Pinholes

Swamp Donkey · March 18, 2021, 10:32:15 PM

I'm trying the welding thing. And I'm ending up with a few pinholes every now and then. I've watched many hours of YouTube trying to learn how to weld sheet metal. Still having issues. I'm using a Miller 252 with .6mm wire or .023 about 15 CFH amp 16.3 wire speed around 220.

I've practiced for hours on scrap sheet metal and seem to do ok on my practice stuff, but come showtime I am not coming through. Haha.

My question is, with these pinholes, do you guys just keep filling them in? I do have a small piece of copper that I use as backing sometimes for filling in bolt holes. Or is there some other technique or trick I could try.

RUNCHARGER · March 19, 2021, 07:10:51 AM

Keep filling them in. Shine a light from the backside after grinding too, it will help you find any holes. It's a fine line between getting good penetration and burning through. Welding sheetmetal sucks actually, you don't run a bead you just keep spot welding over and over and over. The copper backer helps if you can get in with it.
Sometimes it's hard to hit the center of the two pieces as well and that's something you have to see right away if it's happening before you get too far. Also if you're practicing on scrap OEM metal I find it burns through less easily than the Taiwan metal does.

anlauto · March 19, 2021, 07:17:34 AM

..and the more you grind, the thinner the metal gets...

DeathProofCuda · March 19, 2021, 02:04:49 PM

I'm in a similar situation, although I am still in practice mode and haven't welded anything on the car other than an O2 sensor bung. It's still pretty hit or miss for me trying to bridge a gap without burning through if I'm not using a copper backer. This is my most recent practice piece, which is an old 90s vintage trunk extension that I'm not planning to use. This has been a pretty good practice exercise for me for learning that fitting patch panels takes more time and effort than you might think after watching some YouTube welding videos.

edison1970 · March 19, 2021, 02:23:53 PM

Looks pretty good. Just turn the heat down a little to fill the holes.

torredcuda · March 19, 2021, 02:46:10 PM

Turn up wire speed just a bit or just quick zaps to fill in pinholes/voids. I usually weld, grind and do a second weld pass to fill in any areas that need it, first pass of filler use Marglass, All Metl or a similar "waterproof" type as regular plastic filler will absorb moisture thru any pinholes and bubble up down the road.

jimynick · March 19, 2021, 07:05:10 PM

Quote from: torredcuda on March 19, 2021, 02:46:10 PM
Turn up wire speed just a bit or just quick zaps to fill in pinholes/voids. I usually weld, grind and do a second weld pass to fill in any areas that need it, first pass of filler use Marglass, All Metl or a similar "waterproof" type as regular plastic filler will absorb moisture thru any pinholes and bubble up down the road.

Yep, what the man said. That's damn good advice all ways around.

Marty · March 19, 2021, 08:40:26 PM

Cuda Cody · March 19, 2021, 08:40:40 PM

Try to think about where you point your heat when welding. Think about it like you're shooting a real gun. Where is the gun pointed? If you point your heat (like a real gun) at the thin area it will be more likely to blow through and create a pin hole or blow out. But if you point it towards a thicker area (like the one of the previous stitch weld areas) it will stop the heat and build up material easier.

Also, do not pull a mig welder tip area from the weld for a couple seconds. That will keep the gas area there longer and keep from pulling impurities in to the weld.

dodj · March 20, 2021, 04:54:16 AM

I found getting the original metal EXTREMELY clean made a huge difference to my mig welding results. Also getting a good ground with the clamp.

MoparLeo · March 20, 2021, 11:18:11 AM

Just keep practicing. Some skills take longer to master than others. When it gets too hot just stop and let it cool down. If the gap gets too large you can just use a piece of extra wire to use as a bridge to fill the gap. When you go to tack this in, it will melt into the gap.

7E-Bodies · March 20, 2021, 12:24:45 PM

I had the same issues on another car I built, a 73 Cuda that was like a screen door in places. I kept fighting blow thru's until I began momentary arcs, each striking the last bead that laid down instead of the original steel. (I guess imagine overlapping pennies in a line). This allowed the weld to flow over the next pinhole instead of pushing wire into that hole. Also I would time my arcs roughly a second apart so the last one still was glowing but not molten. I'd also maintain a lower than normal wire speed on low heat. I hope this ramble makes sense. Another thing I stumbled across was my Miller had a polarity setting. Upon looking through the manual (I do that on rare occasion), I saw where I had polarity reversed. After 35 years in the electrical world, I'm at a loss for words as to how the hell that'd make a difference, but either it did or I got better at it right at that point. Just another hint. Also, your copper idea is magic. I use that too as long as there's a way to secure it flat to the other side (also known as RARE). I have quite the collection of copper plating for that very reason.

DeathProofCuda · March 20, 2021, 01:07:14 PM

Quote from: 7E-Bodies on March 20, 2021, 12:24:45 PM
Also, your copper idea is magic. I use that too as long as there's a way to secure it flat to the other side (also known as RARE).

Yeah, that's what I figured, which is why I've been trying to practice without it. Have thought about picking up one of those magnetic copper backer gadgets that Eastwood and others are so proud of. Anybody tried one of these and like it?

https://www.summitracing.com/parts/sum-900901?seid=srese1&gclid=Cj0KCQjwutaCBhDfARIsAJHWnHu29tdes_tp1FcaV4EI69dFRljtDFWt2iHM7ggYMezJR53MamqGzREaAsuNEALw_wcB

I saw a post on one of the hot rod or jalopy forums where a guy made something similar for a few bucks with copper plumbing pipe caps and a few bucks worth of other hardware.

BTW, @7E-Bodies, did you ever figure out the trick to get really consistent looking plug welds?

7E-Bodies · March 20, 2021, 02:09:41 PM

@DeathProofCuda just when my plug welds start looking good, I drop one through the tongue of my boot. Horizontal vs flat vs what I had for my last meal, lol. I basically set up practice pieces from old panels and nail down my settings then do the circular motion thing. Also, I've had welds go nuts when a magnet was nearby. Not sure how the Eastwood magnet would work.

Rbob · March 20, 2021, 06:00:14 PM

My 2c.

Most important is good ground, as far as wire speed I use a piece of scrap metal and set the mig gun at an angle with the nozzle touching. With one hand on the wire speed knob and the other on the mig gun pull the trigger and leave it pulled while you turn up the wire feed until it sounds like frying eggs. If you turn it up past it will start to push back and make popping sound, if wire speed is too slow it still makes a type of popping sound but the wire actually burns off and starts welding once contact is made or the wire burns back into the tip and gets stuck.

Butt welds? best if you can get copper behind it, flatted out some copper pipe (just the last 3-4 inches of a 12" piece works, 1-1/2" cap or whatever. You will be amazed, used stitch type weld like 1 second on, 1 second off. Some welders even have a stitch mode.

Plug welds? make sure they are tight with no gaps, a little taps with a bodymans hammer to close the gap before you pull the trigger. Make a small circle motion and complete the weld in one motion. Practice helps.

You do not want a wide blue line (heat transfer).