A tree stump can become an unsightly part of your landscaping decor. You can use a chainsaw to grind the stump down to the ground or you could use chemicals to rot the stump. Alternatively, you can convert the stump into a rustic outside chair. Before attempting to shape a stump with a grinding wheel, make sure you feel comfortable using this tool and know how to use it safely.
Draw a 16-by-24-inch rectangle on top of the tree stump. Position the front of the rectangle at the front of the stump. If a rectangle of this size will not fit on your stump, shrink the size but keep the dimensions proportionate to each other. The space remaining on the right side of the rectangle will make up the right armrest. The space on the right side will make up the left armrest and the space left on the back end of the rectangle will make up the backrest.
Grind the wood out of the rectangle with an angle grinder equipped with a grinding blade until you grind a cube out of the tree that extends approximately 12 to 24 inches deep, depending on how high you want your armrests to sit in relationship to the seat.
Take your time grinding. You will likely go though several grinding wheels. Start at the front of the rectangle and grind downward several inches. Work your way over until you remove a strip from the front of the tree stump that extends down to where you want the seat to be. Repeat this as you work your way to the back of the rectangle.
Smooth over the sharp corners of the seat with the angle grinder. This includes the front edge of the seat, the top edge of the backrest and the edges of the armrests. To do this, roll the grinder over the edge to create a slight radius. This is called "rounding over" and it converts square edges into rounded lips so the edges do not hurt people when they sit on the chair.
Seal the seat by applying two to three coats of polyurethane with a paintbrush. Paint the polyurethane onto the portions of the stump not covered with bark. If you choose a weathered look, do not add any protective coating to the chair. Over time, the chair will turn a weathered gray as the cut wood ages.