Sawstop Update – Brake + Riving Knife
JeffKurtz
| Posted in Power Tools and Machinery on
Dave,
Is this the same guy who is working on the stop for band saws? A braking mechanism for a table saw is interesting, but from what I’ve read about the European models, as well as radial arm saws, most of these seem to take two seconds or more to stop the blade. (One saw in FWW’s RAS test actually took 15 seconds to come to a complete stop!) Better than nothing I suppose, but it takes only a blink of an eye to cut off a finger, making even a 2 second stop time a rather useless feature in my book.
Jeff
Replies
NO! The sawstop is not a blade braking mechanism, but an instantaneous stopping device. The typical demonstration is done with a hotdog, but it stops the blade with only a slight scratch in the surface of the 'dog. More like 2 milliseconds than 2 seconds!
Green Gables: A Contemplative Companion to Fujino Township
Norm,
Big difference! (The difference between a complete finger and a stub!)
Jeff
I've seen it (TS version). Does exactly what they say.
cabinetmaker/college instructor. Cape Breton, N.S
This might be dumb, but I personally worry less about cutting off my finger than I do about kickback. I'd think that a good splitter and bladeguard would address both issues adequately.
Pardon my dumbness, but isn't kickback one of the things that can cause one to cut off one's finger(s)? (By knocking your hand back into the blade)forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
You might be right. When I think of kickback, as I have experienced it once, it means a board flying back toward me. I personally never have my hands on the far side of the blade.
I didn't know about the saw; may get a chance to look at that website on the weekend.
As far as I'm concerned....if I was shopping for a new saw, it would be compared to all the others, and weighed. I wouldn't buy a mediocre saw just because it had a saw stop. And I don't think anyone will be rushing out to replace saws either. Administrators, I'm sure, would find it attractive; sometimes I think the only way to make them happy is to not turn the things on.
Mostly, I think the biggest part of safety is decent basic training, and a healthy respect....part of me wonders if people would get lazy thinking the gizmo was going to save them....then lazy habits become engrained. What if the gizmo doesn't work that one time? Or they move to a saw that doesn't have it? I'm becoming more convinced every day that people shouldn't be able to buy power tools without minimum training.......
I did have an accident in my shop a year and a half ago (student mangled parts of two fingers). I had just taken over the shop, and I had just done a tablesaw safety refresher, because I didn't like what I was seeing. The accident happened....in the aftermath, the class, as a group, stated that he was doing EXACTLY what I had taught them not to do (several things, actually). OHS cleared it unreservedly and quickly, because everything from their perspective was tight as a drum. My shop is in fact regarded as the safest shop in the campus. But there is a certain inherent potential danger to all the tools we use, and bad judgement is going to have consequences. I don't think a shop training people to work professionally in the industry should necessarily insulate people from that reality.
A sawstop would have lessened the damage, probably. I've seen it work. I still have some mixed feelings about the whole thing, though.
cabinetmaker/college instructor. Cape Breton, N.S
Dave-
What about false positives--those cases in which the saw stops itself because the Saw Stop thinks it has encountered a finger (but hasn't)? Do they require the same downtime for parts replacement as an actual accident? Or are false positives not a worry? My understanding of the stop mechanism is that it works sort of like the way some of my childhood acquaintances would stop someone's bicycle: by poking a baseball bat through the spokes. The safety mechanism itself causes damage to the saw. That's preferable, of course, to damaging the operator, but it is not without cost.
What is the incremental cost/benefit calculation for the Saw Stop? Fit a saw with inexpensive safety features such as a good riving knife and crown guard, then what additional advantage do you get from the Saw Stop? Is it worth $50? $500? Anything at all? I'm all for safety, but I'm also all for workers being able to continue operating their saws.
Cutting metal is the only task that would trigger a false positive.
Let's not forget hot dogs.
Hi all. I haven't been around much, but these safety conversation always draw me out of the woodwork. A couple of points:
1) I believe that kickback is the leading or at least a major cause of people cutting their fingers off. Not many folks simply put there hands into the blade.
2) Kickback can draw your fingers into the blade regardless of where you are holding the wood. It is know among expert witnesses as "human factors" analysis. Basically, human reaction time is too slow to respond correctly to kickback. As a result, your hand on the wood generally stays with the wood as it is drawn into and across the blade. (FWW has, somewhere, a good article on what kickback and how it throws the wood).
