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Question about welding patch panels?

Discussion in 'The Hokey Ass Message Board' started by sled51merc, Dec 27, 2003.

  1. I'm welding a patch panel that's about 8 inches long and 3 inches wide on the bottom of a fender. There is a curve involved and I'm having a hell of a time getting the patch panel formed just right to fit the curve. My question is, when welding the patch in is it best to tack the whole patch in at different spots or should I concentrate on one side at at time. Thanks in advance for any advice.

    sled
     
  2. Andy
    Joined: Nov 17, 2002
    Posts: 4,594

    Andy
    Member

    You have to get the patch to fit great to start with. Hold it in place and tack it in a couple of places. Hammer the welds if it doesn't fit right. Tack some more and check fit. As the welds cool, they shrink. If you hit them with a back-up behind the weld, it expands the tack. If you expand too much, heat again. Don't ever loose the shape. It will never come back. Keep tacking and hammering untill it's very well covered. Weld up using short weld lengths and skip arround. Hammer the weld to expand the weld out to the original shape. Don't hammer when the weld is hot. Always wait until the pannel is at room temp. Don't put water on it. Just let it cool between work.
     
  3. I'm using a MIG welder, does that matter as far as hammering on the welds? Also, is it bad to cool welds with water, if so, why?

    sled
     
  4. Andy
    Joined: Nov 17, 2002
    Posts: 4,594

    Andy
    Member

    You only hammer the welds enough to get the shape of the pannel right. If the welds did not shrink much then little hammering will be required. Throwing water on the pannel can warp them and it does make the metal harder.It is much better(and slower) to just let it cool.
     
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  5. 30roadster
    Joined: Aug 19, 2003
    Posts: 1,793

    30roadster
    Member

    Andy is probably saying that cooling the weld with a wet rag will work harden the weld. you want a soft weld to hammer. cooling it when it's cherry red is a bad thing....but helping it finish cooling after a few minutes isn't going to do too much. i'm not sure it will matter with a mig? ... any opinions?
     
  6. Are you welding this over top of a spot or did you put the patch up to the fender and trace around it and then cut it out to weld it flush with the panel? Flush is best, but not the easiest. You also need to tack the panel on all sides alternating back and forth to keep the heat from building on any one area. If you weld only on one side you will end up with the patch twisting. Don't try and weld a too long a bead either as it will cause warpage. Easy way is to keep tacking all the way around. No major heat, no major warpage. Welding frames and welding in bodywork are 2 different animals. The only way to be a good welder is practise. Have at it.
     
  7. Andy
    Joined: Nov 17, 2002
    Posts: 4,594

    Andy
    Member

    30roadster is right. If the metal has lost all color and is getting close to room temp, then a little help is all right. You just don't want a lot temperature difference when the metal can deform.Quenching a hot weld can cause a lot of problems.
     
  8. Morrisman
    Joined: Dec 9, 2003
    Posts: 1,600

    Morrisman
    Member
    from England

    I spent ages cutting, trimming and curving a panel to patch a hole in the edge of my roof. I tacked it in, tacked some more, and so on. When I'd finished I carefully ground it all flush, and noticed the patch had 'sunk in' about a 1/16" all over!!!!???? [​IMG] [​IMG] [​IMG]
    After asking around I found that I shoulda pounded on the tacks to stretch them back to size, with a dolly behind obviously, as and when I did them, rather than just leaving them be.
    I later did a door panel repair and carefully tapped on each set of tacks, and all came good [​IMG]

    Been down to help a buddy chop his Ford popular roof today [​IMG].
    Paul
     
  9. Since this post was posted today, it may not be too late to save you.

    Put your patch panel on the infected area. Just lay it on ther like it goes. Now, measure down an inch and cut it off there. If you have to go verticle, measure an inch as well and cut that crap as well. Now, put your patch panel up ther like it should fit, mind you, you'll be overlaping an inch of metal, on the top and sides, fit it nice, and tack it in place. It fits really PERFECT right? Ok, grab youre 9.95 harbor frieght grinder with the THIN BLADE and cut 1 inch in the center of the panel, right at the edge of the new patch panel. Grab the MIG and put a tac or two. Go a couple inches over and do the same. Make sure your new patch is even with the oreginal body panel. When you have the patch taced all the way, the 1 inch excess should come off by pulling on it. Let each tac cool by its self, and use vice grips to alighn it and hold it solid as you go.
     
  10. Don't want to seem to dumb Rogue, but I'm having a hard time understanding your suggestion. I haven't tried to weld the patch panel in yet, figured I'd wait till' tomorrow. I cut the panel so it would fit flush, though I might need to cut a new piece since I think it could fit a little better. I've always been told that flush is the best way to weld in a patch panel. Is there anything that you could add to your post that would help me understand it better. I've never heard of doing it this way but I'm interested in what you are saying. Thanks for your help!

    sled
     
  11. Don't mean to make you sound dumb, kinda hard to explaine.

    Lets say you lay your patch panel were it goes. Now, draw arond the edge of the patch panel, like you were gunna cut it there, but don't cut it yet. Take the patch panel back off the car and draw a new line 1 inch below (or if it needs a verticle cut) 1 inch on the inside of it. That is your cut line.The 1 inch excess metal that will now be behind your new patch panel will hold the shape as you weld. It's like a backer.

    Now, grab your vice grips and clamp it into place. Make sure you have it perfect. That 1 inch overlap is really nice to clamp to so clamp the panel in the center using two clamps with about 4 inches inbetween them. Get your cut off wheel and cut between the clamps right at the edge of the new patch panel. You should have a small gap (1/16th) between the patch panel and origenal part after you make the cut . The 1 inch overlap should now be cut in the center of your new cut and pryed away from were your gunna weld. Once you got that overlap away from youre weld gap, reposition the clamps to be 1 inch apart in the center of the cut and align the two pieces of metal. They should be flush and the panels will have no distortion. Now put a tac between the clamps, let it cool for a coupel of seconds , then reposition the clamps and do that again a couple inches away from that spot. If you do it this way, you will finish quickly and have a pretty strait piece.When you finish, that 1 inch backer should be off the car. I guess you could say cut as you go.......
     
  12. Rogue, thanks for elaborating some more on your other post. I understand it alot better now. Thanks to everybody for their help.

    sled
     

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