A riving knife is a tool used in woodworking that serves as a safety measure for saws. This device is positioned near a blade and moves along with the it, providing protection against cutting and kickback accidents. The shape is often that of a curved semi-circle or triangle, which tapers off at the top.
Riving knives are protective, non-rotating blades that a saw operator can affix behind the cutting blade. In this manner, any obstacles will first affect the riving knife before impacting the main blade. Riving knives are typically made of steel and are thin, but thicker than the primary blade. The width of the tools must be lesser than the width of a cut made by the primary blade, however. They also move in conjunction with the blade as they are attached to the same device as the main blade via plates and studs.
Saws are typically used to cut either across or down the length of a wood board, and dangerous accidents can occur during the process. If the wood gets stuck in the teeth of the blade, it can kick back, or be thrown backward and hit the operator. A newly-cut piece of wood may also come into contact with the blade and similarly fly out of control. At worse, any unexpected movement can make the operator lose his or her grip on the saw itself, leading to a possible hazardous cutting accident. Even a tired operator can accidentally bring a hand dangerously close to the blade.
The riving knife can help prevent all of these potential hazards. It shields the teeth of the blade and, thus, prevents wood snagging. More beneficial still, the riving knife offers an extra level of protection from the main blade for individuals due to its close positioning to the blade. As such, the device places a barrier between the moving blade and the operator's hands.
As a protective measure, the riving knife is similar to another blade tool: the splitter. A few differences mark these instruments, however. For one, a splitter should be removed from the saw while performing some procedures because its positioning far above the blade interferes with operation. A riving knife does not have such requirements, because it is affixed closer to the main blade. Further, when the blade is lowered with a splitter fixture, the splitter does not lower as well, creating a gap between the devices that could more easily facilitate wood snagging and its consequences.