3) Push sticks help, in large part, avoid the human factor element of your hand staying with the wood. Since your hand is on the push stick and the push stick is not attached to the wood, the wood leaves the pushstick behind. The remaining problem is if you are pushing hard on the stick, your own strength may cause you to continue toward the blade.
4) The euro riving knife is an incredible leap forward for saws to be sold to the U.S. Market. Unless there has been a recent change in OSHA regs, this likely means that the saw is being marketing to shops that need not comply with OSHA.
5) Even the biggest safety nut can make a mistake. Even the biggest safety nut cannot predict the internal stresses of wood that can cause kickback. While the SawStop doesn't prevent all injury, it sure can minimize the damage.
6) Putting an invention such as the SawStop into saws does not (as some have suggested in other forums) admit the flaw in the previous design. The law is designed to prevent the use of such new inventions to prove old ones as flawed otherwise invention and progress would be stifled. Now, the use of the riving knife, that might fall into the category of something that can show an existing safety device that manufacturers did not use, though they could have, thereby raising liability issues.
Scott
Scott--
I still question the cost/benefit ratio of the SawStop.
A properly fitted riving knife and crown guard will, in my opinion, prevent nearly all kickbacks. A good guard will also prevent fingers from getting cut for other reasons. These are inexpensive solutions. The SawStop, given the other protections, is an expensive insurance against whatever potential for injury remains.
The SawStop also presents moral hazard--users might leave off other safety equipment and operate with reduced alertness in the belief that the SawStop is invincible protection. A loose analogy is automobile seat belts and air bags. Many people do not use seat belts "because the air bag will save me." Yet in most accidents where an operator or passenger is "saved" by an air bag, that person would just as effectively have been saved by the standard seat belt and shoulder harness. Seat belts are inexpensive and effective. Air bags are expensive. The cost of incremental lives saved by air bags, given the proper use of a seat belt and shoulder harness, is enormous.
All good question to which I have no answer and little opinion really. I suppose the problem in answering any of those concerns is that the U.S. is out of whack on safety standards AND allow almost no flexibility for manufactuters to experiment. If we already had riving knives and guards people used, it would be easier to asses the cost/benifit of Sawstop.
Donald.
I really don't think the cost to benefit ratio can be measured. I would assume that a person who is interested in such a device is already safety conscious, and uses guards, splitters as are available. Keep in mind, however, that certain operations such as cutting dadoes, tenons, grooves, etc. cannot be performed while most available safety equipment is mounted on the saw. Furthermore, because of these limitations, many safety conscious operates must, at times, use their saws without either a guard or splitter of any kind. (For some users, the amount of "unguarded" time is significant.) Sawstop would provide protection at these times, as well as at those times when a hand/finger slides under a guard.
One must bear in mind that most saw operators know how to cut safely. Accidents happen when the mind, or eye wanders, or laziness sets in. Nobody starts a saw planning to cut off a finger, and I bet most of us consider ourselves careful users of our equipment. Still, thousands of saw accidents resulting in thousands of amputations occur every year. I think the folks at Sawstop are doing a great service to us all.
Two final points. I lost a finger in a farm accident when I was a kid, so I guess I'll always be interested in improved safety for the workplace. As a fervent Republican/Civil Libertarian/Get Away from Me and Let Me Drink or Smoke or Eat Anything I Please American, I can foresee the day when big brother will try to force us all to have such a device. Should such a thing ever happen, and should I ever purchase a Sawstop, I shall - on that day - smash mine to bits!
Jeff
Jeff--
I thoroughly agree with all of your points (well, not the Big Brother one, because you and I are the government, and there isn't a Big Brother for us).
On cost/benefit calculations, I was really only trying to suggest that in some circumstances small incremental benefits can come at a high cost, and for many users the SawStop might have its downside and well as its benefits. Believe it or not, I really support the SawStop as an additional choice offered to saw users. Goodness knows I've been vocal enough in criticizing American saw manufacturers for not offering us a choice of effective safety devices, so I can hardly criticize someone who does make such an offer.
As a technical feat, the SawStop is very clever, and I have nothing but admiration for the inventor. I hope he makes a kazillion bucks off of it.
Perhaps I am making too much noise about a product that isn't yet available anyway. The proof will be in the pudding or the Scotch or something.
