Ok I know this should be tucked away in the How To section , but its too cool to hide ,especially if you have never used one. You can buy these at the welding supply places. They are like a regular disk that fits a 4'' grinder. They are hundreds of little pieces of sandpaper glued to a disk. With a regular grinding disk if you touch a piece of pipe wrong it will cut a groove in it really quick . With these they will grind down a weld quick but are really forgiving if you bump something you dont want ground. They cost the same ,about $5 a piece. really smooth out metal.