Abstract: A dental tool handpiece is provided with a spacer member which may be inserted into the collet of the handpiece which normally receives the tool and which has longitudinal slots adapting the collet to grip the tool when in operative engagement therein. The spacer member adapts the handpiece assembly to receive a shorter tool member within the bore defined within the collet, and when a tool member whose length is too short to reach the normal abutment surface must be operatively engaged within the collet, the spacer member may be inserted therein to shorten the depth of the bore and provide a substitute abutment surface for the shorter tool member. The spacer member includes a handle portion which is located to extend to within one of the longitudinal slots of the collet in order to facilitate guiding of the spacer member in place within the collet.

Abstract: In a tool holder assembly for a reciprocating dental tool including a hollow tool holder defining a tool holder chamber therein within which a dental tool may be mounted, a clamping mechanism is provided whereby a plurality of clamping balls are located about the periphery of the tool holder in order to impart a radial force to a tool body positioned within the holder. The tool holder includes a plurality of bores extending to its internal tool holder chamber and a clamping nut having a conically shaped inner surface engages the clamping balls and imparts thereto a radial force so that the balls, which are loosely mounted within the bores, may extend to within the tool holder chamber to clamp a tool therein.