What do you use to grind corner welds?

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Hi everyone, I'm in the middle of my first project and I have some fat/ugly corner welds on 2" x 2" tubing that I want to grind down to check for penetration and just to clean them up a bit.  My question is what do you guys use to get at these welds?  I have a few angle grinders with sanding, grinding, and cutting disks, but these don't seem like the right choice.  Would a flap disc be the thing to use?  Thank you for helping out a newb
Reply:Dustin, The best thing is to practice enough that you don't have to grind any inside corner welds.Until you get to that point, a carbide burr of the appropriate shape can work in a die grinder, or dremel type rotary tool.  Be warned, the slivers of metal a burr makes are VERY sharp, and get everywhere. I don't use it unless absolutely necessary. Good luck.
Reply:i use carbide burrs all the time, and as daddy says, they make very sharp slivers (i pull them out on a daily basis)  Ive found that slow speeds work better than fast speeds on a die grinder, they skip less (carbide burrs are very brittle, they can and will shatter  USE SAFETY GLASSES and face shield to be safe)i dont recommend you do this, but i do it on occasion.  i sometimes using cutting wheels on either a die grinder or angle grinder to grind stuff out.  You have to be extremely careful to not put very much side pressure on the wheel, because they are not designed to take a side load.  Its more making multiple slices out of the weld to reduce its size, then very lightly cleaning up whats left with the face of the wheel.Flap discs can work, but only if they are brand new, once the edge wears down there is nothing to cut with.Practice practice practice
Reply:A cheap crappy flap disk will stop working after new.  You'll still have plenty of paper, but it just won't cut well anymore.  I think what happens is that the grit comes off the material backing, and then the material is just buffing the surface.  With better flap disks, the material backing and grit wear evenly.  Some cheap brands work better than others, but sometimes you're better off to spend the money and get the expensive ones, rather than waste half the paper on the disk of a cheap one.
Reply:Sometimes I weld a part on backwards, or in the wrong placeI've found that a good method is to take the cutting torch and carefully scarf out the weld.  If you don't have a scarfing tip just hold the regular cutting tip paralel to the weld and carefully heat and blow out as much of the weld as possible without ruining the steel.  Then after you've weakened the weld enough, use a hammer and knock the part off.  Then you can grind everything down, and start over.If you're working with any corner, or obstruction which might cause the molten slag to blow back at you, wear a full face shield.  That stuff can go everywhere once you hit the oxygen."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Thanks guys.  I'll check into some carbide burrs and a die grinder...and practice those corner welds some more so I don't have to worry about it in the future.
Reply:If you're talking about grinding out a fillet weld, I'll reach for a 36 grit 3m Green Corps  4.5" x 1/8" disc.  I generally use the two corners on the grinder guard as pivots and either start at the leg in front of the grinder (as opposed to the leg underneath) and just pivot the grinder down across the weld, or I pivot back and forth across the face of the weld.  The Green Corps discs are much smoother grinding than regular black wheels, no wanting to skip around.  They also come in 1/4".The label on them is just adhesive backed paper. Peel the label off before use, otherwise when the disc wears down to the label you'll start smearing the adhesive all over the part.  Anything longer than 10 or 12" and I don't even bother with the grinder, reach straight for the air-arc.
Reply:Originally Posted by Static-XJIf you're talking about grinding out a fillet weld, I'll reach for a 36 grit 3m Green Corps  4.5" x 1/8" disc.
Reply:Die grinder electric or air.Also when welding a corner you weld TOWARDS the corner, not away from the corner.AWS certified welding inspectorAWS certified welder