Tiny pinholes in sheetmetal welds
 

Hi, I've been a lurker on here from time to time, but now I have a question. I'm working on a '68 Charger doing rust repairs. The following pictures are of the trunk gutter. The tail panel has been removed.

The problem that concerns me most at the moment are these small pinholes I get in my welds from time to time and why they are happening, how they can be prevented, and how to address the current ones for epoxy and paint. Most are not completely through the material. The pin in the last pic is a small T-pin I use mostly for probing electrical connectors and is there for size reference.

I will include pictures of the whole process of the patch replacement as I do not know where my mistake is at. I'm using a Hobart 140 MIG with 75/25 gas set at 20 CFH with the trigger pulled, .023" wire, and I ground down the tip of the gun nozzle even with the contact tip, so I could see a bit better. I use tacks the whole process and planish them ASAP then cool them with my air gun for a few seconds.

The replacement patch was made from 20ga sheet steel. Machine settings were 2/30-35. I do not move the gun at all when tacking, just hold it perpendicular to the surface, aimed at the gap. I don't always trim the wire after a weld, but sometimes I will.

Any questions, just ask. Any help is appreciated. Thanks.

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I think I would turn the heat & wire speed down a little. Try trimming the wire before each tack and see if it helps. It don't look like undercut, what is happening is the welds are "sinking". This is why I suggest turning the heat down. It looks like some welds are wanting to fall out due to heat, creating a crater.

Welcome SRT. :welcome: I too use a Hobart Handler and like it a lot. I do set my flow meter to 30 cfm. I find I get a little cleaner weld with the higher setting. How about taking some scrap metal and set your flow meter higher then work your way down and see at what point it begins to deteriorate. When you trim the wire you allow the purge gas to displace the oxygen before the arc is struck also. One last thought. How clean is the bottom side of the metal. Could you be getting some contamination from the underside of the panel.

John L

I'll play with the wire speed on some scraps. I've tried with the heat setting on 1 and there just doesn't seem to be adequate penetration with this 20ga. Sometimes I will do two tacks one right after the other when dealing with a longer gap, so maybe that is putting too much heat into it like you mention. I'll start trimming the wire before each tack as well.


I will turn up the gas flow and see how that works. I used to keep the gas at 17-18 CFH with the trigger pulled but upped it to 20 in an attempt to get rid of these pinholes. I've heard of too much gas flow causing turbulence and causing problems as well though, so I didn't go up much with it. That's a good point about trimming the wire so it doesn't obstruct the gas flow. I clean both the top and bottom sides with a clean and strip roloc disc before any welding and after each round of tacks I clean both sides with a wire brush.

Any suggestions on how to treat the current pinholes in preparation for epoxy and paint? Should I drill them out and weld up the holes? Will the epoxy be sufficient to fill these in? Or should I put a skim coat of filler over them after epoxy? I'm new to the paint and bodywork side of cars.

just throw some kitty hair in them or just tack them shut. you're a damn good welder btw.

If you can, back up the area welded with a piece of copper.

Even a piece of copper pipe flattened will be a huge help.

Yep, I do the same thing

You can just go over the spots with the welder backed with the copper piece.

Or you can just fill the pin holes with fiberglass. I did that with my old car back in vocational class when I had the same issue as you and it came out fine.

What did you use to grind the weld? It looks really neat.

Looks to be a crater in the center of some of your spot welds.

If so, You need either to turn up the wire speed a bit or hold the trigger for a moment longer to fill the crater that forms in the center of the puddle.

Can't see, put a cheater lens in your helmet, makes a world of difference for old eyes. It makes things brighter for my old eyes. Another trick Shine told me was to put a spot lamp shining on the weld zone, and it does help.

I never heard of a cheater lens..zI'll be looking into one of those. Its amazing all the tips one can learn from all the others here..35yrsat it and still learning something new every day, theres not many jobs like that....

The work you are doing is absolutely TOP KNOTCH! Very nice work, my question is if these holes are going thru? If they are simply craters you are so close to PERFECTION it isn't funny. If that is the case, simply epoxy prime the area and what the epoxy doesn't fill fill with polyester putty. We are talking VERY minor stuff here, if they are simply a tiny pit.

