weld-grind-weld-grind or weld-weld-weld-grind-grind-grind?

here's another job I just started that can't be done with ox/acy. A 1/2 square tubing framed, removable hard top for a cabriolet....later to be covered with canvas top skin.

The tubing needs to be clamped tight/close to the back body during the 20 ga skin install.

I am using mig without flux.

Again, I think tig would be good for this job after tacking it all up with a mig.

I do have an old Miller Gold Star 300A tig/stick, but can't find a footpedal with the correct pin plug

 

Like skottyknukkles wrote, if there is no gap I turn up the machine to two gage sizes thicker than what I am working on. This gives really good penetration and makes a flatter weld (ie less grinding) than a cooler setting. If there is a gap then I use a cooler setting since the previous setting will blow a bigger hole. I also spot and cut around the perimeter, then grind lightly and then disc or flapper sand. Get it nice and flat and then it is easy to see where you need more weld spots when they start to get close to each other. Also, grinding and sanding in stages seems to help keep the metal cooler than doing it all at once and mentally it seems to take less time. Others are right, the MIG welds are hard as hell and take time to grind down. That's another reason I like the hotter settings, that makes for a shorter time on weld and the bead is nice and tight, small, short, whatever. If I absolutely know the metal will warp because it is long and straight then I'll TIG it so it can be hammer welded. That's my .02 senses LOL.

 

I mig everything with out a problem. ABSOLUTELY NO flux core. That crap is crap. 75/25 argon/co2. I clip my wire often especially if there is a booger. Clean nozzle and tip. And jump around often. What size wire are you using? What gauge metal are you welding? Excellent ground? Which way are you pointing your wire? Staying still while tacking or givvin it a lil wobble? Running it hot enough? Wire speed? How far is your tip away from the surface to be welded? Is your wire slipping in the feed?
Way too many things could be the cause of the pinholes you are getting. Get some practice pieces and play around with all of those options and you will find it.

 

weld all then grind I dont think it matters,I like the 75-25, no rust all clean DO NOT USE BRAKE CLEANER on parts your welding some kinds can put off deadly fumes. Ive also preheated with a small torch to help. live and learn pin holes suck.

 

Here is a great article written by Randy Ferguson on mig welding sheet metal:

http://fergusoncoachbuilding.blogspot.com/

 

def do not use brake cleaner youll end up in the ER.

Pre heating is important in some situations. if i am welding on a front beam axle i always pre-heat with a torch or map gas. reason being is that the weld will stick better. the axle acts like a big heat sink and was cast or forged at high temps. so i heat it up to be able to penetrate the welds. if that makes sense. sorry poor typing a explanation i have been up since 530 am.

 

take a look at the sedan i am building. its a welding nightmare. every inch has been welded. its going to need filler by the time i get done the whole car will be skimmed. fuck it might look like a glass body. but some times its unavoidable. you have to weigh it out, i dont ever expect to get more than 10-15 k when its dont if i sell it. but if i was building a 50k car i would start out with a perfect body and tig or gas weld every thing. but for ever day i use a mig. another thing is make sure that no moisture ever gets on the spool of wire. the least amount of oxidation will jam the wheels up in the machine i dont car if you have a homedepot special or a 3500 dollar miller. it will sputter and cause you alot of anxiety trying to figure out the problem.

 

This helps with the grinding woes.

http://www.airgas.com/browse/productDetail.aspx?Category=374&product=ESA130TF44

 

That Ferguson article was quite good, thank you for sharing.

 

I have used flux .035 and 75/25 gas with .025 wire and both did a good job . The flux will make more blow outs than gas will and flux is messy as hell ! If you can use gas go that way but flux will work fine , just turn the settings down real low .
First I tack weld the pieces in place then go back and tack weld everything up but making sure I keep moving to opposite sides from where I just welded to help keep the heat down . Also take breaks and having a fan blowing on the metal helps to cool down too . On floors I will tack weld then stitch weld them . I have used a grinder but the heat builds up very fast . A grinder with a flap wheel will let you grind longer but will still get very hot . I have found from someone else to use a die grinder and cut the welds down using the side of the wheel . It is very thin and you don't get the heat build up like the grinders do . That way you can get a lot more done without all the heat .
One the outside of a car the sheet metal will warp . You need to use a hammer dolly as much as you can to keep the metal in place . Doesn't matter how good you are , the metal will warp on a large piece . Smaller patches aren't too bad . Just be careful and keep a close eye on the heat of what you are welding . Just remember heat warps . Hammer and dolly fixes that !
Works for me !

