Article on Skin sensing table saw
 

Here's a link to an interesting article about the skin sensing table saw that prevents many saw related injuries. The function is quite interesting. I can see this technology being added to many many types of machine tools to improve workshop safety substantially.

http://www.designnews.com/CA6360672.html#_self

Re: Article on Skin sensing table saw
 

Wow, if that isn't one of the most interesting and practical inventions of our time! As a young kid I can remember meeting the man who helped build my parent's house, who only had 7 fingers! This could, and should, revolutionize the business.

However, upon reading that article, I find it fascinating how the real-world market actually works. Clearly, this device has the potential to save not just fingers, but lives in the right applications; Chainsaws, hedge trimmers, lawn movers, you name it... But the manufacturers are reluctant to include it because of liability, or more importantly, their present lack of liability. Hopefully, the one law change will force manufacturers to include this technology (or similar ones) into their products.

Sawstop LLC doesn't seem to be a publicly traded company. But, if they were, I'd make sure I had some money to invest in them. It looks to be a great company, who's trying to do the right thing. Compare that to the pipeline debacle that BP is in right now... (sorry, let's please keep this thread to a discussion on Sawstop, thank!)

BEN

Re: Article on Skin sensing table saw
 

The article is interesting, and from an engineering perspective very disturbing.

If I understand it correctly, the inventor is a patent attorney with a long term hobby/interest in wood working. He decided to invent a way to stop powerfull table saws from cutting off fingers.

As an engineer, here is my problem. The inventor was not in the power tool industry. He uses power tools for his woodworking, but he is not a power tool designer.

He thought he had invented something that everyone would want, but was rejected by every company he approached.

So what did he do (here is the disturbing part): he managed to start a process to enact laws and regulations to force companys to use his invention (or something like it). This is just wrong! His 'engineering' attempt failed to get his design into production, so he turned to his lawyer friends to cram it down the industrys throat.

He has followed what engineers call the two step design cycle: Here is a problem and here is the solution. That is the human intuitive approach to solving problems, but engineers have learned over the last couple hundred years that this is not the way to do things.

If fingers getting cut off is the problem, then people who are involved in power tool design step back and study the whole problem, the whole system, the entire woodworking process, to see what leads a person to push their fingers into a saw blade.

Making a saw that will sense fingers may not be the best answer (the power tool companies seem to agree, or they would have jumped at the chance to buy his patent).

From my own experience with industrial accidents, many are caused by operators disabling the safe guards, over riding them, and then getting hurt. This system would be no different - if someone wants to bypass it, because it keeps stopping the saw for false positives, then it will be no different than other safety systems already in production.

Whats more, if people get the idea into their head that their saw will not cut them, they will get more careless, which will result in more injuries.

If someone takes a coat hanger and wires the guard on a saw blade up, its obvious to anyone that the guard is no longer over the blade. But if someone disables this stop-saw system, by cutting a wire or jumpering a sensor, another user walking up to the system will have no indication the system has been disabled.

the idea that engineers in the power tool industry care more about law suits than user safety is absurd, and down right insulting. If your invention is a good idea you dont need a plane full of lawyers to force people to implement.

Re: Article on Skin sensing table saw
 

How's this going to work if you're cutting metal?

Re: Article on Skin sensing table saw
 

Ken, I would almost agree with you. However, the power tool industry hasn't taken that step backwards to address the problem. Since they are NOT liable for people cutting their fingers off, they are NOT spending the money to solve the problem.

In the industrial world, yes, workers do bypass the existing safety systems and injure themselves. And I would assume that the push for these safety devices came from the liable companies and their insurance holders. But how many home woodworkers have safety systems similar to this? What is the percentage of injuries due to job-related vs. personal accidents? I don't know, but I can bet that the wife of the home woodworker would shell out the extra cash to have a device like this at home.

And finally, let's not forget that it's not the engineers that develop the requirements for a product. It's the sales/marketing team, along with a lot of input from those lawyers again. Bottom line, it comes down to money and liability...

BEN

Re: Article on Skin sensing table saw
 

Poorly. :p

If you're wearing gloves, and with proper attention to the design of the table surface, it might work. But who cuts metal on a table saw?

Re: Article on Skin sensing table saw
 

It's people in the power tool industry who pointed out the liability aspects if this invention were to be widely adopted. They're not engineers, they're "liability experts". You can dismiss their idea as absurd if you want, but the explanation seems entirely plausible to me.

