I will never butt weld sheet metal again

Yep! Happens all the time.

 

I am learning butt welding on panels by necessity. Lap joints on a 50 chevy pickup box would look like $h!t. Its coming along, patience is needed.

 

I realize this might part of my problem. I have a Lincoln 250 MIG welder. I've always ran .035 wire, I know way too big for body work but I've been doing OK all these years with it. Well, since I was going to butt weld I bought a spool of .024 but didn't have a drive wheel for that small of wire so I bought one. Started using the .024 wire and it worked like crap. I talked to the welding store and the counter guys told me my welder doesn't work good at the lower voltage range. They suggested I try .030 wire which I have in the machine now. It's a bit hard to work with but that's not my real problem. It's the small pin holes. I'll try what was suggested, spot weld and then try to stitch weld when I get them maybe 1/4-1/2 in apart.

HRP don't get too worked up. Not everyone has the tolerance to work with the inexperienced or ignorant. Ignorance isn't necessarily a bad thing, it just means we don't know everything and must ask for advise for things we don't know. I guess there are some who know the answers to everything.

 

The heat should be set to provide a full penetration weld. Then the wire feed should be set to prevent your blowout.


Bob, I typically weld sheet metal at the next higher settings from what the machine calls for and do any tweaks from there. For example, The machine's suggested settings for sheetmetal (or otherwise) are based upon a full weld pass. But on sheetmetal, if you were to inspect the weld afterward, the start of the weld would be cold, another inch along and it would be about right, and another inch along (if you kept the weld going) once the heat starts to build up it would be borderline of blowing out the weld. For this reason, most people using a Mig on auto sheet metal will weld one tack at a time, or what I refer to as "dot welding". So since this is done with a short "zap", it needs more heat to provide a full penetration weld with the one dot we just welded. Since there is more heat than the metal requires, there may be a tendency to blow a hole. But before backing off the heat, try increasing the wire feed first. Think of it this way, if you are applying enough heat to perform the weld but not enough wire filler that said heat is looking for, then it will burn away at the surrounding panel, hence the blowout. You want the happy medium that has the heat needed for full penetration weld and enough wire speed that it doesn't blow holes, all in welding one dot. Here's a sample, front and back sides showing the full penetration welds on a Fairlane trunk opening repair...





This was close enough to the adjacent bend detail that it held most of the weld shrinking issues in check, so I waited until after all welding complete to planish the welds...but typically for something in the middle of a flat or low crown area, you would want to planish each weld dot after the weld, then grind it down to just above panel surface so it will be out of the way for planishing the next set. Next, I would suggest overlapping the last weld dot, instead of welding a dot in the center of the last two. By overlapping, you will eliminate those pin holes you describe, and when trimming/fitting up your panels, make sure they are butted tight together.

The settings on my machine will likely not apply to what you have. So if you are performing similar methods in your welding, I would recommend following your machine's recommendations for 16 ga metal (if welding 19 or 18 ga panels) and do some test welds. If you don't get full weld penetration in the one dot, then go the next higher heat. If it's blowing holes, more wire feed speed. I will add that where most use .023 or .030 wire on sheet metal, but for whatever reason my machine and the setup I'm using seem to do better with .035 wire. But as pricey as wire is, I would say to try adjustment changes first (cheaper) before allowing anyone to talk you into changing wire size because it's what they are using in a different machine... That's the method to my madness, hope it helps.

 

My only point was that lap welding traps moisture, causes rust and makes metal finishing or body working the seam difficult. It's true, theres nothing to debate.

 

7 ft butt weld on my torino. Longest one i've done to date. Was a good spot to do it thou. Did the inners as well.
Is this a pissing contest now?

 

I teach my young guys BUTT welding it is a must in my shop then we metal finish the seam to be undetectable! It is tricky and does take practice, but the results are well worth the effort especially in high end restorations. When I was a kid lapwelding was what we did then hammer the spot around a bit and filler up with mud, but as you get further along you want to get better each time, now I find myself upset if I have to use more than a light skim coat! Lap welding takes me twice as long plus more time with mud work, plus unsightly from the inside, and you always have that rust issue to deal with! Remember water always wins that means humidity as well, you lap weld and have a small space and moisture finds your filler from the back side, LOOK out it is gona soak it up like a sponge! and it's doomed to fail!
Butt welding tight fit panels is the way to go, low heat, spaced out tack welds, a cold wet towel, or air blow gun to cool weld area quickly, Now I'll go in and hot seam weld 3/4 inch at a time, jumping back and forth from all the areas. Yes it will warp a little can't get away from that, the metal pulls to the heat. You need to try pulling you welds out of the pool of metal fast and close! at a 33 degree angle, you will get a blow through now and then, and that's not all bad, let you know your getting good penetration, don't give up practice and you'll be doing the same work as laping but in a 1/3 the time! Sign up for my weekend work shop Feb 23 & 24th of Feb. We are chopping and lots of sheetmetal work on a 47 I-H truck cab 8 guys last month had lots of fun and learned a lot of welding & dressing!

 

MP&C, the last part got my attention. I was originally using .035 wire, just for putting a few spot welds in but then changed to .030 because I figured I should use a smaller wire. I've always used .035 wire for sheet metal and I'd get the occational blow through but I didn't have much problems with it. I've done butt welds before like when joining pieces togehter to form a box. It got late tonight. I've been working on this car all day and maybe that's a big contributing factor also. I'll start fresh tomorrow and see how it all works out.

