Tech in Plain Sight: Table Saw Safety
If you ask around a wood shop, most people will agree that the table saw is the most dangerous tool around. There’s ample evidence that this is true. In 2015, over 30,000 ER visits happened because of table saws. However, it isn’t clear how many of those are from blade contact and how many are from other problems like kickback.
We’ve seen a hand contact a blade in a high school shop class, and the results are not pretty. We’ve heard of some people getting off lucky with stitches, reconstructive surgery, and lifelong pain. They are the lucky ones. Many people lose fingers, hands, or have permanent disfiguration and loss of function. Surgeons say that the speed and vigor of the blade means that some of the tissue around the cut vanishes, making reconstruction very difficult.
Modern Tech
These days, there are systems that can help prevent or mitigate these kinds of accidents. The most common in the United States is the patented SawStop system, which is proprietary — that is, to get it, you have to buy a saw from SawStop.
The system assumes the blade is all metal. It can detect your hand making contact with the blade, and if that happens, the saw reacts within 5 milliseconds. The system releases a beefy spring that jams an aluminum block into the saw blade, halting the 4,000 RPM rotation almost instantly. The force also moves the blade under the table. The cartridge that stops the blade and the blade won’t survive the encounter, but your finger will.
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Tear It Down!
Of course, being Hackaday, we want to see what’s inside the cartridge, and [Spag the Maker] was happy to oblige. As he points out, the sensor sometimes fires when it shouldn’t, but that’s better than not firing when it should.
In this case, the cartridge fired after contact with a metal tape measure. We’ve heard wet wood can also cause false positives. You can see the inside of the dead cartridge in the video below.
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Patents
SawStop owns several patents that prevented other similar systems from entering the market. Although many of the patents are now expired, there is one — known as the 840 patent — that is very broad and won’t expire until 2033. However, the current owners of the patent — TTS Tooltechnic — have claimed that if government regulation mandates table saws to have protection devices, they will release the patent to the public.
However, until that happens, the company continues to defend its patents vigorously. The most famous case was against Bosch, who has a competing system called Reaxx. The systems are superficially similar, but Reaxx does not destroy the blade, which only moves out of the way.
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Even this year, SawStop litigated against Felder KG, another competitor. There have been accusations that SawStop won’t reasonably license their technology, either, but we don’t know the whole story. Anyway, they’re no Volvo.
Safety First
If you don’t think a woodshop is that dangerous, have a look at “It Didn’t Have to Happen” from many years ago. This isn’t a new problem.
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The Consumer Product Safety Commission has tried to force protection systems on table saws for many years. The industry, in general, opposes them as unnecessary and expensive. The controversy is heated, with proponents pointing to the 30,000 plus injuries a year and the cost to the injured and society. The opponents talk about free markets and government interference in your shop. We won’t take sides, but having seen an injury of this type, we’ll spend our money on a safer saw even if no one is making us do it.
Then again, no one is stopping you from making your own saw with whatever safety systems you like. We’ve seen many builds based around a circular saw.