When we first heard about the SawStop, we were doubtful. A table saw that actually stops when you get a finger caught in the blade? Impossible.
Well, apparently not. The SawStop induces an electrical signal onto its special blade and then monitors that signal for changes caused by contact with the human body. SawStop says:
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.
When the SawStop detects such a drop, it sends a surge of electricity through a fuse wire, which burns and releases a spring-driven block of aluminum (a “brake pawl”) into the teeth of the blade to stop it from spinning. Simultaneously, the system shuts off power to the motor and the saw’s angular momentum causes the blade to retract below the table.
The result: the blade stops in 3-5 milliseconds, turning what could have been a severed finger into just a nick.
The whole brake and fuse mechanism is contained in a cartridge which must be replaced — along with the blade — after each “emergency stop.” Pricing for the SawStop 10” cabinet saw is $2,799, and replacement cartridges run from $60 to $89. Sure, that’s not cheap, but compare it to a trip to the ER and possibly lost fingers.
There’s a lot more information about this system on the SawStop website (including a cool video of them simulating finger contact with the spinning saw using a hot dog), and we’ll definitely bring you more on this subject soon.
The SawStop Table Saw [SawStop]