How to patch panel

[jakekk05]

I am wondering what is the up to date way to patch panel? What ive been doing is putting the patch behind all of the good metal on the car then pop riveting the patch to the body. The problem I run into is trying to counter sink the pop rivets. does anyone know the proper way to counter sink the pop rivets or even a better way to patch panel?

[TheSilentChamber]

Get rid of the rivits. Cut out the bad area and weld in a good piece. You'll need a MIG welder, know how to use it. Spot weld it about 4-6" appart and work your way around so you dont build up heat.

[mike@af]

Just what TSC said. MIG weld it...and by MIG weld I mean MIG weld, not flux core. Flux core is crap, and definately not suitable for sheet.

What gauge steel are you using?

[jakekk05]

Im using scrap metal from a hatch civic fender. I have a MIG welder and i tried using it but i just cant get it to work right. Whats the tank on the welder suppose to be set to? so I should cut out the rust then take the scrap metal and place it behind the hole then spot weld around the edges?

[TheSilentChamber]

20psi, and yes.

[mike@af]

Originally Posted by jakekk05

Im using scrap metal from a hatch civic fender. I have a MIG welder and i tried using it but i just cant get it to work right. Whats the tank on the welder suppose to be set to? so I should cut out the rust then take the scrap metal and place it behind the hole then spot weld around the edges?

What position are you welding in? Flat, horizontal, Vertical or overhead? For flat set the regulator at 15-20CFH. For horizontal and vertical set the regulator at about 25CFH. Overhead which I doubt you are doing, so I wont get into that.

Depends how big the hole is. If its a big patch it needs to be flush with the rest of the body, if it were behind it would create a relief, if above it would create a ridge. If its a small (no bigger than 1.5") then place behind the hole and weld and finish it well.

What wire are you using? Make sure you are using .023 to .030 ER70S0-6 MIG wire with a .024-.030 Contact tip.

[jakekk05]

You say it needs to be flush when its a big hole. Is this the right way to do it ?>>>>> http://www.autobodystore.com/patch.htm

[TheSilentChamber]

Thats one way of doing it, I allways use magnets witch eliminate that step and makes the surface flush if your using slightly differnt thickness metal.

[jakekk05]

How would you use magnets to skip that process? I appreciate the help!

[TheSilentChamber]

Go buy you some welding magnets, stick the patch in place, stick the magnet where part of it is on the good panel and part of it is on the patch, put a few of them on it depending on size of the patch, tack it in a few spots and you can take them off.

[jakekk05]

That makes sense,the only problem i can see i will probably have is either having a small gap between the patch and the car body so the weld shoots right through. Or ill weld it on but then when i go to grind it down, ill grind all the weld off and it'll fall off. What should i do to prevent these problems?

[TheSilentChamber]

Cut it slightly bigger then slowly remove more material so that you have 1/16th gap all the way around. If it falls off your getting no penetration- learn how to weld.

[mike@af]

Originally Posted by jakekk05

That makes sense,the only problem i can see i will probably have is either having a small gap between the patch and the car body so the weld shoots right through. Or ill weld it on but then when i go to grind it down, ill grind all the weld off and it'll fall off. What should i do to prevent these problems?

I am going to sort of repeat what TSC said, just more in depth.

In welding fitment is key. If you do not fit it well, then you are not going to have a good weld. The gap between the fit should be no larger than the wire you are using. Which should be .030 or smaller. 1/16" is alright, but the wire can go through which creates a bad, and messy weld. There will also be a lot more finish work. Also MIG welding shrinks the metal. That will cause the gap to enlarge, and then you will be filling instead of welding. I will also mention something else on the shrinking later.

If you grind the weld down, and it falls apart then you are not getting correct penetration. And just like TSC said, you need to learn how to weld. Welding 19Gage or thinner you should see a light bead on the back of the panel. The problem with MIG is that its easy to make a nice looking weld. The problem with a nice looking weld is that its often decieving. Not all pretty welds are good welds. Only experience will tell you if its a good weld.

Back to the shrinking now. Since the area shrinks when you weld it the area will then need to be stretched again. It does not shrink much, but tension should be relieved. The way to do this is to hammer and dolley in the HAZ. Do this before grinding down the welds.

Hope that helps.

[jveik]

i replaced the cab corners on my 73 chevy truck and what i did is i took a pencil and traced around the patch on the body then cut near the line and then finely grinded bit by bit until i had a perfect butt joint then i just tacked it up with my mig welder. make sure you use narrower wire and set the welder to only the first or second setting with a wire speed of about 35ish (dont know the units tho lol). just tack like they all sed every few inches and make sure you can either paint the inner side of it afterward or paint it as good as you can before welding it shut. it will burn some of the paint but at least most of it will be rust proof.

i used fiberglass reinforced bondo to fill between the tacks cause im lazy but im sure if you were really careful you could weld along the butt jount without melting a hole out of it.

also, for painting the rear side, i would highly recommend using "Por-15" it is sold online and is VERY expensive but is litterally INDESTRUCTIBLE. you have to try a couple of times to finally scratch all the way thru it with a key or a screwdriver before you finally get thru. its freaking CRAZY STUFF!!!!!!

[jveik]

by the way, use water to shrink the metal after welding it. it makes the welds brittle, but if its just a body panel that wont need to take weight or anything then it doesn't matter. it will shrink up very nicely