Pan Replacement: Plug Welding Tips and Tricks

[ernieballbass]

hey guys,

so i'm having a little bit of difficulty with my plug welds. i drilled 1/4in holes on the new floor section around the edge where it connects with the tunnel. i thought it was fine until the whole section popped off after i was "finished". i obviously wasnt getting proper penetration in the weld.

no biggie, i redrilled the holes, grinded old welds down, and tried again and cranked up the heat.

i must have warped the crap out of the new pan because i had to force them down to meet the pan....well, my plugs welds still didn't hold...even with amps cranked up, i'm still not getting enough heat to penetrate the bottom panel.

so i am here now reading/asking for any tips and tricks. i ordered another pan and i definitely don't want to screw this up again...

here is what i'm working with:
- Hobart Handler 140
- 75% argon mix
- .025 wire
- and wired wheeled tunnel lip to shiny metal
- ground is good too
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What I lack in brains, I make up for with good intentions.

[57BLITZ]

After fitting the pan halves. I used a pneumatic hole punch from HF Tools for the holes. That tool is worth its weight in gold!
I then put the pans on the chassis and marked the backbone tunnel flange through every pan hole, I then removed the pans and drilled into the flange with a sharp 1/4" drill bit to a depth of about through the first layer of the flange. Those holes in the flange allowed some heat to build up before the puddle reached the thin sheet metal pan. Just keep your wire in the center of the hole without moving the gun 'till the hole fills and the puddle melts the edge of the hole in the pan! You MUST keep the pan down tight to the flange before you start to weld!!!! Leave a gap of about 1/8' along the edges . . . it will probably pull in as you go.
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Jesucristo es mi Señor y Salvador!

[ernieballbass]

[eyetzr]

use small screws to hold it down & together. Drill out for your plug welds. Drill small 1/8" hole for hold down screw. every 3 or 4 put in a screw or until you are happy. weld spot, remove screw weld spot. You get the idea. There is a small screw I use called a Tek screw. Drills its own hole, as it threads in.
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I think he meant "rare", as in "not well-done"

[Danpa]

This is what I did to hold the pan surfaces tight together;

Leaned on the end of the 2 x 4 "lever" with my chest while I welded. works really well.

Dan

[Northof49]

I would increase the size of the hole. The metal flange you are welding it to is much thicker than the pan, and needs more heat input to gain fusion. Heat takes time, and a larger hole will give you more time in the centre of the hole to allow it to heat up before you move the arc to the edges.
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1958 Karmann Ghia owner

[marklaken]

I took some cheap harbor freight vice grip clamps and welded pieces of scrap 1"x1" square tube to both of the c-clamp arms so that I could reach the plug weld tabs with the modified c-clamp - they were cumbersome, but they worked well - it's not like you need alot of clamping force, just enough to hold the sheet metal together.
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[theKbStockpiler]

I built this c clamp because I was tired of fooling with rivets and sheet metal screws. It saved a lot of time on my last project. It's heavy ,needs to be supported and not that strong because it is not made from tool steel

Northof49's advice x2 . If you let the puddle engulf the top piece without moving it , the weld will be weak.
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Use all safety devices including a mask.

[modok]

1/4 size hole should be ok, but 5/16 might be good too. Why do plug welds anyhow?? replicating the stock look I assume.
Don't start in the center of the hole, start at the edge to an eight out, and then work your way to the middle, then stay in the middle and just go round slightly concentrating the heat in there and let the metal/puddle build up and touch the edges of the hole and fill in. it's tough to get enough heat in the lower piece without melting the top piece, but it's what I aim for.
THe first one or two seconds of a mig weld are too cold and have no strength, so you don't start in the middle! Unless you have a more powerful machine and turn it up to where it is hot enough you'll burn through in 2-3 seconds, then ok start in the middle.

The small wire isn't best but it's ok, keep the wire speed on the low side and power on 3 or 4 (max)

If you are short on power due to poor wiring/extention cord then put in a spool of flux core, can turn on the gas too to see what your doing.
Flux core will actually penetrate better for a plug weld, tho it's terrible for most everything else on a VW.

[NewTechnicIan]

KbStockpiler, if it's worth doing it's worth OVERdoing, right? That thing is awesome!

But I agree with Modok, I drill 3/8" holes so that the arc doesn't accidentally just catch the top piece, I start on the bottom piece and get that sucker warm before I guide the puddle over to an edge. When the metal gets thin near the tunnel on the floor pan, I generally let the weld cool a bit so it doesn't just melt that side of the hole, then start in the center again and guide the pool towards the edge, not directly on to it.

Hope that helps!
Ian
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My 73 Standard build - It's painted! It drives under its own power! Time to get it wired and upholstered!

My 1679 Engine build.

[raygreenwood]

Another simpler way is to use a propane torch on a, stand to beat from the backside. The metal on the bottom only needs to be about 500 degrees so that it does not become a heat sink for the puddle. Then you can keep the power low enough not to blow the edges away on the top layer.
Ray

[ekacpuc]

You can weld a tab on the tunnel and stick a wedge under it to push the pan down too. Just run the tab (maybe 3" long, can be as long as you want) vertical above where you wanna fit. You weld one side of the tab (the side you're gonna push wedge into) the part closest to the wedge about 1" long will do. That way you can just hammer the side not welded to break it off, grind the tack and move on. Called a dog and a wedge.

Also for the spots that are close but not quite touching you can hot tack. Just run a tack and give it a lil smack with a hammer. The tack will cool
as you smack it and hold it tight. Doesn't work with large gaps.


Run bigger plug welds, 1/4" is too small. Since you're welding thin metal to thick you can turn the heat up a little more than normal (more volts and wire speed).

Make sure your polarity is correct. Should be electrode positive.

[Dr OnHolliday]

Clickos (klickos?) Work great to hold sheetmetal together. Came from aircraft industry but even HF sells them now.
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[Mike Fisher]

cleko
https://www.google.com/search?q=cleko&ie=utf-8...channel=sb
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[eyetzr]

Clecos will help, pricey little things, if you plan to do more of these projects. Clamp looks good.
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I think he meant "rare", as in "not well-done"

[MURZI]

Way over thinking this. I drill the holes and then shove a small sheet metal screw in every other hole. Weld the open holes and then remove sheet metal screws and weld/fill those holes. Easy.
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[ernieballbass]

well, i ended up making these a couple of weeks ago. i'll try to weld in the floor sometime this weekend. wish me luck!

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What I lack in brains, I make up for with good intentions.

[eyetzr]

you may find with your modified 'vice' grips are the flex that will happen when you clamp down on them. I did the same for a fibreglass truck hood I was repairing. They would twist & flex as I was clamping things together. The "engineer" beside me said that the clamping force will be divided as the grip extends. Screws are the simple way to go. As somebody posted earlier, screw it together, weld hole, remove screw, weld hole, rinse repeat.
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I think he meant "rare", as in "not well-done"