I'm trying to convince myself this thing would actually be guaranteed to save my fingers but I'm failing to make the numbers come out.
10" diameter blade @ 4000 rpms = tooth tips moving at 2094" per second. SawStop says it'll stop the blade in 5ms, but that's like 10.5" of rotational movement (and 1/3 of a revolution of the blade). So on a 40T blade, that's 13 teeth passing by a point in 5ms. How would that not be enough to cut a finger clean off or at least down to the bone? I thought my math must have been faulty but even the wikipedia page for SS mentions the blade moving at 2" per millisecond, which lines up with the 10" in 5ms that I calculated.
The wikipedia page also quotes a magazine article from 2005 and says "Given the speed of the blade, it would have to stop in about 1/100 of a second - or at about an eighth of an inch of rotation after making contact. Any further, and the cut would be so deep that the device would be useless."
The "1/8 inch of rotation" being a maximum allowable amount seems pretty reasonable… but if the blade moves 2" in 1ms, then an 1/8" of movement would occur in roughly 0.06 milliseconds (60us), so how is a 5ms stop timeframe going to do anything? For that matter, them saying it needs to stop in 1/100 of a second (10ms) seems useless as well. That does not seem to correlate with 1/8" of movement in any way that I can calculate.
I feel like I'm missing something here… any other saw nerds hanging around the forums on a Saturday night? haha
ref: https://www.sawstop.com/why-sawstop/the-technology/
ref: https://en.wikipedia.org/wiki/SawStop
10" diameter blade @ 4000 rpms = tooth tips moving at 2094" per second. SawStop says it'll stop the blade in 5ms, but that's like 10.5" of rotational movement (and 1/3 of a revolution of the blade). So on a 40T blade, that's 13 teeth passing by a point in 5ms. How would that not be enough to cut a finger clean off or at least down to the bone? I thought my math must have been faulty but even the wikipedia page for SS mentions the blade moving at 2" per millisecond, which lines up with the 10" in 5ms that I calculated.
The wikipedia page also quotes a magazine article from 2005 and says "Given the speed of the blade, it would have to stop in about 1/100 of a second - or at about an eighth of an inch of rotation after making contact. Any further, and the cut would be so deep that the device would be useless."
The "1/8 inch of rotation" being a maximum allowable amount seems pretty reasonable… but if the blade moves 2" in 1ms, then an 1/8" of movement would occur in roughly 0.06 milliseconds (60us), so how is a 5ms stop timeframe going to do anything? For that matter, them saying it needs to stop in 1/100 of a second (10ms) seems useless as well. That does not seem to correlate with 1/8" of movement in any way that I can calculate.
I feel like I'm missing something here… any other saw nerds hanging around the forums on a Saturday night? haha
ref: https://www.sawstop.com/why-sawstop/the-technology/
ref: https://en.wikipedia.org/wiki/SawStop