Retro Jim

 

As far as the original question goes, most of the time I weld all of it and then grind. Another thing I do is use soft 4x4 wood blocks as dollies. They allow you to work the metal while hot. I weld 1/2 to 1" at a time and then stretch with a body hammer and the block. Just keep track of which direction the metal wants to crown and beat it the opposite way, hard enough to get it to the proper shape, but don't over do it. The block is just hard enough to work the metal when hot but the bead will sink into it allowing you to work it prior to grinding.

Also, keep a thin metal ruler handy to gauge what the metal is doing as you go. each time you stop welding, just before you start hammering, place the ruler on the flat unwelded portion or in a valley between two tacks to get an idea of what it's going to need. Once you get the hang of it, it goes pretty smooth. Later, after you grind, it aught to be close enough to fine tune it cold with a hammer and metal dolly. Lastly, don't get crazy grinding and overheat the metal. It'l warp it too and wear your safety glasses!

 

+1. The Esab wire leaves the weld soft enough to work like the parent metal. Makes good filler for tig welding too.

 

i always take the cone off first, then take tip off, clean tip real good with tip cleaner, wire brush tip and inside cone real well, m put tip back on and make sure its real tight, put cone back on, check gas pressure, and make sure you have good gas flow, start weld out on scrap peice of metal for about 2 inches solid, and i allways use tip dip after cone is hot, shake out excess tip dip, then get to welding, as long as your material that your material that your welding is really cean, and the groend cable is freshly cleaned with a wire brush and your ground is good and evrything should be fine. i allways tack my stuff first, then go back and weld about 1 inch at a time,jumping around yourarea to be welded alot and cool in between welds with an air hoe to minimize warpage, if it gets too hot leave it and let it cool down, thats where most people screw up by welding too much too fast, and everything warps and you end up having to do exssesive hammer and dolly work after that, and alot more grinding and filler work, patience is the main issue here! good luck!

 

What is the best way to clean/prep the edge of rusty pitted 18 gague sheetmetal to be welded to new steel. I having a problem with pinholes also with either welding process. I have bben using a 24 grit 2 inch abrasive disc. If I sand to much to really clean the metal edge it will be to thin for welding. soi what is the best way to prep this edgfe before welding ?

 

I didnt have a gas wirefeed a few months back so i started O/A ing and I love it, I wont go back. So my response is I DONT GRIND THE WELD, a little hammering while it's hot and a little fileing afterwords and it is perfect. Best of all, no pinholes

Now there still are some areas i'd wirefeed still, and i'd weld, snip, weld, snip and each weld would be a little round spot, and eventually they'd be continuious. I'd like to pick up a spool of .025 to try out sometime too

 

I only use TIG for sheet metal. Praperation is key, Clean metal, lots of tacks to reduse warpage while welding. I Hammerweld in about one inch long stitch's. Dollying while hot cools the metal quick but stops the warpage. The mass of the dolly takes the heat out of the sheet and the hammering counter acts the metal wanting to shrink.When i weld sheet i keep it cool enough to put my hand on at all times buy moveing where i weld all the time. in the end less grinding and body work. There is a realy cool gas hammerwelding video on the hamb

 

I tig weld myself, but would love to learn to gas weld. the way I do it is to first tack weld it all together then from the inside I weld it together, that way a lot less grinding is needed.

 

I read the Ferguson article as well, that is top notch work on that fender, question? He makes note of 'filing" as have some of the others that have posted. I have never tried this but I as well as others have said with a 2" roll-loc with a 36G disc will leave the metal thin around the welded area even after using a 1/16 cutoff to grind the proud area. Anyway, my question is what kinda file we talking about? Body file, rasp? I've love to know more about this, never to old to learn a new trick.

