Limit the bending moment

Bending moment is an important consideration in machine tool spindles because it causes the tool to separate from the tool holder or the tool holder to separate from the spindle is discussed. A bending moment exists in a mechanical structure when an applied moment causes that structure to bend. All tool/spindle connections have bending moment limits, beyond which the connection may break or the tool holder pulls out of the spindle. Different styles of tool holders exhibit different responses to applied bending moments. Bending moment, a static load was applied to the end of the tool in a test stand and the resulting tool rotation was measured. The HSK connection derives much of its stiffness from the face contact. The separation happens gradually along the tapered surface. The curve for the CAT connection is almost a straight line, meaning that there is almost no stiffness change in the connection as the bending moment increases.