New Welding Thread ?'s for beginners...MIG

[JoshStratton]

Hey all, and probably Matt since he seems to be the forum guru on this subject and may reply :)

I looked for a thread like this but didnt see one. I am guessing it fell off the board if one ever existed.

I am planning on doing some body work on my car. I have a small MIG welder that seems to do a decent job on thick stuff up to 1/4 inch.

I practiced with my welder by creating a body cart.
https://static1.pt-content.com/images/noimg.gif

https://static1.pt-content.com/images/noimg.gif

Now that I am about ready to work with sheetmetal, I wanna make sure I don't create a brittle mess of welds and I know that sheetmetal is a whole new animal from what I worked with previously. I will make sure my butts (hehe) are tight (hehe again), but I am not quite sure how to do the finishing welds after spotting every 6 inches or so.

I think I saw Matt mention in another post that with a MIG, you wanna find you setting and then pull the trigger on one spot for 2 or 3 seconds.

Instead of laying a bead when finishing thicker stuff, do you just create a series of spot welds all the way down the seam?

Would anyone have any pics of what the welds would look like before grinding them all off?

Also, what kind of penetration are you looking for with sheetmetal?

Should the weld go through the entire panel, or just 3/4 of it?

I am sure I will have more questions after getting some answers but I thought I would start with these.

[Travis B]

the method you are reffering to is called stich welding.....Get your peice tacked in good. Then go around the area slowly putting a series of tack welds back top back to back......(slightly overlap the previous tack weld) is the best way to describe it. I usuall to 1/2 to 3/4 of an in and move to a different area on the panel and work my way around! As far as penetration goes you shouldn't be able to see a gap on the back side of the panel. You want to be sure after you metal finish the area that it will have enought structure to hold it's self! hope that wasn't to confusing

[JoshStratton]

Thanks for the info! When you say you shouldnt be able to see the gap on the backside, should you be able to see the 2 pieces butted together or should the weld cover that as well (full penetration)?

With the slight overlap of 1/2 to 3/4's, are you saying that you put one spot down, then another on top of it before moving to a different place? I like that idea. Originally I was going to do that but was worried about warping. So, I decided I was going to just spot every 6 inches, then go around again and overlap the original spots one time. Then go around again, until they all connect. My biggest fear with this is that the weld would harden, and then the next time around I would just be piling it on the original spot instead of getting penetration.

If warpage shouldnt be a problem, I will do it your way. Cool beans.

Now here is another question. With my body cart, I wasnt too worried about how the welds looked. Do I need to actually dip this wire in the weld for sheetmetal, or should I let it burn off without touching? I think with a MIG it has to touch to get the ground, but I wasnt too sure.

[Matt@RFR]

Hey Josh. Yeah, welding bodywork is completely different than structural stuff.

To quickly answer one of your questions, no, structural MIG does not include individual spot welds, ever. That's just begging for a failure of one kind or another. I attached the only picture I have of one of my MIG welds. It's 1/8" mild steel.

To give you a real world example of how much spot welding would be frowned upon in the world of structural steel (bridges, buildings, etc.), anywhere a weld stops, the end of the weld must be ground down to the base metal before another weld is begun. And in multi-pass welds, starts/stops are staggered so they aren't in the same area.


,,,but I am not quite sure how to do the finishing welds after spotting every 6 inches or so.
Well, puting a tack every 6 inches is a good start. Then tack the joint every 3 inches. Then every 1 1/2". Then every 3/4", etc., etc..

Concerning the physical technique, once again we're talking about something that's pretty personal. It depends on your voltage/wire speed/wire size/stick out/gas coverage/metal cleanliness, as well as how well you can actually see what's going on in the roughly 1/2 second that the arc is on. I think most guys find that just pulling the trigger and holding the gun still works fine for them.

Penetration on 16-20ga and thinner should be complete, but for bodywork, I'm thinking it's not really required. Also, I'm not even sure the body guys completely weld the seems. You may want to check on that.

