I am trying to patch in a fender lip on a restoration project. I read through the archives before attempting hoping to try and eliminate any warpage. I was 100% successful on other areas of the car (rockers, quarters etc). I couldn't have asked for a better result. However these 2 (right & left) fender lips have me stumped. In the attached photo the circled area is where I get the warp. If I cut the patch where you see the black lines, about an inch on the vertical and 1 to 2 on the horizontal the panel returns to its original shape. I am about to try a third attempt but figured I would end up with the same result. Is there some thing I can do differently to get a better result? I am using a Lincoln MIG. I have taken a ton of time to keep the heat build up at a minimum. I don't understand which way the metal is moving to try and prevent the warp. It sucks that a 2" weld can screw up a decent panel when the first 10" didn't affect it at all.
Thanks- Mark
So when you cut the panel, the gap created from the cut probably expanded a bit more than the thickness of the blade used and that allowed the panel to go back into place.
If this is the case, its telling you that you need to planish, (hammer and dolly) the weld to stretch it out some.
The metal at the weld has shrunk causing the distortion further away.
Do not tap the metal at the warped area. As you slowly planish the weld, you will see the problem disappear.
Does it matter if the weld is hot? I work alone so it's tough to tack it and then hammer. I have read that the weld needs to be glowing. Also, should I tack, hammer, let cool, and repeat? Or hammer when its all welded in?
Thanks for your help.
I was under the impression it was welded twice already and was currently welded.
Do not reheat the area again is you've done it twice already. Planish (cold) along the whole weld and watch your problem area to see if it starts to pop back.
I hope it's OK if I jump in here, "123Pugsy" is correct...I will try and explain how things like this happen...when you weld, you create heat, the heat expands the metal, when it cools it shrinks more than it expanded when it was hot. So, when you planish the metal (hammer and dolly) what you are doing is stretching the metal back to it's original thickness. Think of it this way...might sound stupid but it may get the point across...when you tenderize a steak by hitting the meat, the steak gets thinner, but it also gets wider...(sorry but it's the only similarity I could think of at the time). When the metal is back to it's original thickness the warping should be minimalised. Metal has memory, but when it's heated it stretches as it cools it shrinks causing metal to loose it's memory, when you use a hammer and dolly your giving your metal a reminder as to where it used to be.
I agree with pugsy, do not make any relief cuts or do any work anywhere except on the weld itself. If you are quick enough to planish the weld while it is still hot it will reduce the chance of cracking, but that is history now that its already welded. Do not reheat.
I prefer gas or tig but in the future its important to make sure the patch fits perfect before welding, and with a mig just do a spot here and there and let them cool naturally.
When planishing cold, grind the weld bead almost but not all off the front and back, then put a dolly with a similar contour on the back side and hold it with a good amount of pressure to the weld and strike on the dolly with firm blows up and down the weld area, you should hear the ring of the hammer hitting the dolly. You will see when it starts getting close to the right contour, then start using a straight edge, and keep raising the lowest areas. Its not that difficult, you can do it, good luck.
Allow me to jump in with a question. I've been working with scrap body metal trying to gain some kind of feel for welding in patch pannels. When I start the hammer dolly work on the patch, do I concentrate my work mostly on the weld? Is my hammer face smooth or or dimpeled?
I've had some success shrinking oil can spots using my dimpled hammer and dolly, but they do not leave the metal silky smooth by any means. I ended up cutting this piece out for other reasons unrelated to the hammer and dolly work.
A 28 oz carpenters waffle head is good for building houses, the theory behind a waffle body work hammer was that you could hit with a glancing blow to move metal. I don't use one. I try to keep all my body hammers polished by working them on the back side of my 6 X 48 in. belt sander
you can allso use a propain torch like a plumbers just heat the center of the low and cool it quich with a cold wet cloth it will shrink the metal if you do it right and stop the oil can
The problem with stretched metal is realising just exactly how much stretch is involved.
Most times the heat/quench method is just too much.
On hail dents, the metal is surely stretched, but the dents can be easilly removed with a pencil torch, and not quenching. Sometimes without even damaging the paint.
hmmm...never tried that. Outta give it a try. We just had a Subaru that had hail damage and it was worst on the hood. No matter how light I tried to shrink the stretch the work kept spreading and spreading. One tiny dent ended up being an area of filler almost 1/4 of the hood. Then again, you forget how flimsy and sensitive the newer metals are when you constantly work on hot rods. I'm thinking that pencil torch could have helped me some.
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