Hello together, first I have to say thank you to all the people here wich share their work and building up old cars. I like watching people creating metal parts so I have a question to all the metal fabricators here and we have a lot. When you build a repair panel (such as a bottom part of a door) you lay the new part after its bent on top of the old part to see if it flushes everywhere. How do you weld in the repair panel to the door without the metal to fall in by the weld? As I build the repair panel on my 46 Buick door the panel layed perfect on the door. The first few weldings and it was still ok. After welding they rounding of the door was shrunken and the door didnt have the perfect rounding any more. Regards Marcus
If the welds are soft enough, you can use a hammer and dolly to stretch them. Should reduce the shrinkage problem.
What do you mean with soft welds? I welded with a Mig welder. There was no room to reach the middle part of the door
Not sure if you welded all across the door in one pass or not. You should skip around only making a spot weld on one side of the door and move well away from that spot to allow the area to cool while continuing another spot weld possibly on the other end of the panel. Heat buildup will shrink the panel. It's all about controlling the heat across the panel as a whole if that makes sense to you.
Shrinkage is one of the biggest problems when mig welding sheet metal panels together. When you weld, the metal is hot and is at max expansion, as it cools it shrinks, so you can hold a dolly behind and hammer from the top to stretch it back to shape. with your door it may be hard to get a dolly inside but you can just weld small spots skipping from one area to another but you must let it cool between welds. I don't know about over there but in the US you can buy "soft" mig wire to make it easier to hammer out. Tig welding reduces this problem as the heat affected zone is smaller and it uses a more controlled heat.
Thnks Rmonty. I laid a wet cold cloth next to weld to hope the metal not to worm up to much. But thanks for ypure advice. I have the other door to repair. Il try it!
Make short welds like RMONTY said. It looks like you will have a hard time reaching the back side of the weld area to hammer and dolly it back out. When you weld a bit and that weld cools off it shrinks and pulls the two pieces together a bit. That is what has pulled your “rounding” out of your panel. Those mig welds tend to be a little harder than the surrounding metal when they cool but if you grind them down without heating them up again you can manage to put the shape back in the door. You may have to pry them up from inside the door so that you can hammer and dolly them back to shape by hammering on the outside of the door. I hope you can understand what I’m trying to say. The main thing is don’t give up. Sent from my iPhone using The H.A.M.B. mobile app
I just now read your thread on the car build. After seeing that, I have no doubt you can handle the work. Did you rebuild the inner and outer portion of the door? Sent from my iPhone using The H.A.M.B. mobile app
I rebuild the bottom inner portion of the door in two parts first and welded them to the door to make it more stable. After that I built the bottom outer skin. I knew I would have a problem with hammering the weld from the inside because there is no room (about 2 1/2 in the middle of the door. Perhaps it would of been easier if I had cut out the middle section of the inner door. Its not to bad fallen in you wount see it because the fadeays will cover the door, but its in my mind not havent it perfect. I have seen lots of fabrication here where you dont even see the weld anymore. Only a perfect surface. So Im always willing to learn
The old school method of welding or repairing panels was oxyacetylene torch hammer and dolly welds , as an example Gene Windfield still uses this method , I once did a panel repair with flux core wire that came with the machine since I ran out of gas and the welds stayed malleable and easier to grind again heat control, been welding over 40 years all kinds of metals
Instead of welding the inner structure first you could cleco or screw it to the door temporarily to fabricate and fit your outer panel. Turn the outer flange lip on the outer panel to only a 90 degree bend. After you rehang the door and are satisfied with the gaps, then pull it off, remove the inner structure piece and weld your outer skin on. This will allow you room to properly finish the welds on the outer skin. After you are happy with that you can then weld on the inner structure. Then fold over the outer skins lip that was pre bent at 90 by way of hammer and dolly. It's a bit more work and you may have to have the door on and off a couple times but it will yield the results you are after.
I find its best to weld the seam continuous if possible. Very minor tacks, close together to hold it and then weld in a single pass.
MIG welding makes a harder weld than Oxy or TIG welding. Do you have access to a TIG welder? Hammering the welded area back into shape after welding is a major part of the process, and limiting the ability to do this by MIGing is going to reduce your good results. But there's always Bondo.
Is welding a door or roof part better with a TIG welder or with a acetylene welder. When using a Tig welder do prefer using a copper additive or without?
I do some tig, but im still more comfortable with mig for most of my old rust repairs where the new metal is joining old, contaminated metal. I just go real slow, start with a few tacks, and keep adding to it while taking breaks in between to let it cool. door skins especially can be risky, especially if it starts to shrink and "valley" at the seam, it will be pretty noticeable and hard to correct since the backside of the skin is usually pretty obstructed with the inner door frame/ sheet metal. theres some more stuff in the thread in my signature, but I grabbed these for the doors on my '37 Buick. all mig welded, just slow going and cleaned up with the edge of a cutting wheel and some roloc sanding pads.
Part of doing a job like this is knowing where to make the joint not just how. On this door it only had pin holes along the lower edge. The inner frame work was also in bad shape. I rolled a new skin that was 8" tall to get up where the roll was less and I could get in with a Dolly to work it out. After getting the good shape in the patch I then cut off the inner and went to making the skin repair leaving inner off the door. To know where I'm at with the compound curve I make a bunch of lay out templates to check zones both vertical and horizontal. After tacking it all up I then file down (not grind) all tacks and if necessary bump it back in shape at each tack. If there is any movement at all it is at the tack, not in the panel. Once I like things I then start welding up the seam working 3/4" welds and finishing each off as I go so I don't get a runaway in the panel. Once at this point you can install the back panels and close up access to working the skin. Tig welding gives you about 10% of the metal finish work that Mig Welding does if your good at it. You still can make a Mess if your not. I guess that's what Body Man in a Can is for. Here's the door back on the Truck. Nothing there that primer won't fix as it should be. The tape is to hold the weather strip to be sure things are right. The door has 1/8" gap on all 3 sides. You can do this too. The Wizzard
P.S. NEVER weld on dirty metal! Both edges should be as Bright and Clean as new metal. Rust and dirt make pin holes and hot spots that turn into waves in the surface. The Wizzard
Amazing! Thanks to all advices. this will help everybody in restoring oure nice old cars and getting them back to live.
This is where I see amateurs failing the most. They just want to get it all welded up then do all the grinding . Bad Idea!! The method @Pist-n-Broke describes works no matter the welding type. The idea being to never let the metal get out of shape even a little bit without immediately bringing it back before moving on. When I set the welding torch down for the last time, there is very little grinding/finishing left to do.
I use the easy grind for all of my body work. I get it from my local auto parts store in the smaller spool size that fits my machine. I don't know the exact brand and yes, it is more expensive then regular mig wire. But... It's still not as malleable to hammer and dolly as a hot gas weld is. But not like hammering and grinding on a brick.
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