[JoshStratton]

Oh! In regards to preperation:

With the body cart, I grinded down the edges of the connecting pieces to create a gap when they were butted together. I then layed a bead in the grinded area to get a solid connection, then I did the looping )))) motion to finish it and get full connection. What would be the method of preperation for sheet metal? It is too thin to grind down this way, I would think. It sounds like the method would just be a series of spots instead of the bead and ))) method.

Hey Josh. Yeah, welding bodywork is completely different than structural stuff.

To quickly answer one of your questions, no, structural MIG does not include individual spot welds, ever. That's just begging for a failure of one kind or another. I attached the only picture I have of one of my MIG welds. It's 1/8" mild steel.

Penetration on 16-20ga and thinner should be complete, but for bodywork, I'm thinking it's not really required. Also, I'm not even sure the body guys completely weld the seems. You may want to check on that.

Thanks Matt. In that pic, have those been grind down? My welds are kind of piled up. I am pretty sure I got good penetration, but I think I didnt go fast enough and they were piling up.

Is that just a matter of slowing down the wire speed? I had my heat just about as high as I could get it. It is a small 110 welder. It isnt a Lincoln, but it looks like one. I cannot remember what brand. hmm....

[Matt@RFR]

It sounds like the method would just be a series of spots instead of the bead and ))) method.
Correct.


In that pic, have those been grind down? My welds are kind of piled up. I am pretty sure I got good penetration, but I think I didnt go fast enough and they were piling up.
No, the picture I posted is of an untouched weld. No grinding, no wire brushing, no nothing. The only time I grind welds is if something has to fit flush where a convex weld is.

A weld that sits too high is either too cold, or too slow. Yes, if you travel too slowly, the incoming filler will just pile ontop of the filler that's allready been deposited, resulting in no further penetration. It's a very dangerous habit to get into. If travel speed is too slow, then the arc never sees the root of the joint, which, again, results in fusion, but no penetration.

[Travis B]

Matt-

is that a continuous weld in the pic?

[Matt@RFR]

Yessir.

[Travis B]

WOW! very nice

just out of curiousity do you push or pull your welds?

[Matt@RFR]

Thank ya. :) Mostly I push, but it depends on the circumstances. Usually that boils down to how lazy I am that day versus required aesthetics. Generally, I keep things to within 15º or so of 90º, so there isn't much change.

[JoshStratton]

How big is that piece in the picture?

[Matt@RFR]

That is the long side of 1 1/2" x 2 1/2" x .120 rect tubing, the triangular parts are 1/8" thick, long leg is roughly 6".

[Travis B]

I am still trying to come up with how you got the nice dime looking pattern. I feel like I can weld pretty good mig and tig...at least I think I can.

What kind of mig do you have was it on any kind of special setting or.....am I not as good as I think I am..lol!

[Matt@RFR]

I have a Miller 251. No special settings, just a good solid setting for the material thickness, and a steady hand. A big part of it is being completely relaxed. I can carry on an in-depth conversation while welding.

I'm pretty sure I did that weld using a push/pull technique, as opposed to doing circles. Who knows, I change the way I weld every day. :) I get bored easily.

[Travis B]

regarding your comment about circles and other methods.....I usually try and make a solid pass no circles, no hesitations or anything like that! And my welds come out nice and smooth good penetration basically a nice consistent uniformed sized weld! But they don't have the nice "droppin dimes"look that yours in the pic has????

now i'm gonna loose sleep...thanks a lot! lol

[Matt@RFR]

Well, if you look at that picture again, there's two welds like you're describing. Those are called stringers.

There's nothing wrong with that technique, IF you move fast enough, don't get any undercutting, and still end up with the correct size weld. For those reasons, I usually stay away from stringers on fillet welds. It can be hard to get the weld size you want and still keep your travel speed up. Plus, using a pattern like a weave, circles or push/pull, it's easier to make a good looking weld on those really shaky days, or in akward positions.

[JoshStratton]

If you dont mind, there are a few terms in there that I would like to add to my metal glossery. :)

What do you mean by undercutting? Is that the same as blow-through?
What is a fillet weld?
Are the stringers the welds that go north-south in the pic? That is what I used on my cart before laying the circles (well, more like bloby puddles) on top of them.