 

Hey Bobby D,

Filing ain't no ''new trick'' and infact is /was a very important part of traditional metal work i.e. metalfinishing. A body file, or known by its' trade name as a ''vixen'' file is about 12''-14'' long with curved teeth and can be either flat or curved. The curved file is also known as a ''shell'' file and is used on concave panels. The file is used to take bown hign metal on a repair, but its' most important job is to show the low areas from the high areas of a repair. The file is pushed or pulled across the panel at about a 30 degree angle and will hit the high areas first, leaving the lows inbetween. The low areas are brought up, and the panel refilied until there are no more lows or highs. The panel is next refiled in a crosshatch pattern, again from a 30ish degree angle, and it is this crossfiling that shows up any remaining lows or highs. Once corrected, the hand is used to final check the panel, and when no defects are detected the panel is disced with a 60grit closed-coat disc and ''buffed'' to finish. "if" you've done a good job welding,straightening & filing no silly high build primers or fillers should be required to prep for finish.
The problem with using grinders or Rolocs for ''finishing'' metal is that unless the repairman is very skilled he can remove too much metal from the repair, and leave behind high or waving metal requiring additional repair.

" A little putty and paint make a metalman what he ain't "

 

Thanks for explanation Pimp, by "new" I meant new to me, I'm sure if has been around a long time. Have to look into getting my hands on one and give it a try. Any particular brand, teeth count, etc to be on the look out for. thanks for the reply!

 

Hey BobbyD,

The standard body file runs about 14'' long and has about six teeth per inch, with teeth on each side and holes at each end to attach it to the file holder. You can find these at ebay, Snap off, Yeastwood, Ron Covell, Tinmantech, garage sales & swap meets. Look for places that sell aircraft repair supplies as these files are still in use for aluminum work.

As I mentioned above, the file is drawn across the panel at about 30 degrees across the repair to hit the high spots. Once the lows are bumped the panel is refiled, this time from the other direction crosshatching the repair. Try for a smooth , full pass with the file across the surface, not a choppy one. This filing pattern, when done well, will give a mirror smooth surface, and show any additional areas that need work, prior to priming. These files are also used to file solder (lead) but never on plastic filler, that is inless you wanna see a metalman's eyes bug
out?


" Humpty Dumpty was pushed "

 

I used to work at Nicholson File several years ago. We made those files and assembled them with the holders.
Now they're made in Mexico, Columbia or Brazil.

 

I would much rather TIG then anything else, but as they say if you can't be a good welder then you will learn to be a good grinder.

 

Watch the gap. If you are welding and then grind and leave holes then the weld is on the surface and not joining the two pieces together. This was hard for me to get in the beginning. I think gap has a lot to do with it. When I grind an area with a good gap it smoothes the weld to the level of the metal filling the gap and not leaving holes. It's hard to describe, so I hope that helps. It was a tough lesson for me cuz I wanted everything tight. I have found a gap about the size of the wire I'm running works best for me.

 

1) burping a gun (zap,zap,zap) just lays down cold starts. Not good.

2) gasless flux core isn't crap. Most people just don't know how to use it.

 

What I do when I'm ready to weld I pick out about three spot's in a 2inch area make about 3 small tack's in that 2inch area. Good hot tack's,keep a bucket of water beside you with a sponge, after you make these 3 tack's hit with the sponge not a lot of water welding and water don't sound good together. So just get the sponge wet and ring it out, after you make your weld's put the sponge over top of the weld's cool it down quick. With the hot tack's your grinding should not be as bad, plus this will stop almost all of the warping. It will take you a lot longer this way but you will come out better in the end. When I do any grinding I still keep the water and sponge there grinding can still warp the metal. Ok I've talked enough,just hope I helped.

 

Can someone explain to me how to hammer/dolly a mig weld on sheet metal? all I end up doing is making whatever warpage I have even worse. And what size wire do you mig guys usually run for sheet metal?