A tool holder assembly that includes a tool holder member adapted to be secured to a machine tool and a cutting insert support/clamp for clamping and supporting a cutting insert. The support/clamp member includes a plurality of serrations that are engageable with complementally formed serrations on the tool holder whereby a tight fitting engagement is achieved using removable fasteners. The support/clamp includes a clamping arm elastically movable towards and away from a support base and a clamping block connected to the connecting arm adapted to receive clamping forces from a threaded clamping bolt. The clamping bolt defines a force applying surface located in a first plane whereas the clamping block defines a force receiving surface located in a second plane, the first and second planes located at a diverging angle with respect to each other. The clamping block includes an edge portion engageable with a step on the tool holder that is spaced from the clamping arm. The diverging planes and the engagement of the clamping block with the stepped portion increases the force applied by the clamping arm to the cutting insert for a given adjustment of the clamping bolt and resists rollover of the insert.