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 . <EOS>