[parsonsj]

On my body work welds I do the tack weld thing until the tacks are 3/4" to 1" apart. Then I run a set of stitch welds from one tack to the next. Pull trigger, release, move, pull trigger ... in about 1-2 second periods. You'll get a rhythm that lets the new spot melt into the old one with an over-penetrated weld which is perfect for grinding smooth for bodywork. Be sure and move around to reduce the warping.

Also, watch it when grinding the weld ... that heat can also warp panels.

jp

[Travis B]

that is what I was trying to explain...well put john

[JoshStratton]

Ahhh I get it now! So you don't spot all the way around next to each other? Do kind of what Matt was saying at 6" then 3" then 1.5" then .75" then lay a stitch to close them?

Thanks guys. I will give this some practice. If it doesnt work, I will try and post some pics to get some feedback.

[parsonsj]

Josh,

Yes ... that's how I do it.

One other thing to keep in mind about warpage: it is caused by heat from welding, but is also caused by the metal getting pulled in place. If you have a gap between the pieces of metal when you start welding, the molten puddle between them will shrink as it solidifies. That stress causes warping. That's why you want to get even spaced tacks all the way around and progressively close it so that the metal pieces don't move (as much) from the solidifying puddle.

jp

[Matt@RFR]

Key:

...so that the metal pieces don't move (as much) from the solidifying puddle.

For terminology, please see the attached drawing. It represents a section view of a fillet weld, also called inside corner weld.

Undercutting would happen, most likely, at the toe of the vertical leg of a fillet weld. It's when some of the base metal is pulled or washed into the weld, leaving a step at the toe of the weld. It's caused by lots of things...too hot, too fast, too shaky, etc.


Are the stringers the welds that go north-south in the pic? That is what I used on my cart before laying the circles (well, more like bloby puddles) on top of them.
The very same.

What you're talking about is a root pass, and a cover pass. You would probably have been fine running that in one pass, as long as you moved ahead and buried the arc in the root before filling up the rest of the joint, but it's hard to say without seeing your weld prep.

(EDIT): On that drawing, the 'fusion' arrow should be pointing at where the toe meets the base metal. I also wanted to mention that welds are sized by the length of the shortest leg, NOT the throat.

A good rule to live by is the weld should be as big (leg length) as the base metal is thick (thinnest member).

[Camaro Zach]

you can butt each tack up against one another but unless you get each tack right ontop of the other and get alot of heat on it you wont get 100% penetration inbetween each tack. here are some pics of what im talking about.

[JoshStratton]

Josh,
That's why you want to get even spaced tacks all the way around and progressively close it so that the metal pieces don't move (as much) from the solidifying puddle.

jp

Oh boy. Now that is something I would have never thought of. No wonder body shop guys make 50+ bucks an hour.



A good rule to live by is the weld should be as big (leg length) as the base metal is thick (thinnest member).

This rule would not work for sheetmetal, would it?....god I hope not. Something like 18 gauge would be pretty hard for me to do.

After seeing your definitions, I totally realize how ugly my welds are. They are too wide and have a lot of undercutting. Is this something that could possibly lead to a dangerous situation? I plan on using my cart so I can get under it and work. I had the whole car on it, minus the front sub, at one point. It has only gotten MUCH lighter since.

[JoshStratton]

you can butt each tack up against one another but unless you get each tack right ontop of the other and get alot of heat on it you wont get 100% penetration inbetween each tack. here are some pics of what im talking about.

Zach,

Thanks for the examples. I have actually been able to get a few sheetmetal welds to look like those! woohoo! I think my biggest issue is how I apply them to what I am doing and where to put them.

Am I seeing these correctly?

On the first pic, it looks like you bent the metal down and tacked the end so it would stick. That second pic looks like you did the rest of the tacking on the underside. Did you also lay a weld on the other side (which appears to be the outside of the piece)? What kind of weld did you lay down on the outside if you did weld that side? In that last pic, is that what it looked like when it was all grinded down and finished?

[parsonsj]

Hey Matt,

After looking at your picture, it seems the penetration in the diagram is shallow. Do I have that right? Is that enough penetration for a structurally sound weld?