Whether or not a flesh-sensing saw blade is the "best" answer is not important. The problem at the moment is that table saw manufacturers are not obviously taking any steps to advance the technology of user safety. SawStop has a proven technology. The only compelling reason the manufacturers give for not licensing it is economic, and I don't blame them for balking at an 8% royalty demand.

Re: Article on Skin sensing table saw
 

I dont know how proven it is. I found it interesting that they did a hot dog demonstation at a trade show at 30 minute intervals, and there was mention of a replaceable 'brake cartridge' in the system. Was there some significant cost, or down time involved, so that they only did a demo once every 30 minutes at a trade show?

I dont know the specifics of how it works, but I do know that basement inventors often design systems in a way that they work 'once', and they dont really care what it takes to get it to work again.

Do you have to replace some nail-gun-like brake cartridge every time the thing stops the blade? What is the down time after it triggers?

If Im sawing wood at 5pm on sunday afternoon, and it triggers on a damp piece of pressure treated wood, am I shut down till Sears or Home Depot opens the next morning?

If so, guess what Im going to do to my table saw?

I got a portable MPG4 video recorder and player about a year ago, that wont let you record a DVD if its copy protected. So you buy a DVD, and you want to copy it into your MPG4 player to watch it later on a trip, and you cant.

It took me about 30 seconds on Google to find out how to over-ride the copy protection system (you let the player record for 10 seconds with the input unplugged, after that it will record anything).

This will be the same deal. If someone wants to over ride it, they will. (esp after the 7th time it goes off on a damp piece of wood).

Re: Article on Skin sensing table saw
 

How many consumers want to pay the extra cost for implementation of a system like this? Before using any tool you should understand the proper operation of that tool, which includes proper safety precautions. If I cut my finger off using a power tool I suspect I will be at fault for ignoring and/or shortcutting safety procedures (guards around cutters/blades, push sticks, feather boards, anti-kickback devices ... etc ...).

How does that joke go ??
What is the difference between a Lawyer and a Catfish ? :p

Re: Article on Skin sensing table saw
 

The article mentions a fuse that gets burned up to spring the brake. I believe that this is what needs to be replaced. A task like that wouldn't be much different than an ordinary replacement fuse on a consumer product.

Re: Article on Skin sensing table saw
 

If you download the user manual, it goes into great detail about replacement of the brake system.

First, you have to understand how the brake works, then you can understand why it's a bit more complicated that just replacing a fuse or resetting a spring. The brake is basically a piece of aluminum that is forced into the teeth of the blade. When the system senses a step change in the control voltage, this curved aluminum block gets rammed into the blade. The blade embeds itself into the block and is stopped in a few milliseconds. (The slo-mo video is wild to watch...)

So, what needs to get changed? The entire brake system, which looks to be one complete module. However, since the blade is being forced into the aluminum, they recommend changing out the blade as well! So, can the blade and module be changed out in 5-10 minutes? Probably. The toughest part is probably extracting the blade from the aluminum block, nothing a block of wood and a hammer can't take care of.

So, is the extra money and the time delay worth a finger? That's up to you. Would I recommend a product like this in every school system that has a woodshop? You better believe it! A trained woodworker should have the experience and the know-how to protect himself. Unfortunately, I can't say that about most students, or even myself.

BEN

Re: Article on Skin sensing table saw
 

Ben,
You reminded me of why I posted this originally. It immediatly made me think of your former Hydrogen Source coworker who cut off 3 fingers on his table saw (all reattached). Also the number of people around our shop who are missing part or all of a finger. To me adding the price of the device up front and replacement parts is worth it no matter how careful you think you are. If the device is retro-fittable to older saws I'll be buying one for my father, an avid wood worker, asap. Otherwise he may have to wait a little longer until we get him a new saw.

Pete

Re: Article on Skin sensing table saw
 

Give me an hour and I'll bet I can come up with 5 ways to design a table saw type of machine that will prevent you from pushing your fingers into the spinning blade, and none of them will involve destroying the blade or jamming blocks of alumimun into spinning machine parts.

Re: Article on Skin sensing table saw
 

Dean Kames once said something along the lines of "Every engineering project is a solution to a problem, but not every engineering solution is something the public needs."

I believe this invention is a marvelous idea, but it just isn't practical in the real world. Once you (a company) start claiming things to be safe, all it takes is one equipment malfunction and you're really in trouble.

The problem I have with things like this is that the easier you make it for people to do something, the lesser skilled they become. I think technology like this would put power tools in the hands of people who really have no business using tools. Power tools are nto for everyone, there's no changing that fact.

