I'm actually kind of surprised that any implementation destroyed the blade. Like I don't actually care that the blade is moving, I care where the blade is moving. It seems like a trigger to yank the blade under the table would be the easier and more obvious way to do it.

A few-milliseconds yank covering up to a couple inches of blade height feels like a harder engineering problem than "trigger brakes already right near the blade to grab the shit out of the blade"

So we're somewhat lucky from an engineering standpoint. 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.

However, the blade-preserving system puts the explosive between the table and the pivot that's already there for retracting the blade. The full explosion force is there to force the blade down and it ends up being faster than the SawStop. Which while cool the SawStop was already fast enough so it's all the same.

So I don't know, I guess to me I'm surprised that the solution we jumped to first was a brake when the action of moving it out of the way takes far far less energy. It's only the energy to move the weight of the blade and bar down at the requisite speed, instead of needing to absorb the full energy of the spinning blade.

> 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.

I have had two brake activations in as many weeks, one on a dado stack (don’t ask). Neither destroyed the blade. Both blades will be back in service within a week.

Just putting out there: the popular idea that blades are always trash after an activation is not true.

That said, cheap big box store blades without carbide teeth will die a horrible death.

Carbide teeth are actually the part that gets destroyed on SawStop activations. Carbide is very brittle, so the sudden stop fractures it.

Yes, and they are consumable and replaceable by design, which goes to my point: the blade is not irreparably destroyed by the activation.

The missing teeth need to be replaced and the plate needs to be re-checked for runout, but most carbide-toothed blades are repairable.

How much does it cost to repair a carbide toothed blade, and how accessible are shops that can perform those repairs? Is it realistic that most consumers would be able to get a blade repaired rather than just running to the hardware store and getting a new one? Not being snarky; I've just never been under the impression that repairs could really be done for less than the value of a new blade.

I’m paying about $50 service fees for the two blades currently out for repair. The 10” replacements cost over $200, and the 8” dado would require buying a new stack… around $250. The same folks who sharpen and true my blades do the repairs. They’re local to me here in Maine.

Ruminating a bit:

Cheaper blades are replaced more often with use and can’t generally be sharpened; SawStop tech doesn’t change the lifetime of a blade unless an activation happens. So, if you’re already willing to run to the box store for another blade semi-regularly, whether one survives activation perhaps isn’t material?

On the other hand, somebody who doesn’t regularly use their saw is probably both more price conscious and less likely to need sharpening/replacement often. I assume they care most about whether an activation forces them to buy a new blade (and a $100 brake). I suspect those are the people who propagate “SawStop = trashed blade”. For them, it’s true.

A carbide blade costs about $100.