A clamping apparatus comprises a chuck member and a collet member that includes, at its rear side, a peripheral shoulder. The top side of this shoulder is provided with a thrust surface adapted to engage radially displaceable clamping balls of the chuck member. The bottom side of the shoulder is provided...http://www.google.com/patents/US7429049?utm_source=gb-gplus-sharePatent US7429049 - Clamping apparatus for fixing a collet to a chuck