I mean seriously, what are they going to do, safen every dangerous tool out there? Put a compressable sleeve over dril bits? Permanently affix a shield into a welder's head? Make an oxy-acetylene torch that you can't point at yourself?

No invention should ever replace simple diligence when it comes to using power tools.

Re: Article on Skin sensing table saw
 

A little research shows more than 50 people in the past two years who have had their digits saved, and none who have lost a finger, while using a SawStop table saw.

The manufacturers' complaint about false triggers on wet wood sounds like classic FUD. I know first-hand that a simple capacitive detector is discriminating enough by itself to tell the difference between flesh and damp plywood, and the system is additionally looking for a specific signature that indicates the blade's teeth are suddenly encountering a conductive object. You'd probably have to try cutting something like brine-soaked pine in order to force it into going off. According to the company, the system will trip if you feed it wood with greater than 40% internal moisture content -- which is something nobody should be doing. If you need to abuse the saw like that, the SawStop products have a temporary override feature that disables the brake actuator, but leaves the sensor and an indicator panel active so you can see if it would have triggered the brake on a given cut.

As for the proposal that you can prevent people from touching the blade, the same argument about subverting safety features applies. The SawStop technology is supposed to keep contact with the blade from doing major damage to a person when the usual safety procedures and equipment fail to work perfectly, whether by accident or intent. It's like an automobile's air bag, or a ground fault detecting circuit breaker.

Re: Article on Skin sensing table saw
 

But I don't think that argument should be used to naysay a safety feature. If a power tool can be made more benign when simple diligence is trumped by accidental circumstance, I consider it a good thing.

The point of inventions like this is to make systems more fail-safe. That means they're more safe when existing practices fail -- which they obviously do.

Re: Article on Skin sensing table saw
 

First-hand? I hope you still have both hands intact!

This reminds me of a classic lampoon book titled Fixit And Be Damned by Lawrence Lariar (Prentice-Hall, 1955). It contains numerous how-not-to cartoons, including one showing a guy who has just severed his hands while using a table saw. Above the saw there is a sign reading "Hands Off!"

I found the SawStop claim of "52 saves" interesting. Apparently, SawStop customers report incidents in which they were saved from injury. Other table saw users just report the injuries.

Re: Article on Skin sensing table saw
 

SawStop has a built in measure since the satisfied customers have to order a replacement for each incident. The customers without hands probably have trouble placing any orders and can't be counted.:rolleyes:

Re: Article on Skin sensing table saw
 

I built a touch-sensing light switch about thirty years ago, using a 60 Hz probe signal (instead of the much more sensitive high-frequency signal employed by SawStop). My sisters and I had fun trying to see just what would trigger it. Keys, coins, and coat hangers did. Wet wood did not. Pencil lead was hit or miss.

Re: Article on Skin sensing table saw
 

I had a TV set with a touch sensor channel selector.

Every once in a while a fly would walk across the buttons, and change the channels. I guess the fly didn't like my choice in programming.

As hard as it may be to accept, it is not possible to design power tools and powerful equipment that nobody can get hurt on (by accident). How many injuries per year are acceptable? Zero if you are the person who lost body parts.

But the reality of our lives is that we control powerful machines everyday, for some people its all day long. If you take a zero-accident approach then everything has to be very expensive, time consuming to use, with double redundant safety features. ( the ultimate system would be fully automated, you have a stack of boards and the machine saws them for you, with no human intervention - you stand outside the perimeter guards and push the start button).

Even then, if you stop a person from sawing off his fingers they may very well step in front of a bus an hour later, choke on a hot dog, fall down the stairs, get struck by lightning, or hit by a marble size meteorite (or all of the above at the same time :ahh: )

I know there is a balance to be struck. To me it seems more reasonable to find ways to keep fingers away from saw blades, than to design saw blade/finger contact systems that jam blocks of aluminum into spinning blades.

We have to accept that emergency rooms will not be put out of business anytime in our foreseeable future. We should do everything reasonable to keep people safe from harm

but everything about this system looks wrong to me. Esp the fact that it is being mandated by lawyers and elected officials, not by people who work in the industry to ensure worker safety.

Re: Article on Skin sensing table saw
 

Darn "You must spread some Reputation around before giving it to KenWittlief again."

Anyway, well said Ken.

Re: Article on Skin sensing table saw
 

I'm not sure whether the problem is with the small font size in the article or what, but you don't seem to have comprehended what it says.

