In a chuck adapted for connection to a processing machine and composed of a connecting portion adapted to extend into the processing machine so as to securely engage the processing machine, a head adapted for holding a blade, and a flange sandwiched between the head and the connecting portion thereby/defining a gap between the flange and a bottom face of the processing machine, the improvement including: a shoulder formed on a top face of the flange portion; an annular pad supported on the shoulder of the flange portion and adapted to be mounted around the connecting portion; and a secondary annular pad mounted on and supported by the shoulder of the flange portion, and sandwiched between the shoulder and the annular pad, whereby the gap between the flange portion and a bottom face of the processing machine is compensated for by existence of the annular pad.