Donald,
I guess we're in agreement on almost all points, except for Big Brother. There was a mill operator up in these parts who threw the OSHA inspector off the premises. Since he had no employees, he reasoned that the presence or lack of safety devices on his equipment was none of the government's business. OSHA got a warrant, and the thing went to court. The court ruled that even though the man had no employees, he was still required to meet all OSHA regulations. The reason? If the man should sustain a debilitating injury, he would then be eligible for government benefits, thus burdening the state with his financial support.
Who's the government? No big brother? I vehemently disagree.
Jeff
funny you should mention government mandates of this technology and your strong opposition to them- if memory serves, the inventor of the sawstop is also an attorney who, after receiving the cold shoulder from the American saw mfrs, immediately ran to big brother in an attempt to force his technology upon them! (or did he just publicly threaten to? i'd have to go back and check to be certain) in any event, he apparently was not successful in this regard and has, at least temporarily, had to resort to the good old-fashioned test of the free market. i'm trying to remember where i first read about it (popular woodworking? fw?) but i clearly recall being incensed at his chicken(dung) attempt at nannyism. i'll try to do some research on this-
also, your more recent post is the first i've ever heard of osha coming down on someone with no employees- it's always been my understanding that that is test or threshold for their authority. do you have any specifics on that case?
mitch
You mentioned that the inventor or SawStop tried to cause the government to mandate the products use. Can you direct me to a source for that info? I'm interested in seeing what was tried and why.
see my post #32 above
mitch
FYI -I just exchanged emails with the Pres. of SawStop. I am going to try to confirm some of his statements independently, but have no reason to believe he lied. He said that SawStop has never lobbied OSHA or other government regulators to require SawStop or similar devices. SawStop has, however, responded to requests by OSHA and other organizations to provide information and demonstrations.
I see nothing wrong at all with responding to requests from governmental bodies and other safety organizations. Seems like good business to me. Also, it makes me reconsider some of my thoughts about OSHA and the others. Clearly, they are at least aware of new developments and actively researching them.
ok, i'm back after doing some basic checking- in volume 119- dec. '00- popular woodworking mentioned it an article on new products, then had brief updates in volumes 125- dec.'01, 126- feb. '02, and 127- apr. '02. haven't read the articles, just the abstracts on their website but i'm pretty sure that's where i would have read about it. maybe somebody has those back issues handy?
mitch
Mitch,
No documentation at this time, but I'll try to find it. Did the guy really try to bring it to Uncle Sam first? That figures. If he had the head for business that he has for science and engineering, he have gone directly to the insurance companies instead!
Jeff
Edited 10/7/2002 2:55:24 AM ET by Jeff K
The word filtering through the trade mags and the pro forums is that insurance companies are tightening up or dropping woodworking companies. And whatcha going to do without insurance?cabinetmaker/college instructor. Cape Breton, N.S
Adrian,
Watcha going to do without insurance?
Seriously? Hire a lawyer and set up a trust to protect your assetts, I guess.
Jeff
If you haven't yet looked at the Sawstop web page, do so. The thing is absolutely incredible!
Jeff
Other than the 2 seconds (literally) it takes to snap them on, seatbelts in no way impede or reduce the driving experience
But many people do not use them. They rumple my suit. They interfere with my putting on makeup. They prevent me from turning around and swatting the kids in the back seat.
As for cost, note that the riving knife addition to Sawstop's cabinet saw design adds more to the machine's cost than the blade brake.
I don't have access to the manufacturer's design and fabrication costs, so I'll have to take your word for it. Even if the device is free, there is a substantial cost (replacement blade, down time) every time it operates, whether correctly or incorrectly.
The inventor/manufacturer says there is no chance of false-positive triggering of the device. Undoubtedly he is the most morally upstanding citizen of the Western Hemisphere, but I'd still like to see some independent confirmation of that assertion.
You seem convinced that the SawStop will work flawlessly under all circumstances, so you would forego a blade guard if it came to that. I have several devices containing a microchip, capacitors, some wiring, and maybe even a spring or two. Some failed for reasons unknown, and they are sitting on my shelf staring balefully at me. But they aren't going to sever any body parts because I think they are working when they aren't.
>> ... seatbelts in no way impede or reduce the driving experience.
I take it you've never had one chew on the side of your neck throughout a long, sweaty afternoon.
The Sawstop unit is self-diagnosing every time the saw is powered up using positive feedback logic. If any component doesn't return a positive operational result then the unit will not provide current to the saw.
The ultimate safety device: A saw that can't be turned on.
This forum post is now archived. Commenting has been disabled