Re: Article on Skin sensing table saw
 

Hard to argue with this. The inventor/petitioner is a lawyer, albeit one with a Ph.D. in Physics. I don't know if the CPSC people are elected, but they're certainly public servants -- and some of them are engineers, as Alan pointed out above..

My reservation about those opposing the petition is that parts of their argument, that safety features are expensive, inconvenient and imperfect, can be used generically against almost any safety feature.

Market forces might eventually impel adoption of safety features. Is that our standard for doing "everything reasonable to keep people safe from harm"? If so then our public servants should simply make rules requiring 'economic' safety; i.e., make us safe enough to avoid spending more on post-accident treatment than we would on pre-accident prevention. By this standard, the issue raised by the petitioners amounts to asking who should pay. Clearly the cost of treatment is paid by those who are injured or by all of us in the form of taxes, insurance premiums, etc. And if the regulations don't change, the cost of prevention will remain optional.

Re: Article on Skin sensing table saw
 

i can relate to this because i have personal experience with the said table saw. my school's shop has one and i was in the cabinet making 1 class last year. our teacher was not the least bit less concerned when we used the saw stop. usual precautions were always taken not matter what.

still, i gotta say that i somehow felt safer while using the sawstop. that quick "stop and drop" feature was like an angel over my fingers. most of the other students in my class prefered it over the old table saw we had, too. though we didn't need it, the technology and safety was more relaxing condition to work under.

Re: Article on Skin sensing table saw
 

We have one of these saws here at ULL, I was talking to the guy incharge of the shop today about it. He really likes it, esp since its more powerful than the last saw. He also said that sometimes the thing would trip if you put a metal ruler into the blade, no big deal though since its not spinning the aluminum wouldn't bond into the blade. He says its overall a really well made saw even barring the stopsaw part, he said it rarely ever kicks and whatever other things master cabinet makers like about saws.

He did say however he was having issues with certain blades not having the correct diamter so you have to be pickey with your choice, and as he said to us today,"if i can save you finger for the $70 it costs for the new cartrige i will pay it out of my pocket" for anyone having unexperienced (and overworked/undersleeped design students) using a table saw its the way to go.

Re: Article on Skin sensing table saw
 

I agree with some posters, that the issue here is whether to make such a device mandatory or not. I, for one, hate mandatory things (most of the time).

This is much like chain brakes that were developed for chain saws. In many models they are required, and in fcat they are a darned good thing to have. Certain high-end professional saws are exempted, but the people using them are usually quite experienced.

Would I retrofit this device onto my table saw? Probably not. Is it worth the money? Absolutely.

The bottom line is taht if it costs $25 million per year and saves just a single damned finger, it's worth it. Especially if that's MY finger there.

But, give me the choice.

Don

Re: Article on Skin sensing table saw
 

Ben as a college job i work at Home Depot, i worked in the Lumber Department, until..... anyone who has seen my left arm knows what comes after the until...
Let me tell you something, I will honestly admit, I made a mistake, i wasn't paying attention, and i put my arm in front of a spinning saw blade...

as a result, The Home Depot, fined my store, 200,000 dollars, because after the lawsuits and medical bills and what not, thats the approximate cost to the company, if an employee hurts is seriously injured on the job... never mind if a customer is hurt, and subsequently if you have been to home depot near the saws in the past year or 2, you probably have seen what the My store managers have affectionately refereed to as "The Schroeder Maneuver" on the Radial arm saw

Re: Article on Skin sensing table saw
 

I agree.
However, I think that pushing for legislation in order to sell your product compromises the free market economy. The best solution for this product would probably be to change it so that it can be used as a "retrofit" instead of a factory-installed-only product.
A salesman going to a school wood shop teacher with the hot dog video and a low enough price to retrofit the school saws would probably have enormous success.

It'd also be nice if the stopping solution was a bit more...innovative for lack of a better word. Destroying the blade and destroying the brake mechanism in the course of a normal deployment isn't a very good design IMO. I'm not saying that I'm prepared to present something better, I'm just saying that it shouldn't be mandatory for a table saw to eat itself. Sandrag brought up GFCI devices, which are an excellent model of an easy to reset and non self-destructive safety device. What we have now is a fuse, but we need a breaker. (To continue the electrical analogy.)

Re: Article on Skin sensing table saw
 

I agree with those who have said this should be available but not mandatory. I firmly believe that once customers begin realizing that there is a safer product available, they are fit to make the decision themselves whether it is worth it. I know if I were purchasing a table saw I would want this technology, but to each their own. Just don't ask me to pay for it when someone cuts their own finger off with their own table saw that doesn't have this technology included.

