Abstract: A sharpener assembly for a rotating circular knife blade on a food product slicing machine has an elongate frame mounted at one of its ends for pivotal movement about an axis being substantially in the plane of the knife blade. The elongate frame has mounted for rotation thereon a grinding stone and a deburring stone. The grinding face of the grinding stone is inclined to the knife blade at an angle so as to grind a required angle on the edge of the obverse face of the knife blade. The grinding stone and the deburring stone arc mounted so that in use the obverse and reverse faces of the knife blade are respectively engaged.