Comment by c22
7 months ago
You don't need to disconnect anything, you can start a saw-stop up with safety temporarily disabled using a key that comes with it. A good thing to do any time you're cutting pressure treated wood.
7 months ago
You don't need to disconnect anything, you can start a saw-stop up with safety temporarily disabled using a key that comes with it. A good thing to do any time you're cutting pressure treated wood.
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? Touch it against the blade while it's not running and see whether an LED lights up, or similar?
(I think it's unambiguously a good thing to mandate, but I'd also prefer not to have to memorize a table of materials and their interactions with the stopping device...)
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.
Most cheap lumber I see these days has a lot of moisture in it, treated or not. I’m surprised this works at all for anything short of quite-nice stock.
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If you manage to cut metal with a table saw, you are a much braver person than I am
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> 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...
What about some suggestions offered in good faith?
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Does the pressure treated wood trigger the safety device?
And is the safety device "destructive" to the saw (requires expensive parts/repair/etc to reset)?
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.
Nails alone usually won't trigger the brake. The nail would also have to be in contact with something conductive or else there's nowhere for the current to go.
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.
The brake is like $80-90 and contains a computer that collects telemetry. If it triggers for a reason other than user error you can send it in for a refund.
It doesn't drop the blade, just stops it cold (at least on the model I've used). The Bosch system dropped the blade (thereby avoiding destructive damage to the blade and brake) but they were cease-and-desisted by SawStop and unable to sell it in the US.
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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.
My dad was a machinist when he was younger. My siblings and I grew up with a well-equipped home shop, including a table saw, a drill press, a milling machine, and my dad's pride and joy: a two ton metal lathe. He drilled into us the importance of safety for all the tools, but the most vivid lesson was the story about the drill press: When he began his apprenticeship, he noticed a large photo on the wall of the shop of a long pale stringy thing. He asked what it was. It was a tendon which had been yanked out of the arm of someone whose hand got caught in a drill press. I still think about that whenever I use a drill press.
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I doubt it's amazing for the bearings, but you can replace those fairly easily(*) on most motors.
(*) for people who have a workshop, anyway
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.
But it's not destructive to the saw itself, the aluminum brake is a replaceable part.
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Pressure treated wood is electrically conductive enough for the saw to think skin is touching it