Finishing your weld?

[Ricoch3T]

How many of yall finish your welds when doing floor pans or splicing panels together?
If you do what is the proper technique for doing this without getting the weld or metal too thin? I've seen some people finish butt welds and such that look like they didn't put a patch in at all and I've tried myself on some scrap metal but it seems to be too thin when I welded it when i'm done.

[hotrdblder]

tig, weld is way softer and way easier to work

[Ricoch3T]

Thats what i hear, and I've been to another metal working forum before where some of them even recommend gas welding. But even with the mig I should be able to make a seamless weld and finish it without pinholes or problems where the metal is thin and weak along the seam correct?

[hotrdblder]

yes you should but with mig it is hard to do, everything has to be perfect, gap, prep,torch height, etc, then grinding needs to be done carefully, i am not sure why your so worried about it i would grind it down then skim it with filler and have a day

[rocketrod]

Thats what i hear, and I've been to another metal working forum before where some of them even recommend gas welding. But even with the mig I should be able to make a seamless weld and finish it without pinholes or problems where the metal is thin and weak along the seam correct?

I wouldn't sweat it, whether you are using mig or tig, just take your time and either will be fine.

[Mathius]

yes you should but with mig it is hard to do, everything has to be perfect, gap, prep,torch height, etc, then grinding needs to be done carefully, i am not sure why your so worried about it i would grind it down then skim it with filler and have a day

I concur. I will probably not be grinding down my welds on my floor pan. They are ugly, and the wire I used leaves a very hard weld, but the inside will be covered by carpet, and the underside can be rhino lined or something.

I didn't have a plasma cutter, or any other great cutting tools, nor did I have exactly factory floor pan replacements, and several other factors that led me to have to lay down some pretty sorry looking welds. There were places where I had to span a 1/4" gap with 0.23 wire. Talk about a pain. You want the weld to come out looking pretty too?

I think about the only chance of grinding all your welds, is if you are very patient, have a lot of skill with an electric grinder, and finish it off with an air angle grinder and a roloc disc.

I care more about my floor being solid for the first time in 3 years, than I do about what it looks like. When I do some welding on a body panel, then I'll take the time for finishing details like that.

Mathius

[Ricoch3T]

That was my main concern strength. I had your same situation on the floor pan, but I'll be knocking the weld down a little (leaving a decent size bead). I didn't know if there were any metal workers on here that could shed light on finishing it and having the strength to boot. When I usually finish one I take time to only hit the weld and not the surrounding metal, then finish with a polish pad. It leaves a nice surface but sometimes the weld area is thin.

I concur. I will probably not be grinding down my welds on my floor pan. They are ugly, and the wire I used leaves a very hard weld, but the inside will be covered by carpet, and the underside can be rhino lined or something.

I didn't have a plasma cutter, or any other great cutting tools, nor did I have exactly factory floor pan replacements, and several other factors that led me to have to lay down some pretty sorry looking welds. There were places where I had to span a 1/4" gap with 0.23 wire. Talk about a pain. You want the weld to come out looking pretty too?

I think about the only chance of grinding all your welds, is if you are very patient, have a lot of skill with an electric grinder, and finish it off with an air angle grinder and a roloc disc.

I care more about my floor being solid for the first time in 3 years, than I do about what it looks like. When I do some welding on a body panel, then I'll take the time for finishing details like that.

Mathius

[BRIAN]

I disagree, you can finish a mig weld to a where it will almost disappear. Tig and gas welds put in heat but the weld is not brittle and can be worked. A mig weld needs to have perfect prep and it can come close especially on a floor.


Penetration and preperation are the key. Buy a set of the orig Panel Clamps as they will give you the perfect gap which is roughly the thickness of the panel or a little more. You have to skip around but you also have to have the weld penetrate rather than what you see all over the web. You see tons of big names that grind the crap out of these lumps they call welds. That type of weld will crack when ground down. Also do not use a grinder or 36 grit disc to prep the panel or you will thin out the edges. Pulse your welds letting the weld just start to turn from red and hit your next. You will be surprised with better prep how clean your butt welds will be.

Sheetmetal welds take lots of prep to get them right. Don't just cut a piece and pull the trigger.

I have pics but they say they are too large. If you want I will email a pic and you tell me what I used.

[Mathius]

I disagree, you can finish a mig weld to a where it will almost disappear. Tig and gas welds put in heat but the weld is not brittle and can be worked. A mig weld needs to have perfect prep and it can come close especially on a floor.


Penetration and preperation are the key. Buy a set of the orig Panel Clamps as they will give you the perfect gap which is roughly the thickness of the panel or a little more.

Not accurate. If you don't have the panels cut to the proper size and shape, panel clamps aren't going to help you. If you don't have good cutting tools, cutting the panel to the right size and shape can be a PITA.

