An axle boring assembly includes a portable power head or drive unit, a bearing pack to which the drive unit is attached, an adjusting base to which the bearing pack is adjustably secured and a mounting assembly which fits over a motor vehicle axle and to which the adjusting base is secured. The mounting assembly comprises a first section having axially spaced apart front and rear clamps and a substantially identical second section with matching spaced apart front and rear clamps. Threaded fasteners extend between the front and rear clamps and may be rotated to secure the mounting assembly about the end of the axle. Each clamp includes jaws which contact the axle and which may be selected from sets of various sizes and configurations to ensure accurate and suitable engagement of the axle.