My school's wood shop just upgraded to a sawstop table saw, and as a new user most at risk of an accident with this thing, I applaud their choice. Of course, I'll be sure to stay on guard while operating the machine, sawstop or no sawstop, I feel better knowing that it's there in case of an accident.

It is true that a line between safety and efficiency has to be drawn somewhere. But for me, this technology doesn't cross or even approach that line. The only thing distinguishing this saw from any other table saw is a slightly higher initial cost; it still operates like all the others - until it hits your flesh. At that point, it may have just saved your finger. And even if in so doing it destroyed the entire apparatus, I'd consider the save worth it. I'd say a $70 easily replaceable cartridge is a good bargain for a priceless, irreplaceable finger.

Again, I'm not in favor of forcing this on anyone, but I think the technology definitely has promise.

Edit: Missed spell-check.

Re: Article on Skin sensing table saw
 

just to throw in some info I found out. I know someone in the wood working industry and saw this saw at a trade show, he said it puts on an awesome demonstration, but they don't come out and tell you it costs over $200 per catridge. I think he said it was some type of a block that gets jammed into the blade to stop it from spinning.

That is great if it saved soemone's fingers, but in a high school, i could only imagine how many times it may accidently be set off (costing $200 each time). Assuming no one is dumb enough to try it with fingers, but what about a wet towel, wet wood, food, etc...

Soudn sgreat, but from what i've heard it is a bit overpriced.

And NOTHING beats proper safety practices..

Re: Article on Skin sensing table saw
 

My company recently purchased one of these for the Carpentry Shop. They have now banned the use of non-safety table saws within the plant. The cartridge has an aluminum block shrouding the blade that is fired into the blade when activated. The torque of the motor forces the blade to withdraw into the table at the same time. This effectively ruins the blade and the cartridge needs to be replaced. Of course you can run with the safety circuit inactive, but why?

After all, what is the cost of a finger lost or having to be sewn back on? Besides the time you need it is when you least expect, most people try to work safely. This goes along with the other thread about working safely without safety glasses.

Re: Article on Skin sensing table saw
 

good question. Is the company going to make the employee pay for the new blade and the $200 cartridge everytime they touch it and it triggers?

Seems reasonable, if you trip the sensor it was your fault, and it saved your finger, right?

BTW, does it really have a SAFE / UNSAFE switch ?

Re: Article on Skin sensing table saw
 

The company does pay for the new cartridge and blade, we currently have three in stock and hope we never need one due to an injury. We assume that the employee (associate is the company term) is trying to work safe.

We keep the spares because wet wood can trip the sensor. Also any conductive material such as lexan laminated with aluminum.

It can be run inactive depending on the startup from power off. I am going from memory of the demo we had but there is a main disconnect and an on/off switch. Possibly the alternate mode is when you have non seasoned lumber and do not want to chance tripping the blade.

Re: Article on Skin sensing table saw
 

The regular brake cartridge costs $69. The one to be used with a dado blade is only $89. I don't know where the $200 figure came from -- maybe it's for a three-pack?
As mentioned before, it has a button to disable the brake actuator temporarily if you need to cut wet wood that might trip the system. The sensor circuit is still active, along with an indicator light that shows whether it would have triggered the brake.

I really don't understand your animosity toward this technology.

Re: Article on Skin sensing table saw
 

As I mentioned before, there are many ways to keep a persons fingers out of a spinning saw blade

better ways, that dont entail what amounts to jamming a monkey wrench into the system to stop it

the problem usually is that users disable the safety features, then they get hurt

so now, here we have this somewhat expensive new system, that the designer is trying to mandate into a government requirement.

That is the source of my animosity. Everything I have learned as an engineer says this whole system is not the way to go.

Also, everything I have read on the way this technology was developed says the inventor did not base his design on the real problem, because he did not work in the power tool industry, so how would he know if the leading cause of injury was equipment failure, blade failure, safety equipment being deliberately disabled by the user, or by the users supervisor, being distracted, not being able to see what you are doing...

Before you can design improvements to make a system better you must first know what the actual problems are, the root cause of failures and accidents. The designer of the MonkeyWrench Jammer was not in the loop, he did not have access, he did this on his own.

This system is a good example of what engineers call the two step, a bad design process:

1. Here is a problem (people get cut on saw blades)
2. Here is the solution (jam a hunk of metal in the blade!)

Why do people get hurt on sawblades? This product does nothing to address the root cause.

Re: Article on Skin sensing table saw
 

would you be cutting metal with a metal blade?