Lawyer’s Invention Saved 4,500 Fingers but Ate His Life

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By Martina Barash

Five years out of law school, amateur carpenter and lawyer Stephen Gass had an “Aha!” moment while fooling around in the shop next to his house.

Now, nearly 20 years later, the Consumer Product Safety Commission is proposing that his SawStop flesh-detecting and braking technology, or something like it, should be required for all table saws.

That could help reduce some of the tens of thousands of blade-related injuries that occur annually, the CPSC says.

The inventor’s story of how he came up with his finger-saving technology is, of course, one of inspiration. But it’s also one of perseverance.

And it demonstrates how Gass has needed all of his skills and training as a woodworker, physicist, and patent lawyer to overcome numerous obstacles to get to the point where he is today.

Those obstacles include bitter licensing, patent, and antitrust fights with big industry players.

While Gass and his company, SD3 LLC, are still fighting some of those cases in court, they’ve won more than than they’ve lost.

And SawStop is now so entrenched that CPSC Commissioner Joseph Mohorovic worries that a mandatory government standard would essentially hand Gass, a holder of numerous patents, a monopoly.

Gass spoke with Bloomberg BNA about how his invention came about, what he’s learned from putting his own saws on the market including in many schools, and how he sees the future of the technology. The interview has been edited for length.

Q: How did you first come up with the idea?

A: I have been a woodworker essentially my entire life. I’ve always done that as a hobby. I was out in my shop one day and looked over at my table saw, and the idea kind of came to me: I wonder if you could stop a blade fast enough that if you ran your hand into it you wouldn’t get a serious injury.

Now I also have a doctorate in physics, so I was then able to go through the analysis of what it would take, how fast would you have to stop the blade, how much force would that take, was it within the realm of possibility, was there any potentially viable system to tell the difference between cutting the wood and cutting the person.

My initial gut-check, back-of-the-envelope calculation led me to believe it was possible. I went and got a small Craftsman table saw out of the classified ads in the newspaper. And about 30 days later I had a working prototype that I could do the “hot dog demo” on. Put the hot dog on a piece of wood and cut the wood until you get to the hot dog, and the blade stops. The hot dog just has a little nick.

Q: When did you become a patent attorney? Was it before or after that?

A: I got my Ph.D. in physics in 1990 and then I went to law school. I finished in ’94 and came to Portland[, Or.] and started working full-time as a patent attorney in 1994. And I had the idea in late 1999.

Q: Did you do all the legal work behind the [SawStop] patent applications yourself, or did you hire another patent attorney?

A: I actually got a couple of my friends from work involved. I think I wrote the first one, the other guys did the second one. The founders behind SawStop were the four of us. We each contributed money and sweat equity in terms of writing the applications and doing the prototypes, building and testing, going to a trade show, all the stuff it takes to get something like this started.

Q: Do you have figures available for the volume of sales?

A: We have over 90,000 saws out in use. I think most significantly, we have well over 4,500 fingers saved—people who’ve run their hand into the blade and come out with relatively minor injuries.

Q: How do you come by that number?

A: It’s actually direct reports from customers. It’s a minimum estimate.

In our saw, the safety system is essentially incorporated in a replaceable module, what we call the brake cartridge. And if the system is activated, the brake cartridge is a disposable component that the user will replace. In addition to having the brake in it, it also has all the detection electronics and it acts as a black box and stores an electrical signature of what it looked like when the hand contacted the saw blade.

We did a couple of live tests with our fingers, very carefully. But you don’t get a sense from that of what the possible spectrum of different ways it can look. So with the data from the cartridges, we’re able to get 4,500 actual data sets of what the signal on the blade does when the teeth come into contact with the finger and work their way more deeply into the finger until the system activates.

That data is very precious to us, and very useful, but the only way we can get it is when somebody sends us a cartridge when they have a finger saved. We offer them a free replacement cartridge if they send us the spent one from a finger-save, and if they fill out a little form with some questions about the accident—and most importantly, how was the injury treated?

From that, we’re able to assess quantitatively how effective is the technology to mitigate injury. What we’ve found through reports from actual customers who’ve had the accidents is that in about 96 percent of the cases, people report that they treated their injury with a bandage or less. And the others typically were stitches.

