How much of a gap to butt weld this patch?

[Mike313]

I've spent a fair amount of time cutting this floorpan patch to fit, and I don't want to screw it up now. I don't want to have the panel expand and buckle because it's too tight of a fit, but at the same time I don't want a big gap around the perimeter that's going to be a nightmare to fill. My welding experience is minimal. Based on what I've read on the samba, I guess I need to work very slowly making a lot of spot welds and cooling often until it is seamless. I'm using a tweco 141 110v mig welder with co2/argon mix and .023 wire.
I just want to improve my chances of success by getting the gap/fit right before I start welding. Any advice?? Thanks in advance!

Mike

[67rustavenger]

Mike313
Is the replacement floor panels the same thickness as the og floor pan (18 gauge)? If so then a gap of .023 would work just fine.
I have those little sheet metal alignment clamps that you get from H. F. They leave a gap of .040. When welding start your puddle on the new metal and work to the older metal. Just work with small tack welds alternating from one side of the repair panel to the other. It'll move around a little. But that's to be expected. Take your time and be patient. It's gonna be a long day of welding and grinding.
If I'm wrong here someone will correct me.
The upside of welding in the repair floor panel is that you will gain lots of welding knowledge on a panel that is normally hidden under carpet and undercoating. So don't sweat it if it's not perfect. That is unless this car is intended to be a con-course show car.
Good luck and post pics of the final results.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[theKbStockpiler]

There are lots of post in this forum on this subject:

Arc in between both pieces, watch as the red glow of the heat spreads out to the size of the bead you would leave if stitch welding and then stop the pulse. If you pay attention to the bead and not the heat zone the arc is making, you will burn through.

I don't see the big difference between pulsing with a gap or doing a little hammer welding myself so I think it is just opinionated. If you can't get behind the panel with a dolly it would be different. For a non cosmetic patch, I doubt it would be noticeable either way.
_________________
My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[kielbasa]

I try to go for a perfect fit, and If there ends up being a few small gaps... no big deal. In your case with those receses, it will help alot with any warpage. But you will always need to hammer on dolly each tack to stretch it back out and relieve the tension from the weld shrinking.


This is usually what I end up with, I loose patience fairly quick so I usually end up with some gap. But you can see some areas are tight and others arent.

_________________
Gotta give my props to:
Wolfsburg Motorsports
Dubbers Toy Box
Jeff's VW Speed and Fab
4inbore.com
Kielbasa Industries

[Mike313]

Thanks guys,
Rustavenger, the new metal is 18ga. Thanks for the help, I'll post some pictures as I go.

[Mike313]

After some time yesterday practicing on scrap pieces and adjusting the machine, I got started this morning tacking the patch in place. Here's what I have so far. I think it's going pretty well so far, but any input or advice is appreciated. Thanks,

Mike

[wcfvw69]

Looks good. A nice tip is to grind down JUST the welds as the spot welds get closer to each other. If you don't do that and try to spot weld on the tops between two other welds, you'll get the dreaded pin holes. By flattening the welds before you weld in between them, you get a better weld and can prevent pin holes.

When you grind, try to ONLY grind the spot weld. If you grind on the panels, you can make them thin and cause pin holes.
_________________
Contact me at [email protected]
Follow me on instagram @sparxwerksllc

Decades of VW and VW parts restoration experience.
The Samba member since 2004.

**Now rebuilding throttle bodies for VW's and Porsche's**
**Restored German Bosch distributors for sale or I can restore yours**
**Restored German Pierburg fuel pumps for sale or I can restore yours**
**Restored Porsche fuel pumps or I can restore yours**
**Restored Porsche distributors or I can restore yours**

[Mike313]

Thanks wcf, that's good advice. I had that issue yesterday practicing on some scrap.
Mike

[theKbStockpiler]

'pin holes'?