If they are going thru, or if you simply want to move to another step in your journey to absolute perfection, well that is another story and you need to work on the welding using the tips the others have already told you.

If they are only a tiny pit you simply need to perfect your welding with the tips given. A little more of an overlap between welds may do it. I personally find that I weld much hotter then others to get this done. The first spots, keep the wire speed and heat down. Once those are done I turn up the heat and wire speed because I have the nice thick metal (the previous welds) to weld to and I want to be able to weld into those welds with a little more authority. But just practice with the tips given on some scrap. You are a cat hair away from doing flawless work, you have true talent and passion. And nothing can overcome like passion, nothing!

Cutting the wire off and purging the gas right before you weld is a good tip if you are looking for perfection. The gas is a "shielding" gas, it pushes away air borne contaminates. If you just do that then the nozzle is full of gas and when you hit the trigger it's right there for you. Cutting the wire, that is a very important step. The little ball of wire at the end is actually "oxidized" it is technically "rust"! You are pushing in a glob of rust when you weld, think about that!

But honestly, you are doing the kind of work that I would be thrilled to have every time. As a pro I have learned what I can get away with, you haven't. :) Because of this you are doing the kind of near flawless work that I would often skip, and simply make up for the flaws with a little filler and get on with life. Why, because I know what I can get away with.

Many, MANY pros who do this every day wouldn't or couldn't even get close to the quality you did there.

Taking the time to do the beautiful work you are doing has eluded me often. I can't wait to get back to doing some restoration work (my own car) so I can have fun with it like you are. Doing regular old collision work every day you loose some of your passion, YOU have some passion that is for sure.

Let me make this perfectly clear, that work you are doing is absolutely BEAUTIFUL and you have NOTHING to even think about IF those are just little divots in the metal which I think they are from what I can see in the photos.

Really, BEAUTIFUL work there! :thumbup:

Brian

I absolutely agree with Brian 100% ...Well put...

Welcome to hotrodders.com, another Charger owner. When I was looking at pics I've immediately recognized Charger tail panel.
Are you a member on d-c.com yet?
As far as welding you're trying to be perfectionist. If those holes are not all the way through some spot putty would fill those in, or you can epoxy prime it and then 2K high build will cover imperfections like these.

Look at this photo and you will see that your first welds are looking great, they have been ground down and really looking great. The second welds look like they were done at the same low heat setting and they didn't penetrate nearly as much as they should have. If you had the wire speed up a little (it is carrying the electrons, look at upping the speed as using a larger water hose) and the heat a little (look at the heat as the pressure behind the water in the hose) so you can make a faster, hotter weld that will flow more quickly into those first welds. It will provide a flatter weld, as the wire is going INTO that surrounding metal and not sitting on top.

But even the first welds could us a little more wire speed as you can see there is that divot in the middle where it didn't get all filled up before it solidified it collapsed.

We are talking just tiny adjustments. Do a long practice weld and mark it off with a Sharpie pen. Use a particular setting, weld a few inches, change the setting and weld a few inches more. Now, you want to skip around so this would be hard while you are changing settings but not impossible. You could also weld a few at one setting then work on something on the car then go back and put at little more at that setting before you move onto another setting.

One very important thing with any kind of practice, you need to do EVERYTHING exactly as you would on the real thing. Practicing basket ball with a ball that is low on pressure isn't going to help you a damn bit in the real game when the ball is harder. You need to do everything exactly the same including that fine prep you did. One more thing, if you get the gaps tighter you are better off as well. Lay your piece of metal on the area you are replacing and using a scribe, a sharp awl or scribe and mark the metal up tight with the new piece. Trim the old junk off right at that line and your new piece is going to fit tighter.

Brian

yep. it would be nice to be able to do multiple passes with welds but I'm simply not allowed the time to do so. It's weld once, grind, and live with it. Some guys on my youtube channel ask about that stuff and I tell them What boss is gonna allow me to spend all day on something so it looks good when it gets covered up in the end? in reality I envy guys who can spend the time to do it absolutely right. It's just that most jobs don't allow it so you have to learn how to keep integrity in your work AND get it done in a reasonable amount of time.