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New Safety Feature Detects Flesh
nmb3000 writes "SawStop has introduced a new safety feature for dangerous power tools such as table and band saws which, if accurate and reliable, could result in a lot fewer people visiting the emergency room due to deadly accidents. Using the difference in electrical capacitance between various substances, the system can stop a blade rotating at 4000 RPM in less than 5 milliseconds after detecting contact with flesh. It's hard to understand just how effective this is until you see the demonstration videos where a hotdog is used in place of a potential victim's finger. The site also gives a brief explanation of how the system works as well as some high-speed videos showing just how quickly the blade stops rotating. I wonder if this same technology might be used to protect you neighbor's cat from your robotic lawnmower?"
If by "new" you mean "3 or 4 years ago"... This has shot around the internet for ever.
Sorry, this type of safety feature has been available for a few years. I have seen it demonstrated, and it is impressive. 3hp cabinet saw meets hotdog. The blade stopped instantly, with only a small nick taken out of the hot dog.
The unit I saw demonstrated was a one-use unit. Once the brake was used, it had to be replaced. The system had to be professionally installed, which is very inconvienient unless you have an installer in your city. It was also expensive, relative to the tool. However, when compared to your fingers, how expensive is it really?
Personally, I would never use one of these things. If you use your tools properly, and avoid running 'bad' wood through your tools, you will never have a problem. Avoid distractions, pay attention, and use push sticks.
(4000 / 60) = 66.66666 rps
50 teeth => 50x66.6666 = 3333.3333 tps (teeth/sec)
5 milliseconds is 5/1000 seconds, so...
3333.33333 / 1000 = 3.33333
*5 = 16.6666
So, that's 16-17 cuts, max. The blade is slowing down, and retracting, in that 5ms, so it would be even less than that.
T.
March 2003 I took a good chunk out of my left index finger on the table saw. Ouch.
And I'm normally a very, very careful person on the saw. But between a little kickback, hands in the wrong place, an odd shaped piece I wound up with an avulsion laceration (ripped the skin off the fleshy part of my fingertip about 1/8" wide and bone deep). Quick trip to the ER. Nothing really to stitch up, the doctor left it open but dressed and packed for a couple of weeks. The skin grew back, and I've got a rather odd fingerprint there now.
I'd trade what happened to my finger for the damage done to the hot dog any day.
This needs to be expanded to routers and hand tools. Kickback from circular saws is very frightening.
Get off my lawn.
lose . One "o." Say it with me: "lose."
Al Qaeda has ninjas!
That's simple ... you DO have to install a new device every time, at fairly high cost. One of the reasons most folks don't like this device.
Of course, they also don't like it because the inventor has been trying to get legal action to FORCE all manufacturers to license and install his device, because otherwise they are 'being negligent'.
The FAQ on the website says that green wood and wet wood will not trip the stop.
Of course, I don't know what other circumstances could produce a false negative - perhaps touching the side of the blade while spinning, but not the teeth?
No, I don't trust in god. He'll have to pay up front, like everybody else.
They said in the FAQ that wet wood would not cause it to misfire.
The site has several high speed videos, like this one, and from the looks of it, only one or two teeth hit the hot dog.
Man, if you were working on something and your wood got a little too wet or something, and this thing went off incorrectly, it would be both problematic and expensive. A false negative would be pretty bad too.
The features page (which has javascript rollover junk that Safari won't Grok) lists a "Metal Bypass" for cutting metalic or metal-clad stuff, that WOULD conduct enough to trigger the device.
As far as false-positive expense: I'm guessing if the total system cost is only $50-$150, then the replacement breaking cartridge couldn't be THAT expensive.
False negative would be unfortunate... I wonder how they protect themselves legally? Freak accidents could still happen, and if their magic "safety system" didn't prevent it, would people want to sue them?
- Peter
INsigNIFICANT
God, you're lazy, but this is /.
sigh.
There are no tiger attacks in my area and it's all because this rock I'm holding keeps the tigers away.