where his welds were paper thin with dozens of tiny pin holes. I bet I could have poked a screwdriver through the metal. don't do that. watched him shave a door handle on a car, then warp the door grinding the weld. don't do that either

    I'm sure there are people out there getting perfect work with a mig, but I am not one of them. I never go in with the thinking I can fix it with bondo after welding, I figure if you go in not looking for perfection you will never find it. that's how I do it and sometimes it actually works.
     

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