SawStop Saws are equipped with a safety system that detects when someone accidentally contacts the spinning saw blade, and then stops the blade in milliseconds. In most cases, such an accident would result in just a nick on a SawStop saw, instead of the devastating injury which would likely occur on an ordinary saw. The video below shows what happens on a SawStop saw when a hotdog (representing a finger) hits the spinning blade at a speed of about 1 foot per second.
The SawStop safety system includes an electronic 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.
Visit the company’s Web site for more information, or check out this report from NPR’s Morning Edition.