Abstract: A cost effective and reliable automatic balancer for high speed applications reduces the impact of unbalanced rotary tools and other devices. The automatic balancer provides a housing within which is defined a race. The race is accessible through a lid which removably covers one side of the race, allowing access to this cavity. A curved section of the race has a radius somewhat greater than that of a spherical compensating mass. The osculation region, where the compensating mass and curved section of the race meet, is carefully sized so that the surface area of contact is sufficient to prevent undue wear on the race, yet not so extensive at to result in excessive frictional contact between the compensating mass and the race. A lubricating fluid, filling at least a portion of the race, passes the compensating mass easily, due to the relative sizes of the compensating mass, the cross-sectional area of the race and the size of the osculation.