A stump grinder for a powered cutting wheel attached to a boom is disclosed, wherein the improvement relates to a cutting wheel confinement system which includes a cutting wheel further comprising a coaxially disposed spindle extending from an unsupported side, and a boom which further comprises an opening which is centrally disposed with the spindle and sized so as to allow the spindle to freely rotate therein without contact when the cutting wheel is not rotating, and to allow for a predetermined amount of eccentric motion of the spindle before the spindle makes contact with the first opening, and which prevents more than a predetermined amount of eccentric motion of the spindle by confining the eccentric motion of the spindle via contact with the first opening.