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

What do you guys do? Do you weld in your sheet metal completely then grind all of it? OR grind your spots as you go. Seems you would get less pinholing if you grind your spots as you go and better penetration.

PS-or how about: clip,spot,grind,clip spot grind?

I'm trying to eliminate pinholing, explain your results!

 

Mig process - hot spot weld, partial grind (remove just the tops of the tacks), hammer and dolly to correct any shrink or warp, repeat with the next set of tacks. We are talking sheet metal, right?

 

pinholes? Did you run out of gas? Forget to clean the metal before welding? Pinholes are caused by contamination of the weld, not lack of grinding.

 

I gas weld sheet metal. Far less grinding, no pinholes. Pinholes in MIG are most often caused by cold start. If you have pinholes you have poor penetration at the start of each new weld.
You need to weld hotter, or better yet GAS WELD it!

 

X2! It's time to dump the "squirt-gun" welder and learn to handle a torch!
No pinholes, and no silly grinding that leaves the metal hard & thin!

'' Meanwhyle, back aboard The Tainted Pork"

 

Two of the best post on the hamb this week

 

I used to gas weld all sheet metal untill I bought a mig welder, now I'm back to gas welding. I can control the warping better, the grinding is not so much as it seems that the weld bead is not as hard.

 

i think he means pinholes from the welds not being close enough together?

 

Old Relics. Please post a photo of your "pinhole" problem.

 

I'm not much of a welder but, I'm getting to be a hell of a grinder.

 

pics would def help.

 

I T.I.G weld sheet metal .I'll weld an inch at a time,moving around a lot.Then I hammer and dolly the welds before moving on,stretching it where it shrunk from the welding.Little warpage and no grinding. If you're stuck on M.I.G welding,sounds like you need to clean your tip or turn up your regulator.

 

I have clean metal and gas.

I've tried and tried, got the smallest tip I can get for Smith torch, it welds but can snap apart a weld no problem, really brittle. I've played with the flame lots. I gave up.

Yes, thats it, because if you spot right next to a spot you are either gonna weld partially on top of it(less penetration) or leave a tiny gap which only shows through when you backlight it.

 

They wouldn't show with a camera, and you have to backlight even to see them.

 

i have that happen too. some of the holes you cant even see unless you put a flash light to it at night. if i am in a hurry i dont worry about it. but if it has to be perfect i use a sanding disc to grind the welds down. then weld again. moving toward the previous weld. the sanding disc i use is the kind that looks like a turbine. keeps the metal cooler. im sure theres a proper name i just dont know what that is.

 

i know it looks f-ed up but imo i think it helps keep the filler set in better. almost like it has some thing to bite into. if that makes sense? or just call me crazy

 

Maybe you should make a video tutorial for us squirtgunners....

 

Say what you will about mig welding, but I can gas weld as well - quite proficiently I might add, but gas hammer welding I find to be no faster than correctly doing sheet metal welding with a mig. I've been doing both for quite awhile though. I do understand that the weld from a gas weld is quite a bit softer, and that can be an advantage, but it just comes down to what is comfortable to the guy doing the work. Someday I will own a TIG, but that will be in the future when money is less of an issue.

 

That could be my new signature

 

Potential to be a great thread here.....

 

I have always heard those referred to as flapper wheels.

 

grind more before you weld. raced my uncle with a torch and coat hanger, I had the mig we were filling holes in the firewall of a pickup cab . not only did he fill more holes but needed less grinding! that said although i'm good with the torch, i still use my mig. i've found 1/4" welds spaced 2" apart and cooling each weld with a blow gun. i cool it enough to touch in between welds eliminates warpage.

 

if i can i turn the heat up about 2/3 of the way even on sheet metal. rather than hold the weld for lets say 5 seconds. i zap it for 1 second. just to the point where it wants to burn through the metal. but in some cases where theres a gap i turn the heat down so i dont blow the edges off. its all trial and error which i am still doing even after 15 years of this shit. i have a tig welder and i have gas welding equiptment but always use my 110 mig for sheet metal. but there are people out there that gas weld and dont use any filler when they are done. i just havent met any of them yet.

 

Great question!
I'm new to this and am doing it as a hobby so time is not a real concern.
I've been happy with a doing few layers of MIG tacks, some grinding, more tacks, more grinding, on and on 'till it's done.
I found with the TIG, things need to be really, really clean and you can't just sit down and weld a bead because of heat build up. That was without a pulser. My new welder does have a pulse option so I'll have to give that a shot.

Questions for the MIG welders. Are you using flux core or gas? Using argon, a mixture of, or ??

 

To me it really matters what the part is and where it is.

I can gas, tig, mig, they all have a place where they work best.

If it is a part that I can get to the backside to hammer and dolly I will almost always tig it.

If it is a part that it is cost prohibitive to get to the back side I will mig it with spot welds and keep it as cool as I can to minimize shrinkage.

 

I always use gas with my mig, especially on sheetmetal.

 

Always use gas when possible. Flux core never comes out as nice, at least that has been my observation. The cycle that you use of doing some welds then grinding always seems the best way to do it for me, plus it makes the task seem less repetitive.

 

I bought my Miller 35S mig used a little over 30 yrs ago and I am still practicing


Back to topic; There are some jobs that can't be done with ox/acy and if you don't have a tig, then it needs to be done with mig...and yes, ending up with some pits in between welds.

Here are a few pics of "wood to steel frame" conversion on a 2dr conv sedan.

The first pic shows the top edge of the rear quarter. It is just a bent over 3/4" wide piece at the top to nail to the wood. I bent some 18 ga then used a stretcher/shrinker to curve it to fit on top of the flimsy flange.

I now need to weld the inside 90 degree crotch of an upside down T shape. Impossible with gas due to warping, impossible to dolly. A tig would be best, but I used a mig.

Some other edges on these pieces could be done easy with gas, but I prefer the mig for this.

Last pic shows the other side of the car, and expand the pic to huge size to see the "pits" left by mig welding in short hits. Not a good thing, because those pits or craters are hard to clean without spot blasting, and could cause a paint bubble later. That's why I think tig would eliminate that possibility.

Grinding these parts: Most rough work done with 4.5 angle with hard wheels, sometimes using worn ones to get into areas, some done with 4.5 cutoff wheel, or die grinder cutoff wheel, and then finish work with flapper on a 4.5.

 

i use 80% argon 20% co2 in my small migs.

 

Nice work F&J! Nice to see someone else doing fine work with the equipment we have.