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High-tech DIY: A finger-saving saw

Show spotlights innovations to make woodworking safer

A hot dog is used to demonstrate how sensors in the SawStop saw can detect human flesh and shut down instantly if a body part comes in contact with the blade.
A hot dog is used to demonstrate how sensors in the SawStop saw can detect human flesh and shut down instantly if a body part comes in contact with the blade.  

By Marsha Walton
CNN Sci-Tech

(CNN) -- First, there's the familiar screech of the table saw. Then a quick, loud thud. Then some startled looks among a crowd of professional woodworkers.

The center of attention is a power tool that seems to know the difference between wood and fingers, and shuts down in an instant if it senses human flesh.

"I think it's pretty cool. I could use one in my shop," said Todd Spriggins after a demonstration of SawStop at the recent International Woodworking Machinery & Furniture Supply Fair in Atlanta.

Spriggins knows firsthand a negative encounter with a table saw. He still carries a scar from an accident that took six stitches to close.

"It just happened so fast; it snatched my thumb right into the blade," Spriggins said.

"One day I was out in my shop and I looked over at my table saw and the idea just came to me," said Stephen Gass, SawStop's inventor.

Getting a charge

SawStop has an electrical charge on the saw blade. Because the human body conducts electricity, it will absorb some of the charge if it comes in contact with the blade, reducing the voltage.

Take a look  at some of the other technology highlighted at the International Woodworking Fair in Atlanta.

A sensor that monitors the voltage is designed to detect this change and to trip a brake that stops the blade within a few milliseconds.

And that, Gass said, is the difference between a Band-Aid and amputated fingers.

Early in the product development, Gass used his own fingers to test the technology and came away with just a nick, he said.

A hot dog took the place of a finger in the demonstration in Atlanta. The sensors picked up the electrical charge in the fingers holding the hot dog. When the whirring blade touched the dog, it stopped and dropped below the table, producing only a small cut on the dog.

A version of the product was unveiled two years ago at the same show. Gass, a physicist and patent attorney as well as a woodworker, thought major saw manufacturers would quickly snap up the technology. They didn't.

Manufacturers' questions

"We spent about 18 months trying to negotiate with all the power tool-making companies, trying to get them to put it on their products and they, at this point anyway, decided not to do it," said Gass.

Several major power tool manufacturers contacted by CNN would not comment on the SawStop technology, but did say their products complied with all applicable safety regulations.

Questions that critics have raised about the product include its additional cost, possible liability issues, and concern that users might become complacent about safety if they thought the machinery would somehow take care of possible dangers.

Others say that any false positives that put the brakes on the blade could be costly and time consuming.

Engineers at the U.S. Consumer Product Safety Commission tested the SawStop technology, giving the company a commendation for "innovative safety technology."

With no takers among existing saw manufacturers, Gass says SawStop has decided to build its own table saws.

Commercial and consumer models are expected to be available in the spring of 2003, at a price about 15 percent higher than saws on the market.




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