Hot Rods filling in 3/8 holes with mig welder in sheetmetal

I'm a newbie welder trying to fill in some holes I drill while removing some spot welds. I'm using a copper plate on the back. I give the welder some quick taps and build around the edge of the hole. I'm left with pin holes after I grind it down. Any tips?

 

Is the shielding gas flow sufficient and is the metal clean

Sent from my moto g(8) power using The H.A.M.B. mobile app

 

IF this is 16, 18, or 20 gauge steel:
Keep with your copper backing, find some UNPLATED flat washers that are 3/8" O.D., smallest bore possible.
Tack in washer at 4 points, (12, 3, 6, 9 O'clock positions), let it cool, then tack 4 more between. Finally, weld the center hole.
Preferably, use .025 wire...Mind your settings.

 

why quick taps?

 

https://www.bobdrake.com/FordItem.aspx?Item=HR-1580

 

A brass backing plate is generally much better than copper, copper tends to stick to the weld.

 

that is what I found on a video online

 

You may be waiting too long between welds and letting the gas escape, or not doing an initial purge when you first start welding. Usually lack of shielding gas causes porous looking welds. You also may be holding the nozzle too far away or too far to the side. You need the nozzle pretty close so the shielding gas works.

 

Clean as in bright metal on both sides is a Must. Also do some test welds on flat same gauge metal as your patching on till you like the weld, then move to what your working on. I do things a bit different that mentioned above. I use a block of Aluminum and vice grip it on both sides of my hole. This keeps it in place. Next I have my 6" 36 grit grinder close at hand. 3/8" is a push for hole size but I do it a lot with no issue. Now do a Rose pattern and Plug weld the hole shut in one smooth move. While still red pop off the vice clamps and get the grinder going and knock off the fill till things are flat. Move on to next hole. It's that simple, well for me it is. Tap,tap,tap is for pussys and guys that don't have faith in what they are doing. Try it on some scrap first till ya get good. I know I questioned it when I was show this method some 30 years ago and now I don't even think about it.

 

As ekimneirbo says purge the gas. I hold the tip about 3/8" away and around a 70 degree angle so I can see the puddle behind the cup. One constant weld and get off grab the grinder while hot. Hay, I see ya shaking your head. Don't knock it till ya try it.

 

Even using a copper backing plate, just going round the hole in one go with the MIG will cause a lot of weld shrinkage which might be difficult to beat out if there's not much room to get in there with a hammer and dolly.

 

Removing spot welds?
Are you drilling all the way through?

 

This is the floor support and inner rocker I cut out that will get plug welded to a new rocker. I drilled holes and removed the old outer rocker. The manufacture had placed the spot welds high and I drilled too high so that I can't get a metal surface to plug weld. You can see in the yellow there is a void of space in some of the holes.

The green is where I tried to fill the hole.
The red is were I'm going to keep the holes and plug weld
The yellow has a partial space void. I'm planning on filling the holes and then drilling new holes lower so I can plug weld to the new rocker.

What is your advice? Maybe I should not try to fill in the holes and plug weld the holes with space voids?

 

This looks like where I would close all the holes and make new ones where I need them. I got to thinking about my above post and thought I didn't give much specific info. On that note I will say I'd use .023 wire. I would start at the 7 O;Clock point of the hole and go counter clock wise around and then finish in the center. It seems to work best for me and I can see everything including the overlap at the start point into the center fill divot.

 

Perhaps cut out that "holy" piece, weld in a patch, and go from there. Might be the easiest way to go...

 

Ted,

If I understand correctly what the OP means, it is a procedure I have found useful when welding a hole closed. It is easier for me to ‘deposit’ a few tacks around the perimeter than a continuous weld. That often leads to ‘burn away‘ of the edge of the hole. Once a few tacks have closed the hole significantly, then puddling the weld for full closure finishes the job, except for grinding of course.

edit: a 3/8” hole in light gauge sheet metal is a lot to fill with just mig wire. I agree with a prior post that recommends using a small washer for a filler.

Ray

 

That is not going to be pretty no matter how you weld it up. It appears that maybe the back side of your top piece isn't clean. It also appears maybe the holes in the bottom piece are pretty thin at the center that were slightly cut with the drill. You may also have a very thin edge left from the drilled hole on the top piece, and then the two pieces are not tight together.

I see a couple options.
1) Drill or cut the one weld you have and separate the two pieces. Then you need to run your drill through all the holes in the top piece so the edges are all a consistent full thickness, then you need to clean the entire back surface of the front piece. While it is off, you may also want to lay the piece on a hard flat surface and flatten the piece out flat.
Then you need to address the condition of the bottom piece. It may sound dumb, but you need to fill any places that the drill may have skinned thin. Start by cleaning both sides of the metal to shiny clean, then make sure the piece is flat. Then you need to fill any debits and sand the top surface clean and flat again. Then you can clamp both pieces together tight and do your plug weld in what ever method works best for you. I suspect when everything is clean, flat, and fits tightly together, it will plug weld much better.

