Comment by majormajor

> Because the blade is circular the only interval of time that really matters is from detection to first movement away. Because it triggers on touch the difference between getting sawed and not is millimeters. The time from first movement to full retraction only needs to be fast on human scale time in case the person's hand is still moving into the blade. Name brand SawStop is actually fairly slow on the retraction because it uses the blade's momentum to drive it and that's plenty of speed.

Do you mean in a system with both moving it away and a break?

The only time my fingers hit the blade of a table saw they were moving with a fair amount of momentum and hit first low on the blade - dropping the blade at the speed of gravity wouldn't have been enough.

I haven't seen an explosive system like you mention - is that what Bosch had for a bit? - so I don't know just how fast that is, though dropping a spinning-towards-you blade also seems to have some other potential risks of grabbing shit with it, too. If it's fast enough I wouldn't be concerned as much, but at relatively slow speed it seems maybe nasty.