Just curious, as I always want to learn more more more about this art/science called welding ...

jp

[Matt@RFR]

This rule would not work for sheetmetal, would it?....god I hope not. Something like 18 gauge would be pretty hard for me to do.

After seeing your definitions, I totally realize how ugly my welds are. They are too wide and have a lot of undercutting. Is this something that could possibly lead to a dangerous situation? I plan on using my cart so I can get under it and work. I had the whole car on it, minus the front sub, at one point. It has only gotten MUCH lighter since.
No, that rule of thumb pertains to any joint besides a butt joint. Butt welds don't have legs, so you're left judging the weld "size" solely by penetration.

There's two downsides to undercutting. 1) It creates a stress riser. Stress risers usually only fail when under cyclic loading/vibration. 2) At the deepest part of the undercut, if you can picture this, the metal is thinner there. So basically, if the weldment is over engineered with material selection, it will probably be fine.

I'll leave the decision up to you, as to whether it's safe or not. Too much liability involved for anyone but you to make that call.

John, that's a tough question to answer, since it depends so much on the end use of the weldment, and how it was engineered (additional gusseting, supporting elements of the weldment, etc.). But, generally speaking, my quickie drawing depicts good penetration.

You can test your own welds: Section the weld, polish to a semi-shine or so, and etch it with muratic acid, or equivelant. That will show you exactly what's in my drawing.

[parsonsj]

generally speaking, my quickie drawing depicts good penetration.

Very interesting. Thanks!

jp

[Camaro Zach]

Zach,

Thanks for the examples. I have actually been able to get a few sheetmetal welds to look like those! woohoo! I think my biggest issue is how I apply them to what I am doing and where to put them.

Am I seeing these correctly?

On the first pic, it looks like you bent the metal down and tacked the end so it would stick. That second pic looks like you did the rest of the tacking on the underside. Did you also lay a weld on the other side (which appears to be the outside of the piece)? What kind of weld did you lay down on the outside if you did weld that side? In that last pic, is that what it looked like when it was all grinded down and finished?
the pics got thrown out of order when i posted them. But the first pic shows an outside corner weld. basically i just cut all the way down the piece but left that 1/4 or 3/8" at the end to hold the 2 pieces together when i bent them, then i tacked the other side so the pieces wouldnt spread apart. The second pic shows the uneven penetration on the corner weld and the butt joint. the third pic shows the top of the butt weld before it was finished. and the last pic shows what they look like ground down (although i didnt finish the butt joint because someone needed the extension cord)

[JoshStratton]

What are your thoughts on using an auto darkening helmet? I had a chance to try one out for a few minutes a while back. It was some Swiss made brand that was not battery operated...i think it was Solar? I really like the way it worked, but didnt know if it protected enough to justify spending 350 bucks on one. I think it was called an Optima Sattellite.

[Travis B]

we have nothing but miller helmets in our shop they are worth there weight in gold! I can't weld without an auto darkening helmet! If you buy one just bite the bullet and get a nice one :naughty:

[JoshStratton]

They have a good price too.

http://cgi.ebay.com/MILLER-ELITE-AUTO-WELDING-HELMET-BLACK-216322_W0QQitemZ7574947411QQcategoryZ92090QQrdZ1QQ cmdZViewItem

[Travis B]

They have a good price too.

http://cgi.ebay.com/MILLER-ELITE-AUTO-WELDING-HELMET-BLACK-216322_W0QQitemZ7574947411QQcategoryZ92090QQrdZ1QQ cmdZViewItem


yup thats what I have but with some cool paint that is coming off....lol

[DRJDVM's '69]

This thread is great because... I just had my first welding lesson today !!!

There's a local trade school that does "private, byt the hour" lessons, so I went in today and got started. Today the instructor did a basic run down of MIG welding and then had me practice laying down beads for a "filler weld" (is that right ??). Basically an angle piece of iron where I just layed down bead after bead to build up a section.

There's definitely and art to doing this. Gettting my hand steady and going in a straight line at a consistent rate and distance is gonna take some practice. SOme of my welds looked pretty good for a first timer and other looked like crap.