Mathius

[BRIAN]

Not sure what that means about not cutting correctly?? If you do not have tools to cut sheetmetal you are about 5 steps behind and do not need the welder or clamps??


Simple shears or $2.00 cut off wheel on your grinder are about all you need.

[Mathius]

Not sure what that means about not cutting correctly?? If you do not have tools to cut sheetmetal you are about 5 steps behind and do not need the welder or clamps??


Simple shears or $2.00 cut off wheel on your grinder are about all you need.

That's because you're obviously basing everything on your own setup. 0.23 wire is going to need a VERY precise gap as opposed to a bigger wire, because your tacks are going to be smaller. You may even choose to run a bead over a short distance with 0.23 wire.

Grinder is not that expensive, but a compressor is. Not everyone has access to one that is going to run a die grinder. They take LOTS of air.

You can go electric, but I personally have never seen an electric die grinder. I know they must make them, but it isn't something you're going to find in a local store.

You can use a sawzaw to cut the old material out of the car, but you can't use it to trim your patch panel. You'll vibrate the hell out of the panel and cut nothing and probably hurt yourself.

Big angle grinders aren't going to give you precision cuts.

Etc. etc. etc.

You're right on one thing, preparation is 100% more important than the weld itself, if you intend to grind it down. But once you've cut a panel too short, you either have to keep cutting and make another patch panel, or try to span the gap with whatever wire you're running, which is a lot harder to grind down.

Mathius

[Karch]

Makita and Milwaukee make electric die grinders. In fact, at a very reputable advanced porting shop, when they hand grind, they only use the Milwaukees...and these things are heavy and something like 11 amps.

[RobM]

Use a die grinder with a wheel, grind perpendicular to the weld. I use this kind of wheel... http://www.autobodytoolmart.com/imag...um/4290_91.gif
with this kind of grinder....http://buy1.snapon.com/catalog/objec...8400/48363.JPG

get the weld down flush with the surrounding metal then finish the weld with what’s called a "roloc" disk (I like a 50 or 80 grit wheel) on a 90 degree die grinder,

for this i use this kind of disk....http://www.autobodytoolmart.com/imag...arge/11323.gif

with this kind of grinder....http://buy1.snapon.com/catalog/objec...3600/43542.JPG

when doing this grind parallel with the weld. This should take very little metal away all your doing here is getting rid of your grinding marks and leveling. if you really want it nice DA over every thing with 80 grit sand paper. Then finish with body filler or seam sealer.

this is pretty much the standard technique in most automotive fabrication in my opinion

[Ricoch3T]

Thanks for the info. I have been doing something similar to this (after I'd been doing some reading and slowly figuring it out on my own) but I noticed sometimes I still get some pinholes in areas where either I didn't penetrate the metal enough or didn't have enough heat. Most of the floor pans and stuff I can weld on both sides tho if it doesn't look like it penetrated enough.

Also it seems like with the mig welded it is capable to fill in bigger gaps. I'm one of the unfortunate people that can't follow a line with the body saw i'm using. Cut off wheels work better for me I've been finding out but didn't know that until recently. Also the body saw is quicker. But anyhow the mig WILL fill in a gap, it just takes time and the ones I've looked at knocking down you need to make sure you didn't build up on only one side (the side you grind down). So say I fill in a gap from inside the car, naturally most of your weld will be inside the car with you, if you look at the underside you will notice that its welded and strong, BUT there will not be enough material left after you grind it. The underside will also have to be welded to achieve a solid surface for grinding.
Of course this takes more time than if you did it correctly with a small bead and tight gap.
Thats my opinion on the subject anyway. I might be wrong though. I'm still learning with the sheetmetal myself

Use a die grinder with a wheel, grind perpendicular to the weld. I use this kind of wheel... http://www.autobodytoolmart.com/imag...um/4290_91.gif
with this kind of grinder....http://buy1.snapon.com/catalog/objec...8400/48363.JPG

get the weld down flush with the surrounding metal then finish the weld with what’s called a "roloc" disk (I like a 50 or 80 grit wheel) on a 90 degree die grinder,

for this i use this kind of disk....http://www.autobodytoolmart.com/imag...arge/11323.gif

with this kind of grinder....http://buy1.snapon.com/catalog/objec...3600/43542.JPG

when doing this grind parallel with the weld. This should take very little metal away all your doing here is getting rid of your grinding marks and leveling. if you really want it nice DA over every thing with 80 grit sand paper. Then finish with body filler or seam sealer.

this is pretty much the standard technique in most automotive fabrication in my opinion

[RobM]

A lot of people have their own little tricks of the trade…. Its all about trial and error and practice.

One thing to remember is a nicely finished weld is a lot like Nice body work its all about the prep!

