A circular saw unit capable of changing an angle for cutting a workpiece comprises a base member, a rotary table which is rotatably mounted on the base member and on which the workpiece is placed, a hinge having one end supported to the rotary table and, a bracket member or support arm member pivotally connected to the other end of the hinge. The hinge comprises a lower hinge member having one end supported to the rotary table and an upper hinge member having one end pivotally connected to the other end of the lower hinge member and having the other end connected pivotally to the bracket member. The hinge may have a quadrilateral link mechanism for restricting a lower limit position of the circular saw and for assuring a horizontal movement of the circular saw during a cutting operation.

A swinging blade guard assembly for a motor driven saw blade movable from an upper at rest to a lower operational position is disclosed. An upper blade guard is fixed to a pivotally mounted supporting arm that carries the motor driven saw blade and upper blade guard. A lower swinging blade guard is pivotally mounted to the upper blade guard for fully covering the blade in its at rest position and for exposing the saw blade when moved to its operational position. The swinging blade guard assembly includes an elongated link that is pivotally attached at one end to a frame support and includes a pre-configured slot at an opposite end which receives a slidable pin attached to the lower swinging blade guard adjacent its pivotal mounting to the upper blade guard. A bearing element is also attached to the upper blade guard in laterally spaced relationship to the pin for engaging an upper surface of the elongated link. Rotation of the saw blade from an upper at rest to a lower operational position causes the bearing to press against the side of the link while also causing edge surface areas surrounding the pre-configured slot in the link to press against the pin to rotate the swinging blade guard assembly for exposure of the saw blade.

A circular sawing machine comprises a base table, a main support link having one end swingably pivoted to the base table about a first pivotal point, a support arm pivoted to the main support link to be swingable about a second pivotal point formed to the other end of the main support link, a circular saw blade mounted to the support arm to be rotatable through a rotational shaft, and a swing motion limiting link disposed between a third pivotal point formed to the base table and a fourth pivotal point formed to the support arm. The fourth pivotal point is positioned on a line connecting the second pivotal point and the rotational shaft, and a distance between the first pivotal point and the second pivotal point, a distance between the third pivotal point and the fourth pivotal point and a distance between the second pivotal point and the rotational shaft are set substantially equal to each other. A distance between the first pivotal point and the third pivotal point is set to about two times a distance between the second pivotal point and the fourth pivotal point. A support frame member is provided for the base table to be detachable to support a workpiece. A turn table is mounted rotatably to the base table.

A cutting device includes a base, a swivel seat rotatably mounted on the base and having a first end and a second end, and a blade holder releasably engaged with the second end of the swivel seat. A blade is rotatably held by the blade holder. The blade holder is pivotable relative to the swivel seat for cutting when the blade holder is engaged with the second end of the swivel seat. An inclination of the blade relative to the swivel seat is adjustable when the blade holder is disengaged from the second end of the swivel seat. An operative rod is mounted to the first end of the swivel seat and operably connected to the blade holder for controlling releasable engagement between the blade holder and the swivel seat.

A power saw is provided with a mechanism for shielding the circular saw blade of the power saw. The shielding mechanism is composed of a first shield, a second and third shield rotatable relative to said first shield, a pivot, a master connection rod, and a slave connection rod. The master connection rod is fastened with the pivot and second shield while the slave connection rod is fastened with third shield and the master connection. The second shield and third shield can be extracted to shield the circular saw blade of the power saw at such time when the circular saw blade is moved away from the work piece. The second shield and third movable shield are retracted to expose the circular saw blade at such time when the circular saw blade is moved toward the work piece.