2) Keeping everything as it is, then use a flat bar on the back side and a hammer on the front side and tap both pieces together tight. Weld it as best you can, grind smooth, then go back in and weld up any problem areas and grind smooth again. Repeat as often as needed until you get the results you are looking for. Gene

 

serious clean is an absolute, obviously a good ground on your circuit also(goes without saying, but gets overlooked). When firing off to deliver wire to the point your filling strive to be smooth in your gun control, if your prep is good and your technique is nailed down those little holes should fill in one pass with no real problem. As has been said, these are the absolutes in this kind of thing, additional helps are all well and good as long as the basic principles are understood and a level of mastery is achieved. Wow!....all that being said, roll down yer' sleeves and fill some holes...

 

One thing, no matter how well you do it, MIG welds are somewhat porous (tiny) so dont be discouraged about some holes. Its the way it goes.
But depending what youre filling, youd be better off with doing a patch piece than trying to fill it all with weld, that makes a lot of heat/warp

 

Old Chevy, I've read near all the above posted advice. What is clear is that there is more that one way to get things done, none of them are wrong just some better advice than other. What I notice is constant here is things must be clean and your parts are not clean enough. I believe your next biggest issue is that your New to this kind of work and trying to get a Home Run your first time at bat. That's all well and fine but not very likely. Practice my friend practice and not on a must have part. Find some drop tin and start by duplicating what you have made out of your must have pieces and get good at fixing it, then move back to your Rocker repair. One thing I disagree with is porous Mig welds, or porosity. I do see it often in novice welds. There are a few things that cause that but all can and should be avoided. Having a good Mig machine don't automatically make you a good welder and what your trying to do is a tough job at best. Keep trying, you'll get there.

 

What you are doing, several small tacks to make the hole somewhat smaller and then a final burst to close the hole works well for me. Smaller holes can usually be done in one or two short bursts. So there isn't anything wrong with that part of your technique. When doing sheetmetal I found that .030 wire was often problematic but I could get it to work. Just had to fill some additional enlargement of the holes ocassionally. I found that using .023 wire actually gave me some control. Since I'm too lazy to switch the wire,liner,tip and roller, I purchased a separate welder and just sat it up for .023 all the time. If you aren't using .023 and you switch over, be sure to change the liner. With .023, the wire is so thin that it needs the support or it will kink and nest. You can usually get by with using .030 wire in an .035 liner, but the .023 is very unforgiving when you use an .030/.035 liner. What you might consider is sliding a thin backing strip in behind the all those holes.....if you can get the burrs off the backs of them.
I don't think anyone has asked, but what type of welder are you using? Cheap welders are often the source of many problems. Also, for what you are doing, a little porousity isn't a problem. If it looks really bad, its usually a lack of gas shielding. I had that problem once and I have a very good welder. I changed regulators, tried another tank, changed my wire, tried different settings......nothing helped.Finally I took it to the repair shop. They had it fixed in 10 minutes. Turns out that I had stepped on the cable for the gun and it had pulled it slightly out of the welder.It was still in the welder but had moved just enough to let one of the Orings leak. So I wasn't getting much gas thru the nozzle. Pushed it back in place and magically all my problems went away. Troubleshooting can be frustrating............

 

Checked the Bob Drake link, but it doesn't say what thickness those are.
16 ga perhaps ?

 

Two most common contributors to porosity, Rust being it burns and takes away your shielding gas and any coating on new metal being it also burns. In other words as ekimneirbo mentioned, the Lack of Shielding Gas. You could have perfect metal conditions and have a draft come through your work space and cause the same issue.

 

Maybe I'm missing something here. Are we talking about filling a hole with nothing backing up the backside? I realize it takes a lot more skill but is there some reason for not having a piece of metal to weld to on the back side? Can somebody explain?

Here's what I did to weld up holes in my trunk lid

https://49fordcoupe.smugmug.com/Tips-and-Tricks/i-PGtDMG6/A

 

.060

 

where did you find that ?

 

I have 3 boxes and used my digital calipers.

 

ah, OK thanks

 

I second the advice of above.........what's thee big deal with porosity when filling holes?! Dab some body filler/hi build primer and move on.
Now......if it was a structural issue that's a different story. (like steering/suspension/frame) Solid weld (no pin holes) is needed for maximum strength. But cosmetic is no huge deal....because its gonna get covered with paint etc.
6sally6

 

Clean the copper back plate each time each hole I have best results the tip straight up over the hole and a bit close to keep the gas in the weld AND as every one says clean metal and practice you will get it done