Job looks great.

I hope this doesn't turn into a pissing contest. I was just letting off some steam and have gotten a lot of good advice. Hate to see it degrade, maybe someone other than myself will learn something.

 

Put down the MIG and pick up the torch. Yes it takes practice, but you'll never want to mig sheet metal again.

 

For sure, When you don't give a shit about QUALITY metal work.

 

Hot rods by Maaco.

 

Bob, I've got a roll of .023 here and took it back out. I've had better luck with the .035. I would say that when it does run out, try some ER70S-7, it seems to lay a little flatter and is a bit softer, for easier planishing and grinding. Compare my 65 Fairlane weld dots to these from last week with the new wire...




This thread shows the fitment, trimming, and results of the above pic...

http://www.jalopyjournal.com/forum/showthread.php?t=767491

 

All panels, patches, whatever are butt welded here at the shop, unless it's a factory seam. Overlap seams on outside skins tend to show themselves through bondo, glass, paint, etc.. on nice sunny days.

 

Anyone use the pulse feature on some of the new welders that is supposed to help with thin gauge?

 

I should mention also that if the panel was previously damaged and worked on from a hit and possibly stretched a bit even with smaller dents, Warping can be a pain to control. I had tis happen to me on my 50. The original panel was wiped and the replacement side was not. I got it in the end the best i could but was a bitch.

 

I've always butt welded, hammer welded with a torch,
but now that I have a TIG, my torch feels rejected!
Laps are for dances.

 

I'll agree with Tinbender. a good 00 oxy/act tip and you're good to go.
No need to skip around and let things cool, even shrinkage allows long runs if necessary without stopping.

And I'll add that (at least for me) learning to do it without blow-through was seriously frustrating, but well worth it.

 

Maybe you should learn to do things right using the proper tools and techniques commonly
used by many ten's of thousands of bodyman throughout the last 80 or 100 years.

After all is said and done, several hundreds of thousands of men before you have
used their intellect to overcome and master their God Given gifts of Hands and Mind
to become master of their (man made) tools.


Where do you fall short?
Are you openly admitting that your mind is not strong enough to master anything?

Are you just able to barely wash dishes????

------------------------


A very wise man once said, "Whether you believe you can or you can't, you are always right"

-He went on to become the worlds first Billionaire while others believed they could or couldn't wash the dishes.



Just sayin

 

Sorry if this is a silly question,but "lap welding" sheet metal is when you lay a good piece of sheet metal over the bad and weld it up?like putting a band aid on?

 

I have been doing autobody work for over thirty years. The first quarter panel I replaced on a car was a lap weld layed into a step made with a flange tool. I still have the car and the placement of the seam was between two beauty lines which helped to confine the distortion. The car is a convertible so it does see some moisture in the trunk. I havent had a rust problem nor is the seem visable from the exterior of the car. That said every panel replacement since then has been a butt weld. For me it takes the same amount of time and is much easier to work out the minor distortions without the additional metal present in a lap. The finished product also looks much cleaner. If I am working on a project where the customer demands that the panel appears to be a factory installed original panel it can be extremely difficult to do and a lap weld really is not an option. Most guys have a techinque they have developed over the years. I have found that careful fitment and the proper setting on your MIG and keeping the panel cool between welds are extremely important. The only time I will now have a lap joint is if I am using 3M 8115 panel adhesive. Its very strong and no heat is involved. You do need to tack a few spots but dang the stuff works. I would encourage my fellow rod builders to learn how to butt weld panels if possible. My .02

Dave

 

Ok yeah i googled it..I didn't think that was an actual technique.My buddy did the floors like that in his Plymouth.I told him it seemed crappy to lay the new floor over the old floor.

 

Incorrect! If the panels are of the same homogeneous parent material, thermal expansion will occur at the same rate.

 

I think most just do not take the time to properly set up a mig or their machine is a lower priced one that can't be fined tuned to the job. I much prefer tig or hammer welding but a mig CAN be set up to do a proper butt weld. Butt welds done right can actually save time on the back end if bumping or contouring is needed. My nearly 80 year old eyes and nerves sure don't win craftmanship prizes anymore but here is a butt welded panel on a transmission cover and some floor patch panels on a 57 Chevy that were done overhead; both with a mig machine that had time spent to get it close to right. I like the back side to look as good as the front side.

 

some people want to do it right, some people want to get it done and smother it with bondo.

 

only on Corvettes and Kit cars. but the fiberglass welder is expensive.

 

Use the proper heat range and tips. Combo of buttweld and hammerweld. You'll want to have lots of clamps on hand of every size. When the skills are built up it goes pretty quick. However, it can also become a 2-person job doing the hammerwelding. Yet, the finish can be absolutely gorgeous after finishing with pick 'n file work.

I think that folks don't want to spend the time building those skills up, practicing for a long time on scrap pieces of metal. I honestly can't blame them for that. Good fine skills don't come with anything but lots of hard work and time.

Just my 2 pence. That and a dollar MIGHT buy a very cheap cup of coffee.

 

Is this MIG welding done with a helmet or closed eyes?

 

A keyboard and mouse of course.