BUSH HOGĀ® PLANETARY HYDRAULIC DRIVE POST HOLE DIGGER MODELS: PHDHC20, PHDHC30 AND PHDHC35 The Bush HogĀ® Planetary Hydraulic drive features a high torque level to power the auger through the most demanding conditions. All augers are heavy industrial grade with 3/8-inch thick flighting. Sized in diameters from 6-inches to 36-inches (depending ...