Abstract: A self-contained mount, for a spindle-driven rotary abrasive tool or the like, able to compensate for slight non-concentricity of the threading on the end of a drive spindle for the rotary tool. The mount includes an internally threaded cylindrical sleeve with an outside diameter small enough to be inserted into a longitudinal axial bore in such tool, and a retaining ring to maintain the sleeve fixed longitudinally therein while permitting it to adjust its position relative to the rotational axis, if necessary, upon being screwed onto a threaded end portion of the spindle, while supporting the tool coaxially therewith.