You need a nice tight (yet relaxed) gap.
When I say a relaxed gap I mean the gap has to be tight but not too tight. The panels being welded can’t be pushed together to hard. You don’t want an interference fit here. The reason for this is because if the panels are bitted together too hard they will warp badly when you put a lot of heat into them. A badly warped weld is hard to finish out with out turning the surrounding metal into tin foil. So again a tight yet relaxed seam is where its at.

I suggest first tacking the panel in before the seam gets fully welded. First put tack on the corners to keep it in place then alternate tacking all the sides of the panel until you have a tack about every 1.5-2 inches of the seam.

I have better luck stitch welding the panel as opposed to just doing one long bead. This entails doing a series of tacks one after the other to create a bead this allows the use of much more heat and results in better penetration. Make sure to make one tack after another before the previous one cools enough to not be cherry red any more. Also push into the weld with the gun don’t pull…..if your welding from right to left angle the gun to the right this will also help penetration.

Use this technique to fill in between those tacks that are 1.5-2 inches apart. Keep the welds only 1.5-2 inches long will keep warping under control. Skip around the panel try to prevent putting a lot of heat into one area. After a weld is completed cool it down with compressed air if possible.

before you weld make sure what your welding is clean. This will help all aspects of the weld. I can elaborate on this if you want

[80proZ]

I'll agree with most of what RobM said except the gap.You need a slight gap(about .023 mig wire) around the entire patch.
What will happen when you start to tack is the weld will cool and shrink,drawing the patch closer to one side of the hole and leaving a larger gap on the otherside.If you make the patch to tight,it will make the seams rise above the surrounding area,making it much harder to make dissappear.
TIG welding floor pans would be a waste of time IMHO.The seams and surrounding area would have to be spotless to make a good weld.Welding with a MIG is much more leinent and forgiving than the TIG.And grinding it down takes very little time.Personally i use a 4 1/2" grinder and cutoff wheel to do all my cutting and a 120 grit flapper wheel to grind down the welds.
I just finished some patches on my floors today,except for grinding, i'll post some before and after pics tomorrow.

[Mathius]

Use a die grinder with a wheel, grind perpendicular to the weld. I use this kind of wheel... http://www.autobodytoolmart.com/imag...um/4290_91.gif
with this kind of grinder....http://buy1.snapon.com/catalog/objec...8400/48363.JPG

get the weld down flush with the surrounding metal then finish the weld with what’s called a "roloc" disk (I like a 50 or 80 grit wheel) on a 90 degree die grinder,

for this i use this kind of disk....http://www.autobodytoolmart.com/imag...arge/11323.gif

with this kind of grinder....http://buy1.snapon.com/catalog/objec...3600/43542.JPG

when doing this grind parallel with the weld. This should take very little metal away all your doing here is getting rid of your grinding marks and leveling. if you really want it nice DA over every thing with 80 grit sand paper. Then finish with body filler or seam sealer.

this is pretty much the standard technique in most automotive fabrication in my opinion

Man, I don't know if I'm using the wrong wire, or if I'm just buying crappy grinding and cutting discs, but I ground away with a 4.5" angle grinder today on one of my welds and couldn't level it. Didn't want to go too hard, because it'll just destroy the surrounding sheetmetal in the process. Took it down as far as I could, roloc 36 grit sander, and still couldn't clean it up.

I have a flap disc I could try.

Mathius

[80proZ]

Here's some patches i finished up to day
This one is right where your right foot would sit if not on the pedal

finished and ready for some primer

the following is a series of pics from start to finish of another patch i did just below where the dimmer switch is located on an 80 camaro,which is what im restoring/modding.





both these patches took me a total time of about 3 hours from start to finish.including the time to fab up the patch.The first one took the longest to fab as it has a nice compound curve to it.
Hope these help alittle

[Mathius]

Here's some patches i finished up to day
both these patches took me a total time of about 3 hours from start to finish.including the time to fab up the patch.The first one took the longest to fab as it has a nice compound curve to it.
Hope these help alittle

Those pictures look like you're using something like .030 or .035 wire?

I wonder if maybe the 0.023 wire is too small and makes grinding harder. It seems like I end up having to run a weld on both sides of the panel, rather than just one tack that holds both sides, because of the wire being so small. I wonder if that is the problem. Maybe there's more metal concentrated at the weld, than a simple large tack that would spread out.

I'm working on an inner fender right now that the battery tray area has rusted away on my '76 Malibu.

I'm contimplating throwing a few tacks on it to hold the patch in place, and then taking it over to my buddy's house and welding the rest of it up on his bigger machine and seeing how those welds grind down.

Mathius

[80proZ]

i'm using .023 wire.ER70s alloy
What about your heat and wire speed?What kinda welder?What alloy wire?