Comment by CraigRo

There are LED indicator lights that flash red when it detects a current drop. When the blade is not moving, you can touch it with your finger to see. In theory you could do this with whatever material you're going to cut. If you're cutting metal, it's pretty obvious that you need to disable the brake system. Usually where it's iffy is pressure treated lumber. Sometimes it'll trigger, sometimes not. Really depends on the moisture content of the wood and that can vary greatly. "testing" by touching the material to the blade with your hands on it might or might not indicate that the brake would fire. The points you're contacting could just not be that wet.

> Never having used one of these before, is there anything (ideally conveniently built in) that you can use to know before you cut a particular material whether it'll trigger the stop?

You use a $40 “wood moisture meter” to check the water content of the lumber before cutting. If you want a built-in one I suppose you could duct tape it to your saw.

https://www.kleintools.com/catalog/environmental-testers/pin...

Yes, anything that can conduct electricity in the wood will trigger the safety device. Pressure treated wood is often so wet with copper based preservatives that it’ll trigger the safety circuit. Old nails in wood, your finger, hand, etc will also do this.

And yes in general the blade and brake are both trashed because of the wild deacceleration forces that happen instantly. Frustrating when pressure treated wood causes this, humbling when your hand caused it.

The sawstop triggers when the blade contacts something conductive (like a finger), and needs to stop fast enough that when that happens the finger isn’t removed first.

It manages to do that within a few teeth, which is quite impressive at 1000+ RPM.

It does this by firing an explosive charge which shoves an aluminum block into the spinning blade, while dropping the blade below the level of the saw deck.

Essentially a type of airbag like braking action.

That is how it can turn s situation which would guaranteed an amputation into a minor scratch.

It can (and does) get easily triggered by things like conductive wood (pressure treated), nails or metal in the wood, metal coated plastic, etc.

Every workshop I’ve been at that has one has a collection of triggered/destroyed blades hanging on the wall.

It could undoubtably be done cheaper than it currently is ($30 a brake?) but as designed it’s destructive - and it’s hard to imagine a effective way to do what it does that isn’t destructive.

It can trigger it yes, and it is destructive to the saw blade and safety device, and can ruin the clean cut of the piece, though may or may not ruin it entirely. Good saw blades aren't cheap, and neither is the safety device. I'm unsure of what wear and tear it has on the motor itself, they can at least endure a few triggers for certain and I doubt it's "good for it" but unless you're doing it frequently I also doubt it likely to ruin the device itself but admittedly am not sure about that.

And to be clear, it's well worth it IMO. Of all the tools I have in my shop, the Table Saw is easily the most dangerous. If I had long hair the Lathe would give it a good run for it's money though. I refuse to use a table saw without a sawstop (or similar safety break). The one I have and others I've used all have a key to insert to disable the safety device If need be.

Yes its destructive. Its a gunpowder charge that forces an aluminum block into the path of the saw blade.

It works by detecting changes in capacitance so yes some treated wood and wet wood can set it off.

Pressure treated wood is electrically conductive enough for the saw to think skin is touching it

And after this change passes, the hobbyist workshop won't have a table saw at all.

Probably $9k with pretty good insurance, $17k-$20k with poor insurance (but nb the math on the good insurance probably works out such that you’re paying very close to that difference for sure every single year, in premiums)

Plus tens of hours arguing with provider billing departments and insurance. You’ll pay over what should be your max if you screw any of that up. Time lost and stress and confusion over sorting out new bills still showing up in the mail two full years after treatment was performed.

Also it’ll be a lot worse if you lose your job after.

If you don’t have insurance, you’re getting it patched up at the ER “for free” (you’ll be declaring bankruptcy soon) but not getting most of the follow-up work done. Even if your arm could be made right, it won’t be. Good luck with the nightmare of getting and maintaining disability pay-outs.

Oh and double the out of pocket costs if treatment spans two billing-years.