SawStop makes for safer woodworking
10 Jul 2001
A US Patent Attorney has invented a device that prevents fingers being sliced off by table saws and other woodworking machinery.
Steve Gass, a keen woodworker with a Ph.D in physics, hit upon the idea to improve table saw safety in his own workshop.
'From a physics standpoint, it was really a very interesting project,' he said.
Gass realised that to make the saw blade stop quickly enough to avoid a serious injury, he would have to stop the blade in 1/100th of a second or less. He thought that stopping the blade that quickly would be possible, and he used his physics training to find a way to do it.
His experiments led to SawStop, a system that can be incorporated into table saws or other types of woodworking equipment.
The SawStop system works by recognising the difference in the electrical properties of wood and a user.
The system induces a high-frequency electrical signal on the blade of a table saw and monitors this signal for changes caused by contact between the blade and a user's body.
The signal remains unchanged when the blade cuts wood because of the relatively small inherent electrical capacitance and conductivity of wood.
However, when a user contacts the blade while the saw is operating, the electrical signal changes because of the relatively large inherent capacitance of the user's body.
The SawStop system detects this change in the electrical signal and immediately forces a brake into the teeth of the blade. The brake absorbs the energy of the blade, bringing the blade to a complete stop in approximately 2-5 milliseconds.
