Riving knife

A gap wedge is a protective device to a circular saw. It consists of a wedge-shaped tapered upwardly curved piece of metal (usually of spring steel ) which is mounted in the cutting direction after the blade accurately in alignment with the plane fixed to the saw table. It can be vertically and horizontally adjustable to match different sheet sizes. The inner bow shall be set at a distance of 3 to 8 mm for cutting circle of the saw blade. The riving knife must be thicker than the main body and is thinner than the cutting width. The detailed rules to be laid down for example in the European standard EN1870 -1.

The riving knife prevents pinching of the blade in the kerf, which, by the lever effect the feed of the workpiece, but also by the elastic properties of the wood, particularly when sawing in the fiber direction, occur. Due to the high cutting speed would occur while a kickback of the workpiece with the risk of severe injury. In addition, the wedge prevents accidental touching of the blade from behind.

An additional protection is connected to the splitting wedge top cover, usually made ​​of a hard piece of wood with multiple width of the wedge acting as the " extension " of the wedge to the front and with a possibly ( due to high feed pressure ) but bound workpiece that retains. When sawing on a particular blade diameter according to the valid accident prevention regulations (UVV ) is a cover that covers blade and riving knife, prescribed.

Another application of the splitting wedge is in the sawmill area. There, it is used to separate parts and to prevent lateral pressure on the tool comes to subsequently can better separate and sort the two cut parts or forward.

In both cases described above is the splitting wedge from a spring steel sheet which can withstand deformation better than ordinary steels. This means that after the elastic deformation of the riving knife returns back to its starting position.