A jig assembly for holding a mower blade and for controlling movement of a grinding tool having a grinding wheel during a sharpening operation on a cutting edge of the mower blade, said jig assembly comprising: a mast extending between a first end and a second end; a fixture portion mounted to said mast, said fixture portion including a work-supporting surface extending in a first plane and configured to receive the mower blade, a back surface of the mower blade resting on said work-supporting surface during the sharpening operation of the cutting edge of the mower blade exposed on a front surface of the mower blade; and a jig portion pivotally mounted to said mast, said jig portion comprising: an arm with a plurality of links interconnected to one another, said arm including at least a first link and a second link moveable relative to one another, said first link extending between a first end and a second end, said first end of said first link pivotally connected to said mast with a first pin, said first pin defining an arm pivot axis, said first end of said first link rectilinearly fixed relative to said mast at said first pin, said first link and said second link interconnected whereby said second link is prevented from rotating in any plane that contains the arm pivot axis, and a tool-seat disposed on said second link, the grinding wheel connected to said second link during the sharpening operation through said tool-seat. a mast extending between a first end and a second end; a fixture portion mounted to said mast, said fixture portion including a work-supporting surface extending in a first plane and configured to receive the mower blade, a back surface of the mower blade resting on said work-supporting surface during the sharpening operation of the cutting edge of the mower blade exposed on a front surface of the mower blade; and a jig portion pivotally mounted to said mast, said jig portion comprising: an arm with a plurality of links interconnected to one another, said arm including at least a first link and a second link moveable relative to one another, said first link extending between a first end and a second end, said first end of said first link pivotally connected to said mast with a first pin, said first pin defining an arm pivot axis, said first end of said first link rectilinearly fixed relative to said mast at said first pin, said first link and said second link interconnected whereby said second link is prevented from rotating in any plane that contains the arm pivot axis, and a tool-seat disposed on said second link, the grinding wheel connected to said second link during the sharpening operation through said tool-seat. an arm with a plurality of links interconnected to one another, said arm including at least a first link and a second link moveable relative to one another, said first link extending between a first end and a second end, said first end of said first link pivotally connected to said mast with a first pin, said first pin defining an arm pivot axis, said first end of said first link rectilinearly fixed relative to said mast at said first pin, said first link and said second link interconnected whereby said second link is prevented from rotating in any plane that contains the arm pivot axis, and a tool-seat disposed on said second link, the grinding wheel connected to said second link during the sharpening operation through said tool-seat.