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Chopping top weld inside or outside?

Discussion in 'The Hokey Ass Message Board' started by 1930ModelA, Mar 10, 2013.

  1. 1930ModelA
    Joined: Sep 4, 2008
    Posts: 109


    I have a question about chopping a top. I am chopping my 30 model A coupe. What is the best way to weld it back up. Should I weld it from the outside or the inside? I am going to tig it.

    Thanks for any advice
  2. Flatheadguy
    Joined: Dec 2, 2008
    Posts: 2,037


    If you weld it on the interior side then you will have a mess on the exterior. I have not heard of anyone welding a chopped roof on the inside, but I suppose someone out there may have done it. Why does this question come up? I don't understand.
    And, be sure to skip weld. Not one continuous bead. A series of tack welds. No longer than a bit more than a tack. And go back and forth. Take your time, Minimum heat.
  3. 1930ModelA
    Joined: Sep 4, 2008
    Posts: 109


    Flatheadguy thanks for the response. I have this question after reading an older rod and custom article on chopping a Model A where they welded from the inside. I have never seen this method either.

    I am gettting ready to do mine here in two weeks and just getting everything ready for the job.

    Any other opinions would be greatly appreciated.
  4. tinmann
    Joined: Nov 11, 2005
    Posts: 1,589


    if you are a decent tig weldor, the inside and the outside are going to look the same, so weld from the outside for better access. Welding is only one part of the overall equation. Hammer and dolly work is every bit as important as the welding.
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  5. BarryA
    Joined: Apr 22, 2007
    Posts: 643


    x2 what Tinmann said
    If the welds are good it shouldn't make any difference - other than being a little harder to weld upside down unless you have a rotisserie.
    It is all about keeping things under control - weld as slow or fast as you like, as long as you are able to stretch the seam back out where it has shrunk you will be good. Skipping around doesn't mean less distortion overall (that is simply a function of how much heat goes in), but it does help to stop it getting away from you - as long as you hammer on dolly and bring it back to neutral as you go.
    Good fit up and consistency of the heat band you're putting in, is more important as this will make your shrink more predictable and controllable.
  6. Beau
    Joined: Jul 2, 2009
    Posts: 1,883


    I used MIG on a panel. The weld penetrated enough to look the same on the opposite side. I ended up alternating sides ever couple inches and skipped around after each bit cooled. It all ground down the same.
  7. I would think the outside would be the best approach,,HRP
  8. The37Kid
    Joined: Apr 30, 2004
    Posts: 26,936


    Is INSIDE the inner part of the A & B pillar? Somewere Pete Eastwood posted some top chop welding info. He cuts the outer skin maybe two inches above and below the chop cut line, this allows you access to the inner structure. Welding the INNER as well as the OUTER makes for as as stock strong joint. Bob
  9. I guess if you are laying some strengthening pieces in the pillars then welding inside is necessary.
  10. mcmopar
    Joined: Nov 12, 2012
    Posts: 1,540

    from Strum, wi

    Never done it myself, but I would weld outside for ease of welding and cleanup. I never thought I would read this much about dolly's on a car board.
  11. toreadorxlt
    Joined: Feb 27, 2008
    Posts: 733

    from Nashua, NH

    tig weld outside, hammer and dolly straight. Thats how i do it. In an ideal world, you'd have no gap, no filler rod, and just planish it straight. thats really hard to do.
  12. Noland
    Joined: Oct 16, 2007
    Posts: 1,237


    Yes this is the correct way to do it in my opinion. Its not good to just weld the outside tin. you need to weld the inside post. this goes for any chop or modification that consists of mutliple stacked panels. you want to weld everything you possibly can not just the outside tin.
  13. Outside so you can grind it smooth.
  14. alchemy
    Joined: Sep 27, 2002
    Posts: 15,325


    I did a huge reassembly job on a '32 roadster body decades ago with a MIG, and did as much as I could from the inside. Instead of grinding it away, I was able to leave most of the bead for strength.

    My Bros and I practiced our TIG welding on reassembling a '31 coupe a few years ago and we did some from inside and some from outside. As said before, a good TIG weld should look about the same from both sides. Not as much bead height, so grinding isn't a problem.
  15. b-bob
    Joined: Nov 4, 2008
    Posts: 1,097


    My first reaction was if you have good penetration then there would be no need to weld on the inside too. Of course that's where it is a single panel, but yes you do have to go inside for all the multi-layered posts and flanges.
    I always weld up my edges first, like door posts, windows, so they don't move during the rest of the welding. And don't forget to weld in reinforcement bars in side the door openings, and side to side, and bolt the body to the frame with the door gaps lined up.
    And as already been said, if it starts to warp on you, stop and make it right before continuing. Good luck and take your time.
  16. I see a lot of B/S about welding on a chop here,most are well intended persons I am sure but Bullshit just the same......

    All this hoopla about reinforcing the cut seams with inner bolster plates and welding on the inside are a total waste of effort and in no way help save your life in a wreck.
    An average Mig-hot spot weld that penetrates to an equal place on the metal's thickness is capable of [ERS-70 WIRE[corrected]=70,000 lb per square inch shear-strength.
    Plus of course you Tig guys welds, are stronger even yet-right?

    If your weld is adequately hot and penetrates adequately, your simple butt joint on all posts will be at least as strong as the surrounding metal is.
    I mean whats next? making all post cuts at a 60 degree angle to posts-because an angled splice is stronger than a 90 degree splice?

    Also if you consider the old addage"-long stick short stick"....a shorter roof pillar is actually stronger than the taller posts were, once welded back together.
    Lets face the hard facts guys=
    not a one of the many thousands of chopped tops I ever saw or heard of anyone chopping [however sloppy]-tore off in a wreck and hurt anybody......never.

    That is what I call proof positive....Lets dont over anal=ize our hobby into an anal pissing contest needlessly......
    If you can prove otherwise Im listening......
    Last edited: Mar 11, 2013
  17. toreadorxlt
    Joined: Feb 27, 2008
    Posts: 733

    from Nashua, NH

    if you are truly looking for a metal finish, more filler metal is not the answer.

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