Jig for sharpening mower blades

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, the 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 pivotally connected to said mast with a first pin, said first pin defining an arm pivot axis,
• a tool-seat disposed on said arm, the grinding wheel connected to said arm during the sharpening operation through said tool-seat, and
• wherein said arm and said tool-seat are engaged with one another such that at least a first portion of said tool-seat is movable in a first rectilinear direction that includes at least a first orthogonal component that is parallel to said arm pivot axis and passes through said arm, said tool-seat further comprising a second portion fixed with said first portion during movement the first rectilinear direction, said second portion extending farther than said first portion in a direction normal to the first rectilinear direction, movement of said first portion and said second portion in the first rectilinear direction limited by a hard stop defined when said second portion directly or indirectly contacts said arm, and said first portion and said second portion are unrestrained in movement in a second rectilinear direction that is opposite to the first rectilinear direction such that said first portion and said second portion are freely separable from said arm in the second rectilinear direction.

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;
• a jig portion pivotally mounted to said mast, said jig portion comprising:
• an arm pivotally connected to said mast with a first pin, said first pin defining an arm pivot axis, and
• a tool-seat disposed on said arm, the grinding wheel connected to said arm during the sharpening operation through said tool-seat;
• wherein said fixture portion is further defined as pivotally mounted to said mast with a third pin, said third pin defining a fixture pivot axis;
• and
• wherein said fixture portion further comprises at least one stop extending above said work-support surface and limiting movement of the mower blade along said work-supporting surface, a leading edge of the mower blade resting against said at least one stop during the sharpening operation of the cutting edge of the mower blade, an intersection between the leading edge of the mower blade and said at least one stop during the sharpening operation of the cutting edge of the mower blade extending along an intersection axis, and said intersection axis and said fixture pivot axis parallel to one another, wherein said intersection axis moves about said fixture pivot axis during pivoting movement of said fixture portion, said intersection axis moving along an arcuate path in a second plane that is normal to said first plane, wherein said intersection axis and said fixture pivot axis are spaced a first distance from one another along a third axis normal to both of said intersection axis and said fixture pivot axis, wherein a third plane contains said fixture pivot axis and is normal to said arm pivot axis, wherein during the pivoting movement of said fixture portion said intersection axis moves over a range of distances from said third plane, an absolute value of a distance between endpoints of said range defining a second distance, and wherein said second distance less than one third of said first distance.