The reciprocating plunger of a power tool has a planar surface for substantial co-extensive engagement with one side of the mounting portion of plural ones of blades of varying thicknesses. A housing mounted to the plunger includes a cavity and rotatably supports a cam block in the cavity. The cam block has an arcuate cam face establishing respective plural axial lines of contact with the other side of the mounting portion of ones of the blades of varying thicknesses. Each of the lines of contact occupies an over-center relationship with respect to a plane perpendicular to the blade and containing the axis of rotation of the cam block.

The invention relates to a device for mounting a saw-blade provided with an opening to a carrier which is connected to a drive device to make a reciprocating movement, wherein the device comprises: a wall extending in the direction of movement which is suitable for contact with a side of the saw-blade; a mounting body which is rotatable opposite the wall around a shaft extending perpendicularly of the direction of movement and parallel to the wall and which is provided with a protrusion which is movable into the opening arranged in the saw-blade; and urging means for urging the mounting body to a mounting position wherein the protrusion extends into the opening arranged in the saw-blade. Mounting takes place because via the sphere the saw-blade generates a moment in clockwise direction relative to the shaft. This moment is counteracted by a moment that is generated by the friction between the actuating rod and the contact surface.

In the first embodiment, the distal end of a reciprocating plunger of a power saw includes a longitudinally extending cavity receiving a block-like wedge member. A planar wall of the cavity and a planar face of the wedge member are arranged for substantial coextensive engagement with respective opposed faces of the saw blade. A spring in the cavity engages the wedge member for urging the same outwardly of the cavity. A pin extends through the wedge and has its opposite ends received in slots in opposed walls of the plunger. These slots are inclined with respect to the longitudinal axis of the plunger and cooperate with the pin to form a cam to urge the planar surfaces into clamping engagement with the blade under the influence of the spring. The blade may be released by forcing the wedge inwardly of the cavity under finger pressure. In a second embodiment, a similar block-like wedge member cooperates with a U-shaped member mounted on the plunger. An exterior planar wall of the plunger and a planar face on the inside of the bight portion of the U-shaped member are arranged for respective coextensive engagement with opposed faces of a saw blade for holding the same in place under the influence of a spring which cooperates with cam constituted by a pin and an inclined slot in the block-like wedge member.

A fret-saw machine comprises a base unit having a table on which a workpiece to be cut is placed, a frame member disposed in the base unit and secured to the table, an arm member having one end portion secured to the frame member and another end portion disposed above the table, a blade holder assembly having first and second slide holder units and first and second blade holder units, the first slide holder unit and the first blade holder units being disposed in the base unit and secured to the frame member and the second slide holder unit and the second blade holder unit being secured to another end portion of the arm member, blade supported at its both ends by the first and second blade holder units and a drive unit supported in the base unit by the frame member and connected to the first slide holder unit to drive the blade. The blade holder unit has a blade nipping member for firmly nipping the blade. A tension applying assembly is disposed to the blade holder assembly for suitably applying the tension to the blade. The blade may carry out its reciprocal motion in an inclined manner. The arm member is fastened so as to be positionally adjustable. The fret-saw machine is further provided with a blade cover having a workpiece pressing function and a rotation preventing structure for the sake of safeness.

An apparatus is provided for attachment of a saw blade to the plunger of a jigsaw. The apparatus includes a clamping body and a clamping member which includes a lever which has an eccentric surface which bears against the saw blade. A tension spring utilizes the mechanical advantage of the lever to provide increased holding force on the saw blade.