(FORTUNE Small Business) – If you were looking for someone to design a better tablesaw, Stephen Gass, 42, would be the perfect candidate. An amateur woodworker who makes home furniture in his free time, Gass also happens to be a patent attorney, and he holds a Ph.D. in physics from the University of California at San Diego. Gass, based in Portland, Ore., invented a revolutionary new tablesaw that locks whenever the blade comes into contact with human skin. Even spinning at 4,000 rpm, the blade locks in about ten milliseconds--one-30th of the blink of an eye--limiting any accidental injuries to mere scratches. (For a description of how the technology works, please see diagram.) Gass's professional model, called SawStop, went on sale in November 2004, priced at $2,500; so far about 1,000 have been sold. A hobbyist model, priced at $800, arrives on the market this summer.

The Consumer Product Safety Commission estimates that tablesaw injuries send more than 40,000 people to the emergency room each year and cause more than 3,000 accidental amputations. In 2002 the agency estimated the economic cost of those injuries at $2 billion annually, whereas the tablesaw market is only about $200 million. "I'm a woodworker, and everybody in woodworking knows somebody who's lost a finger or had an accident," says Gass.

Gass developed the product in 1999. Once he had a working prototype, he registered his patent and started getting enthusiastic responses at woodworking trade shows. But when he tried licensing the technology to tool manufacturers, they rejected the idea. He approached Delta Machinery, headquartered in Jackson, Tenn., one of the largest tablesaw manufacturers, but Gass says the company told him safety doesn't sell.

"I was flabbergasted. The industry didn't see this as a solution to a problem," says Gass. "They saw it as a problem, because it creates a product-liability issue for them." In other words, the existence of such technology could make saw manufacturers who didn't use it seem negligent. A Delta representative adds that it is an experimental system and has not been field-tested.

Critics of SawStop also told him that the saw had too many false trips, after which the $70 blade must be replaced. Gass didn't find that to be the case. Neither did Kelly Mehler, an expert woodworker and author of The Tablesaw Book, who has used a SawStop prototype in his woodworking classes for months and has reviewed the saw for several magazines.

Gass wasn't ready to give up. After being turned down by every major U.S. manufacturer, he quit practicing law to manufacture and sell his own line of tablesaws. Backed by $2 million in angel financing, Gass contracted the manufacturing to a factory in Taiwan. The first SawStop saw rolled off the assembly line last fall.

In March, Gass received a call from a company that uses SawStop, saying that it had saved the finger of an employee. Before locking, the blade scratched the skin but didn't draw blood. "It's an excellent idea, and it does work," says Mehler, who evaluates the safety of power tools for a couple of Underwriters Lab panels. "SawStop doesn't have a history yet, so it's hard to predict if there will be any bugs, but it has the potential to save a lot of fingers."