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How the SawStop Table Saw Blade Brake Works


A study in the Journal of Hand Surgery revealed that woodworking equipment produces over 700,000 significant injuries a year. The study also revealed that 42% of the injuries occurred with a table saw, and 37% of those injured lost one or more digits in the accident. Additionally, the survey found that approximately 40% of the injuries occurred to professional woodworkers, those who work with these types of tools on a daily basis.

Now, please don't think that I'm trying to scare anyone from taking up woodworking. However, this study shows just how easily an injury can occur, even for those professionals who are well aware of the safety rules and features of the tools they use every day. Instead, I want to bring some attention to technology that is designed to help prevent these devastating injuries.

A few years ago, a safety system was developed that detects when the blade of the table saw is touched, a blade brake is employed to stop the saw blade within milliseconds. This safety technology was introduced in table saws produced by a company called SawStop, initially in a cabinet saw, and later in a comparable contractor saw.

How does it work?

The saw blade is given an electronic signal that sensors monitor constantly. If the signal on the blade drops below a certain range, a spring-loaded aluminum block is released into the blade which stops the blade in approximately 1/200th of a second. Tests have shown that when the blade brake is employed (after contact is made with one of the blade teeth), the blade comes to a complete stop in the time it takes for two or three more teeth to make contact with the skin. This means that what could have resulted in an amputation or other devastating injury to the operator being little more than a nick on the skin.

However, SawStop's technology doesn't stop there. As the blade comes to such a violently quick stop, the force of the inertia of the blade actually causes the blade to drop beneath the table top, while the motor is simultaneously shut off.

SawStop has developed a dramatic demonstration that shows this entire electronic detection system using a hot dog (instead of a human finger). They have a video of the "Hot Dog Demo" on the SawStop web site that shows exactly how the braking system works. While the video does a great job of showing the technology, if you ever get a chance to try the demo or see it in person, it is far more impressive. I've yet to see an instance yet where members of the audience didn't shriek or gasp when it happens, because it is so startlingly quick. A look at the hot dog shows that the blade, spinning at a few thousand RPMs, barely breaks the skin of the hot dog.

Once the brake has engaged the blade, both the blade and brake will need to be replaced, but the cost of a new blade and brake are inconsequential when compared to the possible loss of a finger (or worse). Changing the brake cartridge is as simple as changing the blade, whether the brake is employed on a single blade or a stacked dado set.

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