Higher end welders have an adjustment of a delay of the power or wire feed ( I can't remember which) that prevents the divot in the weld pool. Most likely caused by arc force if the pool is not enlongated. Lesser expensive machines are non adjustable and you have to live with it. If you increase stickout before the pulse is over it should help but the pulse is not that long so it will be tricky to do.
_________________
My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[Mike313]

I think he was talking about small holes left if you mount a puddle between two closely positioned existing tacks. He's saying that grinding down the existing tacks and then filling that gap will help prevent this.
Mike

[theKbStockpiler]

You don't have to pulse weld in a different area every time. You can do three pulses in a row, built off the last one left. THEN, go to the other side of the work and do the same thing so the heat does not build up on one side and it does not take all day to weld the panel in. If you pulse weld this way ,you don't have to have a lot of spots that are 1 and 1/2 width pulses/tacks. The voltage could also be turned up a little to fill a 1/2 width spot. I don't get pin holes but I'm always building a row of three pulse welds in a row so one deposited weld pool is always overlaping the last one.
_________________
My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[Mike313]

Thanks KB,
I've been paranoid about burning through or warping the panel. When making consecutive tacks like that, should I aim the wire right at the edge of the previous one? Thanks,
Mike

[theKbStockpiler]

I usually overlap the last puddle a little bit. The bigger the gap you have the more you have to overlap the last weld puddle. What you are doing is welding on to a weld which can withstand more heat then just the metal alone can. You can weld a little hotter if you overlap more. I do the first pulse and then wait until it is no longer glowing red ,then I immediately do the next one. I think 3 in a row is safe although I have done 5 or 6 in a row. The smaller the patch the more heat is going to be built up because you can't space them as far apart. If the piece is really small I would not lay down 3 weld pools in a row attached to each other. Once you get the hang of it you can get a bead that looks almost as good as a stitch weld and have varying gaps.
_________________
My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[Mike313]

Thanks alot, I really appreciate the help. I'll give that a shot and let you know how it goes.
Mike

[DWP]

I had more problems warping panels from grinding. What I learned the hard way was to grind off the TOP of the welds with the edge of a cutoff saw. I use a 4 1/2 disk in a angle grinder. After all the welding grind everything with a 40 or 80 grit flap disk. The idea here is to cut fast to avoid heating the panel.


DWP

[Mike313]

Thanks DWP,
I'll try that with my 3" cutoff tool. I have some 36 and 80 grit sanding pads for my little die grinder I can use after that.
Mike

[Mike313]

Well, it's not looking as pretty as I would like, but this is what I have at this point. I had some issues in the battery tray section with blowing through the metal. I'm thinking I didn't cut away enough bad metal in that section, so now I'm trying to figure out how I'm going to deal with that problem.

Mike

[bvd]

Mike, it's looking great in my opinion. Most guys get lazy with floor mans because no one will ever see it or know. As long as it's structurally solid right?

Great job! You're probably going to grind down the welds, but you don't have to go crazy as once the seat is installed, and the carpet is down, no one will be the wiser!

And follow the advise earlier about grinding down JUST the weld. In my novice haste, I sometimes get a little too lazy/aggressive with the angle grinder, and make the surrounding metal, around the weld, thin in the process.

I find the sandpaper flap wheels to work great for grinding down welds, but they do tend to wear out quickly. Traditional "grinding" wheels work too, but you have to be very careful, as you can take off a lot of material very quickly!

Keep up the good work! Post more photos as you go! We love that.
_________________
"I paid 2000 for my MR2 with the back quarters rusted out, 900 for the bug. So rice is more costly than kraut."--doc1369

[theKbStockpiler]

http://www.thesamba.com/vw/forum/viewtopic.php?p=7304114&highlight=#7304114
_________________
My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask.

[Mike313]

Thanks guys. I haven't been online much lately, but here are a couple of pics of what I've done. That lower edge on the kickpanel was probably the most work to get shaped right. I actually got the kickpanel section tacked back into place last night so I'm getting close to cleaning up the entire floor and then I can start on the masterseries silver and black.

Mike