Is it feasible to stop the blade in comparable time by reversing the motor?
CT Scans of New vs. Used SawStop
71–80 of 206 posts
Re: CT Scans of New vs. Used SawStop
#72Earlier quoted context omitted.
Actually not. My handguard saw will do as well as the sawstop non-destructively (independently tested and verified, so you don't have to take their word for it). They do it (basically) by predicting whether your hand will touch the blade, rather than waiting until it does touch the blade. If you wait until someone actually touches the blade, then yes, you have to operate very very fast. That is unavoidable due to phy…
How is that going to work reliably with sawdust and the like everywhere? Some kind of radar?
two cameras
Re: CT Scans of New vs. Used SawStop
#73Is it feasible to stop the blade in comparable time by reversing the motor?
My guess the stopping will happen in comparable time it takes to start it. So, no?
Re: CT Scans of New vs. Used SawStop
#74Re: CT Scans of New vs. Used SawStop
#75Is it feasible to stop the blade in comparable time by reversing the motor?
No, these motors usually have a very slow spin-up time (probably an induction or a DC brushed motor)
So even if you send peak current it won't (this is for the DC brushed, for the induction it can't be reversed unless you have a speed controller - also called an inverter)
Re: CT Scans of New vs. Used SawStop
#76Earlier quoted context omitted.
Yeah, see, I actually just simply don't know what the breakdown of the 30,000 incidents per year is. I would've guessed a large number of those incidents were from hobbyists and not professionals, and I would guess that the mistakes hobbyists make are different in origin from the mistakes professionals make, even if they have common threads. If it so happens that it's actually mostly professionals losing fingers, the…
I'd wager the opposite. A hobbyist will typically have a healthy fear of a table saw because one of the first things someone learns about a table saw is that it will fuck you up without a moment's notice. A pro in a hurry? Not so much. It's the pro that's gonna remove the safety guard and riving knife, be invested in expensive blades they don't want to replace if the cartridge goes off accidentally, etc., etc.
I’ve also seen many hobbyists do cuts on table saws that seem to encourage danger and then they stand right in the way too. Then they complain that “no one could have predicted this.”
The worst one I’ve seen is someone cutting circles on a table saw (already normally a no) with their hand behind the blade on the side that pulls you in instead of cutting (the kickback side). And it pulls his fingers right into the blade. (Saved by SawStop though.)
Heathy fear does not mean they know how the saw works at all. So I’d say both sides are apt to lose fingers.
Re: CT Scans of New vs. Used SawStop
#77Is it feasible to stop the blade in comparable time by reversing the motor?
Generally you want to oull the blade down, more than you want to stop it. Get it away from the finger, rather than stop it so a finger can push into it safely.
Re: CT Scans of New vs. Used SawStop
#78Mostly unrelated, but I don't think SawStop is releasing its patent anytime soon like the article states. That SawStop press release was the CEO saying they would do so if the CPSC rule was passed, but the rule wasn't voted on. And even then they were only releasing one of their hundreds of patents.
They've pretty explicitly been willing to release all of the relevant patents. The truth is it was always a red herring for their competitors. The major players all have systems that don't rely on these patents. Lawsuit discovery showed all of them had developed their own technology that was fine, patent wise. But it would have eaten into their profit. Personally, I have an altendorf handguard sliding table saw, whic…
I think free access to use the patented tech is only a part of the answer to building such a mechanism, and definitely a good first step. Looks to me like the build quality would make an even larger difference to the success of the device. For example:
> The fuse wire is designed to be stable enough to resist stretching or thinning over time despite the intense repeated vibrations from the saw use, ensuring it doesn’t prematurely release the spring.
"Just" some bad QA and the wire releasing the mechanism breaks too early needlessly destroying the saw, or too late needlessly destroying the hand. A patent won't fix that for the manufacturer.
Re: CT Scans of New vs. Used SawStop
#79Earlier quoted context omitted.
Yeah, reliably stopping a heavy very fast spinning object in just a few degrees of rotation is necessarily violent.
Actually not. My handguard saw will do as well as the sawstop non-destructively (independently tested and verified, so you don't have to take their word for it). They do it (basically) by predicting whether your hand will touch the blade, rather than waiting until it does touch the blade. If you wait until someone actually touches the blade, then yes, you have to operate very very fast. That is unavoidable due to phy…
Ive looked at the saw you mention in another comment, and in all honesty Id much rather have a safety precaution that works based on very simple physics (like sawstop) than some black-box ai hand detection algorithm.
Re: CT Scans of New vs. Used SawStop
#80Earlier quoted context omitted.
> The blade guard helps too, but AFAIK, there are many instances where you can't use it. Blade guards are rarely used in shops I've worked in. I've even worked in a shop that removed the riving knifes on their saws as they got in the way of certain cuts and they didn't want to spend time taking them on and off.
What sort of cuts would cause you to need to remove the riving knife?
Plunging cuts, and 'cove' cuts. Also smaller blades like dado stacks.
With a cove cut you move the fence to about a 30 degree angle to the blade, to get an elliptical cove along the length of a board. It's a rare thing to need. But if you really need a wide cove, it might be hard to get a router bit to do that.