The D 76 SP four-wheel-drive stump grinder has a 76-inch boom swing arc for more grinding and less repositioning, says Morbark. It transfers 95 percent of the power from the engine to the cutter wheel, and the hydrostatic system has 3:1 cooling capacity. The cutter wheel has a hexagon shape for low resistance and friction. Eight cutter teeth have four cutting edges each, which can be rotated for maximum life and changed quickly. It is powered by a 62-hp Caterpillar diesel.