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Final Cut
Saving Fingers
The proof is in the hot dog.

By Harry Urban

This magazine will never endorse a material or machine. We’re here to provide an objective report on technologies that are used by secondary plastics processors. Having said that, I was floored by an invention I saw at the recent International Woodworking Fair (which also provides a technological feast for plastics fabricators).
Four entrepreneurs from Portland, Oregon displayed a safety mechanism that is capable of stopping a rotating saw blade instantly when it comes in contact with a user’s finger. Called the SawStop, it works by recognizing the difference in the electrical properties of wood (or plastics) and a user’s skin.
According to Stephen Gass, the inventor, 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 or plastics because of the relatively small inherent electrical capacitance and conductivity of the materials. 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. Once the system detects this change in the electrical signal, it 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.
Placed in the line of fire of a rotating sawblade, this hot dog was saved by the ingenious SawStop.
During the show, the invention was demonstrated by using a hot dog in place of a human finger. A large crowd gathered for each demonstration and to my knowledge it worked every time. The hot dogs that were placed in the line of fire of the sawblade received only a tiny nick. Not surprisingly, the SawStop won a coveted Challengers Award, which is given only to companies with “new, revolutionary, creative, ingenious, or forward-thinking technology, materials , services, supplies or safety devices that will advance the industry.”
Another powerful angle to this story is that Gass and his three partners are also physicists and patent attorneys to boot. Gass is also a lifelong woodworker. The partners’ credentials make me believe that the company probably has all of its bases covered. Gass said the company’s goal is to its see its safety system incorporated on every table saw sold so that the number of debilitating injuries on table saws can be dramatically reduced.
I spoke to a couple of independent “experts” at the show and neither could do anything but praise the entire concept. The technology is practical and appears to be foolproof. There is little doubt that the SawStop will save fingers and change the landscape for future saw injury litigation.
Take a look at the company’s Web site at to see a video demonstration.

Contact Harry Urban, for more information.

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