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Hammers and dollies and files. Oh my!

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  • Guest's Avatar
    Guest replied
    "You may change your mind about O/A when you have to repair a large panel where you can't get in behind to dolly it. The metal shrinkage from O/A welding can be frustrating, especially with the thin metal used on more modern vehicles."

    I agree 100%. I know MIG is the way to go in that situation. To do things right in autobody work I would think a person should have a MIG welder and an O/A outfit. They each have their places.

    I've O/A welded 2 pieces of sheet metal together and watched the pieces rise like butterfly wings as the filler metal cooled.

    If you can't get to both side of the weld you can't make it flat.

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  • torker
    replied
    Dan, this thread brings nack some not so fond memories
    I took an autobody course some time ago.
    One of the first things we had to do was cut out a piece of 20 guauge and fit it into this funny looking 18" square box frame.
    Oh boy...now we had to take hammer and dolly and beat on that thing until it was up 1 1/2" in the center and a near perfect dome. Not so bad...ooops...along comes the ol' instructor and makes us heat and shrink the whole thing down to a 1" drop so it looked like a big salad bowl.
    Hmmm...that took a day.
    Then we had to raise the whole darn thing up again. When it was near perfect 1" high dome again....the ol' jerk comes along and drives a sharpend chipping hammer right through it.
    So, then you get to repair the hole with O/A and shrink/stretch the whole thing back into the 1 1/2" high dome. When it looks good then you finish the surface off with body files and lead until it's perfect.
    Whole process takes over a week.
    The entire north wing of the college just hates panel beating time.
    You can imagine the noise when 25 students are hammering(and cursing) for over a week.
    You may change your mind about O/A when you have to repair a large panel where you can't get in behind to dolly it. The metal shrinkage from O/A welding can be frustrating, especially with the thin metal used on more modern vehicles.
    Russ

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  • Guest's Avatar
    Guest replied
    CCWKen,

    No, he didn't mention a shrink disk. And he didn't mention doing any metal shaping (as in fabrication).

    There are only 14 class sessions so I can understand why we won't get into metal shaping but I'd really like to learn more about it.

    I did mention in another thread how I had a chance to play with plastic hammers and a a leather shot bag. I then played around with the English wheel. But that stuff was all on my own.

    I wish they had a whole class on sheet metal fabrication.

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  • CCWKen
    replied
    <font face="Verdana, Arial" size="2">One of the guys ended up with an 'oil can' dent. The instructor fixed it with an O/A torch.</font>
    Did he also mention the shrink disk? It's also a good way to shrink--Without a torch. The only problem with a disk is that it craps the paint. But if you're hammering and filing, there's not much paint.

    I finally got my power hammer up and going again. It's shrink dies work magic. Will your class include any metal shaping? (Making a panel from scratch)

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  • Dawai
    replied
    I built and installed probably three stitch timers into Mig welders.

    Pull trigger, one thousand, two thousand three it cuts off. Operator adjustable.

    You have to move around or you ruin the panel. It has more ripples and does not fit anymore. Not even a quart of bondo will make it better.

    AND THE CHINA REPOP hotrod parts suck.

    HTRN: yeah. I had a 69 camaro that would pull one front wheel. It cracked the windshield pulling that trick.

    I'd fasten the seat belt, open the door and lean out and look at the tire, Stomp it, the tire would grow taller by inches, one wisp of smoke would come over the top, then the tire would dissapear. Then, you were going 60 and had better sit up.
    That one had a mild 327, powerglide, Vega tork Convertor, a gear set and a few other goodies. It was rippled like a waffle.
    The 4-bolt 350 I had in SEVEN cars would wheelstand the monza. I still have the engine stuck back. The monza - Iroc 5 speed got the valve springs. You could not shift fast enough to keep it out of redline.
    I kinda wish I had that car back. I'd lose my license for sure.

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  • Guest's Avatar
    Guest replied
    Sandy,

    Yep, we covered that issue also.

    I've seen in some books that HSS (high strength steel) panels should never be repaired but replaced. Apparently, since this guy was a GM instructor, GM teaches otherwise.

