MIG weld grinding on sheetmetal

[idrivejunk]

I have heard from multiple sources that flapper discs are great for this but have never had one in my hand. What have you tried and how did you like it?



This is how I do it when I'm working on exterior panel faces. All thats needed is a die grinder with a Roloc pad and stripping disc mandrel (can be made from a 1/4" bolt), and a DA or palm sander, as far as tools. The ones I use are all like $20 HF versions.

Here are the two key abrasives that maybe the other guy doesn't know about-







Here is a scribbling describing my techniques:





I can dig up some examples of welds I have finished and add those later but I'm not currently doing much of this on my project yet. I often do cars that are for show. Just wanted to see if I could get the conversation started. Feel free to ask about things I left out, or if I can provide more clarity.

[UGLY OLDS]

Looks good Matt ....

 Hey CHIMP ....Can this also go in the textbook  :?:  :?:  

Thanks ..
Bob..

[kb426]

Not bad for "scribbleys" .

[Crosley.In.AZ]

I bought a 4 inch flap wheel for my grinder.  40 grit.  Lowes had them on the discount table.  I had never used one

Not sure they are called flap wheels or layered flaps or what.

These are a cutting mo-fo.  I went back to Lowes, bought the others on th e discount table. 5  disc total.

[chimp koose]

great post ,and ya those flap discs can make metal disappear . I think they work so fast because as soon as the abrasive wears out it disappears and exposes fresh abrasive . The flap wheels for a die grinder don't seem to work the same way.

[idrivejunk]

Thank you gents.  

I never walk into stores so thats probably why I never find the new cheap and cool things.

I've found the fat cutoff wheel to be the only thing with enough precision and speed to be effective in my hands. Boss gave me that twist lock mandrel and I am developing an affection for the 2" discs. Those have resulted in some prettier rows of plug welds lately. But if I had to do it all with one tool, it would be the 3M 1991s.

I did toss things in a pile and take a pic of relevant tools and abrasives on hand. If I run across a group of pics that can further illustrate the technique and result, I will post those then. Feel free to show your stuff here, too!



So what textbook do you speak of, Bob? I'm slow to catch on  :oops:

[idrivejunk]

Here is a visual example of a recent before and after, where a rod was added to correct an aftermarket sheetmetal gap. Because this thread needs more close up MIG weld pictures! Of course a happy weld makes for a happy grinding experience.  DO try it at home!

[Crosley.In.AZ]

photo of my last  4.5 inch  flap disc i bought at Lowes.  Cut material faster than I thought they would

[UGLY OLDS]

So what textbook do you speak of, Bob? I'm slow to catch on

Chimp said that your post's had "textbook quality"..By asking him to add something to the "textbook" , I'm giving you a roundabout complement.... :?

Bob...

[idrivejunk]

photo of my last  4.5 inch  flap disc i bought at Lowes.  Cut material faster than I thought they would

Those do look pretty ferocious   Nice bargain grab.

I can't help seeing this image every time I hear that word...




That kind may also be fairly abrasive  

[idrivejunk]

[ I'm giving you a roundabout complement.... :?

Thank you sir, I'll take one of those    I just take them clumsily.  :oops:

You meant the ol' noggin library, I see. Much obliged, I aim to please but sometimes I gotta rush or grow weary. I wonder if schools still use books at all.   :?:  I'm just not out to 'school" anyone but I am (usually) satisfied with stuff I do. Muscle car sheet metal work is something I will probably always enjoy.

[idrivejunk]

Nobody else thinks flappers are hot?    

Placing these pictures here to more fully illustrate the technique described above. For reference. Today was the first chance I've had to create a visual guide. The steps on the brown pages    can be seen if these images are studied.











Switch to Roloc disc-





Then the purple wheel-



Then 80 grit on a 6" dual action palm sander that has a coarse pattern-





I applied some black paint for visual clarity. It could use a few touch up welds but as you can see, the seam disappears almost entirely without excessively thinning the metal around it. A steady hand is required but if you inspect my welds, you'll see that mine ain't so steady. The point is you'll need to exercise similar tool control as with welding, in precise grinding. You gotta be able to see it good. But the same hand that welded that did the grinding. Take your time and you can achieve similar results or better with time and practice.

[UGLY OLDS]

Neat  :!:  :!:   I never knew that the 3M wheels were that aggressive ...

Looking good ...Do you use "easy grind" wire in the welder or regular mig welding wire ..( ER70S I think)  :?:

Bob..

[idrivejunk]

its just plain MIG wire, .030 size on a 10 lb spool.

The purple wheels are harder / tougher than the black ones but really don't remove any steel to speak of. I use them not so much for leveling, more like cleaning and uniforming the surface. If it isn't flat, the purple wheel won't make it so.

[idrivejunk]

Oh and Bob... fwiw... Clean-n-Strip discs and similar ones are available in twist-lock or Roloc style... I haven't seen the purple ones offered that way though. Had some sample ones in the shop once, they were orange. I think purple 3M wheels are like $35 for a four pack, and they are a very versatile abrasive for any type of metal work. For example once they wear down small you can really clean some tight spots such as those found on castings.