We have always been impressed with the tablesaw’s usefulness, and awed by its potential for disaster. You might say it’s a double-edged sword.
But now, carpenters and do-it-yourselfers can cut with less fear of lost limbs and digits: SawStop feels your skin and shuts off, leaving you with ‘just a flesh wound’:
The SawStop safety system includes an electronic detection system that detects when a person contacts the blade. The system induces an electrical signal onto the blade and then monitors that signal for changes. The human body has a relatively large inherent electrical capacitance and conductivity which cause the signal to drop when a person contacts the blade. Wood has a relatively small inherent capacitance and conductivity and does not cause the signal to drop…
A fast-acting brake stops the blade when contact is detected. The brake includes a heavy-duty spring to push a block of aluminum, called a brake pawl, into the teeth of the blade to stop the blade from spinning. The spring is held in compression by a fuse wire until contact is detected. When contact is detected, the system sends a surge of electricity through the fuse wire to burn the wire and release the spring. The spring pushes the brake pawl into the teeth of the spinning blade, and the teeth cut into the aluminum and bind, thereby stopping the blade. All this happens in about 3-5 milliseconds, or 1/200th of a second. At the same time, the angular momentum of the blade causes the blade to retract below the table and the power to the motor is shut off.
More from SawStop… make sure to check out the video for a demonstration.