    He did caution not to overheat large portions of HSS panels.

    What I'm seeing is that they repair just fine but they are terribly thin so O/A is more difficult to use than MIG when welding panels.

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  • Sandy H
    replied
    pgmrdan,

    I agree that O/A is amazing in its versatility. I just took a welding class and enjoyed more of the O/A than stick and mig combined. The instructor said that in general, though, keep O/A away from newer cars. He said the large heat affected area tended to weaken the high strength alloys they are using more today.

    Just something he said that could be worth mentioning. I'm not sure how important it really is, though.

    Sandy.

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  • HTRN
    replied
    Dave ain't kidding. One of the better tricks for street racing was to look at the rear quarters because the opposition isn't going to open the hood - they'res money involved afterall.

    You avoid the cars with the rippled quarters. I've only seen that twice, one was a big inch(500+)NoX fed Box nova. It was reputed to be the fastest street car in the entire borough.


    HTRN

    ------------------
    This Old Shed

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  • Dawai
    replied
    My fist has popped more dents than I think I have with a hammer.

    Metal does have a memory. If you get down and sight down the fender thou, it remembers the dent.. ha ha..

    A hotrod with a lot of horsepower twists the whole body. Makes the body look like crap.

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  • DR
    replied
    Years ago I bought a truck with a fairly large dent on the front fender. Although the dent was deep there was only slight creasing around part of the dent's perimeter. Because of the inner fender, the outer skin had to come off to be pounded out.

    After the fender was off it was lunch break time so the fender was left on the grass in hot sun.

    An hour or so in the hot sun and the dent almost totally fixed itself. At first I was sure one of my smart ass neighbors had fixed it while I was eating.

    Memory of the metal??

    The crease around the dent was so slight I put it right back on and it was hardly noticeable.

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  • Guest's Avatar
    Guest replied
    I mentioned a little while back about the instructor popping a dent with an O/A torch. He didn't touch the fender. He just spiraled the torch well above the sheet metal and the dent raised up and was gone.

    He said he's fixed new cars after a hail storm doing this type of thing and the paint wasn't affected.

    With the oil can dent he actually shrank 3 spots with the O/A torch to fix it.

    I know that when it comes to cars people just love MIG machines but an O/A outfit has plenty of uses too, probably more.

    [This message has been edited by pgmrdan (edited 01-31-2006).]

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  • Dawai
    replied
    Dry ice will work as well as a torch.

    I watched a guy with awe. he had a block of Dry ice going around and around hail damage dents. The dent got smaller and smaller then dissapeared. Paint was not affected.

    Ask the instructor about this.

    They total out cars with extensive hail damage.

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  • Guest's Avatar
    Guest replied
    One of the guys ended up with an 'oil can' dent. The instructor fixed it with an O/A torch. Good as new!

    Amazing stuff.

    I know it takes a lot of practice to get good at it and the instructor makes it look really easy. But some of the techniques seem to be fairly easy but not something you'd come up with on your own. I'm glad I'm taking the class.

    [This message has been edited by pgmrdan (edited 01-31-2006).]

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  • Dawai
    replied
    I remember hammering on a Road Runner fender. A guy came in, Asked What are you doing? I replied playing with my pecker. I had named my favorite hammer woodpecker.

    I chased that dent from one end of the fender to the other several times. The car had a supercharger on a 440/4speed, would twist the body up like a pretzel and I was worried about a lil dent.

    Now, I feel privilidged just to have touched it. It wasn't mine, but it kept coming around for me to work on. You had to sit on the fender and squirt gasoline into the carbs to crank it when cold. The rich kid would drag it down the shop, I'd crank it and then he'd go play around Chattanooga. I don't know what he did when I left the area for a while. It probably is sitting in a garage somewhere with dust on it.

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  • Guest's Avatar
    Guest replied
    Gee Alistair, you must have been in my class last night! You gave a perfect descritpion of how to fix a dent.

    [This message has been edited by pgmrdan (edited 01-31-2006).]

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