So we’re talking, relative to the catastrophic injuries that were occurring on these saws regularly, about pretty minor consequences. That’s pretty darn close to 100 percent effective in eliminating catastrophic injury in table saws. We get cartridge and finger-save reports from customers pretty much every day now.

Q: That must be pretty gratifying.

A: There’s not many things a person can do where you get to see directly the evidence of how you’ve changed people’s lives. I got a card last fall from a mom in Chicago enclosing a picture of her high-school-age son in his baseball outfit, saying, ‘Thank you, my son got to come home from school today with all his fingers because of your saw, when he had an accident on a table saw at school.’ I don’t think I’ll do anything else in life that makes as much difference to people as this technology does.

Q: Are a lot of customers schools?

A: That’s definitely a good segment of our customer base, probably about a quarter of our customers. The accident rate in schools is certainly higher than it is elsewhere. What we see is that schools have about twice the average accident rate as the overall population of saws.

Q: Is it possible to retrofit saws with this technology?

A: From a technical standpoint it’s possible, but from an economic standpoint it’s not practical because to incorporate the braking system you have to reconfigure the internal mechanism of the saw. You have to take out the innards of the saw and replace it.

Q: With or without a mandatory rule, do you have thoughts about the future for the technology?

A: I think it’s inevitable that this kind of technology will become standard on saws because the costs of these injuries as estimated by the CPSC so vastly outweigh the costs of incorporating this technology in the saws. It’s a question of when, not if, this becomes the standard, whether it’s through CPSC or UL or market adoption and expectations.

It’s been a disappointingly long time already that it hasn’t happened and we’ve certainly tried a lot of different things to try to get the technology out there as quickly as we could. And now I can only rely on what we can do ourselves, which is develop new products and offer them to consumers. So we will continue to invest in the development of it—smaller table saws, handheld circular saws, band saws, miter saws.

Q: Is anything warming up between SawStop and other members of the industry? Do you see yourselves as the underdog?

A: At our size, I think we can’t help but be the underdog. We’re in an environment where the people we’re competing with are multi-billion-dollar international corporations and we’re a small company in Portland, Oregon, so we’re at a significant disadvantage in that regard.

Q: When you get spent cartridges returned to you, do you share your data with the CPSC?

A: We have, we’ve made that available to them as well as to UL. That’s part of what’s changed the argument a little bit. Years ago, before we had the history of the finger-saves, the industry argued from a theoretical standpoint that technology wouldn’t be effective in many accidents—people’s hands will just be going so fast that Saw Stop won’t work. But now that we have the data—with 4,500 accidents and it works every time, in cases of a kickback or a slip or otherwise—now we know there isn’t any significant doubt anymore.

Q: Any other thoughts?

A: I feel like the idea owns me more than the contrary. It’s sort of the idea that ate my life. I was in my shop and had an idea and thought, this is neat, and this’ll be great, and I’ll show it to a few saw companies, and they’ll put it on and I’ll go on with my life. Nothing could be farther from the truth.

We’re all human and one universal characteristic of humans is they’re not perfect. And using a table saw safely requires you to be perfect. We all make mistakes at times. A lot of times you get away with it, but a lot of times you don’t.

End Notes:

Gass’s company, SD3, makes its own saws—primarily heavy cast-iron or “cabinet” saws, a category that Gass says makes up about 15 percent of the table saw market.

SD3 has started to expand into the lighter “benchtop” models, which account for most of the rest of the market and which consume most of the large sawmakers’ attention.

Over the last two years, Gass and his company have racked up significant legal wins related to their SawStop technology. Among those, a federal district court in August 2016 overturned the Patent and Trademark Office’s rejection of some SawStop patents.

And, in January 2017, the International Trade Commission decided a patent infringement dispute in SD3’s favor. That ruling, against Robert Bosch Tool Corp., keeps Bosch’s products out of the U.S.

But Gass and SD3 also have suffered setbacks including in an antitrust suit filed by SD3 against major toolmakers. The trial court granted summary judgment against SD3 in October 2016. That ruling, for a second time, is currently on appeal before the U.S. Court of Appeals for the Fourth Circuit.

To contact the reporter on this story: Martina Barash in Washington at

To contact the editor responsible for this story: Steven Patrick at

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