I'd like to get a book to use as a reference when I have questions. I'm hoping this well also help me learn the vocabulary and some of the basics of what I need to do and why. Also there are some many variables when it comes to what your welding and why etc.

Any recommednations for a beginners book ???

[Matt@RFR]

"filler weld" (is that right ??)
Bead-on-plate weld. It's not a weld, actually. A weld joins two seperate pieces. What he's having you do right now is simply getting used to the sights and sounds of MIG welding. That's really all it's good for.

I don't have any books that I recommend. Too many of the books I read as a beginner have outdated material, personal preferences that the author states as fact, and plain bad advice.

[Texas Bob]

This thread is great because... I just had my first welding lesson today !!!

There's a local trade school that does "private, byt the hour" lessons, so I went in today and got started. Today the instructor did a basic run down of MIG welding and then had me practice laying down beads for a "filler weld" (is that right ??). Basically an angle piece of iron where I just layed down bead after bead to build up a section.

There's definitely and art to doing this. Gettting my hand steady and going in a straight line at a consistent rate and distance is gonna take some practice. SOme of my welds looked pretty good for a first timer and other looked like crap.

I'd like to get a book to use as a reference when I have questions. I'm hoping this well also help me learn the vocabulary and some of the basics of what I need to do and why. Also there are some many variables when it comes to what your welding and why etc.

Any recommednations for a beginners book ???


I just picked up my text book WELDING Principles and Practices 3rd edition by Sacks and Bohnart for about $70 used for an Intro to Welding class at college. 30 chapters and mega thick, I have no idea what I'm getting into but after reading 3 chapters (my wife called me a nerd as school doesn't start till next week) I can follow this thread pretty well and I have zero experience with welding.

Bob

[O&C Racing]

I just thought that I would throw out an opinion on machines. I've been using a Millermatic 185 for over 6 years now. I never really liked the fact that it had 7 settings for voltage. When working on thin sheet metal It needed a setting less than one but sometimes needed something in between one and two. So you would have to get creative with wire speeds to get a good weld.

So over the weekend a friend needed a welder to replace his, so I sold him my 185. I ordered a new Millermatic 251 and it got here today. So I set it up and started welding on some scrap of varying sizes. The only thing I can say is this thing rocks. The arc is much more stable and it welds sheet metal like a champ. It also laid down some nice welds on 1/4" stuff with ease. I would highly recommend this to anyone looking to purchase a new machine. I got it from cyberweld.com for a hair over $1700 with free shipping. None of the local dealers that I deal with would come close to matching the price and not having to pay sales tax was a bonus as well.

Now I just need to do something with this 180 SD Tig Runner I bought last year. I think I'm ready for an upgrade in that department as well. Just need to do some more research on Tig machines.

Curtis

[JoshStratton]

Hey guys. I wanna bring this thread up again if that is ok.

I welded my first body panel last weekend and I think it turned out pretty well. I grinded the welds down so any pics I would get probably wouldnt show much.

However I didnt get any warpage, the penetration is nice and it seems pretty solid.

I wanted to thank you guys for all your help (Matt and John especially while not discounting the help from others).

I still have 2 questions though. I did the spot weld pattern of every 3 inches, then 1.5 inches, then .75 inches, then a finish bead. The finish bead is what I am not sure about. I mean it turned out nice, but I think I could have widened it more. I was welding 18 gauge steel to 20 gauge steel with a half-circle pattern ))))) on an overlap joint. The beads were not even 1/4 inch wide.

With steel that thin, do you think I can widen that or should that be enough?

Also, after grinding it all down, there were still a few small gaps in the weld scattered around. For finishing body work that will be seen, such as this, should I go back and fill those in with spot welds or do body shops just putty over them? Basically, I guess I am asking how to account for these.

Thanks!!


EDIT: Let me correct my language above. The gaps are not in the overlap joint, I am really not sure how to describe them. There are small holes where the weld did not fill in. Man I hope someone knows what I am talking about. LOL

[Camaro Zach]

IMO you should fill them all in, not only does it make it look better but will reduce the number of weak spots and will prevent any moisture from seeping in under the paint/filler

[JoshStratton]

Ok. Will do. Thanks!
I am just glad you knew what I was talking about. :)