In the past there has been interest and lively discussion around the Sawstop blade brake. Let me get this out front: I have no affiliation with Sawstop. This is NOT an ad. It’s just news.
For those who aren’t familiar with the invention: Sawstop is a patented technology that senses contact between flesh and a moving saw blade, and stops the blade within several milliseconds to prevent serious injury.
Everyone agrees that a safer saw would be good. Some are concerned about the cost. Others wonder about the system’s reliability. Then there are concerns about government regulation.
Sawstop LLC has been unable to convince any current saw manufacturers to incorporate their technology. The past year or so has been spent engineering and setting up manufacturing to make their own line of saws.
So much for history. Here’s the update:
This past Friday I received a letter from Sawstop. They are apparently still bringing a Sawstop-equipped saw to market. The delivery date has shifted from Spring 2003 to Fall 2003. I’m not surprised given the engineering, contractual, shipping, distribution, etc. challenges.
Yesterday I also received an e-mail from Sawstop. They are petitioning the U. S. Consumer Product Safety Commission to require manufacturers to include something like Sawstop on table saws. Attached to the e-mail was a thorough and well rounded Word document – lots of information and a petition form at the end.
If anyone is interested, I would be happy to forward the e-mail to them. I would not like to see federal regulation used to bring a safer table saw to market, but if that’s the only way these saws can be made available then I will support the petition.
Just thought some might be interested in an update.
Regards, Dave
Replies
Please count me out! The CPSC is NOT how you get a product on the market. Come to grip with the fact that If it were a foolproof and dependable device, well tested and documented, that warranted installation on every circular saw manufactured, one or more of the big boys would have embraced it.
Manipulation of the CPSC is easy: Suzuki Samari .... tended to roll-over- certain groups wanted to ban import ... many videos and pictures of it rolling over onto outriggers ... made you cringe.... tried to pressure Government into banning import ... Government checked with Nat Highway & Transportation Dept ... no reports of death from Samari rollover ... but several hundred deaths in Ford Bronco's. oops, now we've kicked a sleeping dog! Consumer magazine fadded into the shadows, Ford redesigned Bronco into II model, then phased it out (killed it by not bidding on military contracts). There you have it - be wary.
If you must have the facts, please write all the main saw manufacturers and ask them why they have not embraced this technology. It might jack the price of a $300 saw up to $600 and then you read in the users manual that it just might not work so reliably after two years, and needs $100 of parts renewed every year to stay refreshed! While you're writing, write Sawstop and ask them for ALL the facts, and the results of the life-cycle tests they have performed.
Renew your focus on safety every minute ... think each step through ...imagine what might go wrong, and what the effect would be ... in advance of performing the task. Better to depend on the conditioned human mind than on a mechanical safety device.
Training wheels on my bicycle? don't think so! We'd still have inexpensive three wheelers if it were not for idiot or intoxicated operators. Heck, lets outlaw saws, and use lasers and waterjets! (Just kiddin' here, couldn't resist.)
Like you, I hope sawstop is for real ... however liability insurance for them won't come easy ... they will have to convince some tightfisted and savy people.
John
John,
All good points. Sawstop takes a crack at addressing them in the 10 pages that come before the petition form. I've watched Sawstop's progress since they first appeared about 3 years ago. The petition's points are entirely consistent with all informed sources I've come across - both inside (possibly slanted) and outside (apparently objective). Note the term "informed". Let me know if you want me to send you a copy of the petition. I would be interested in hearing your comments afterward.
Take Care,
Dave
Dave,
I think I'd prefer the saw making or breaking it on its own in the market place. I'm not a real fan of regulatory mandates looking out for my best interest. It always seems to really mean additional costs or expenses.
"A risk free society is a boring society."
Don
If I understand your post correctly “SawStop” is trying to force the industry to incorporate their product into the manufactures product. If this is the case I would totally disagree with this type of marketing!!! 100% DISAGREE! It also sounds like a sore loser.
I have been interested with this product and have been waiting for SawStop to bring a new saw to market. If they put out a good product then I would not mind putting out the money for the upgrade. Regardless the price as long as its within reason (up to $1000 plus the cost of the saw.) I truly believe that if this saw does as advertise and can omit the loss of limb 99 out of 100 times then they probably will make a ton of money and the other companies will gravitate towards this safety device.
The problem is that 1 out of a 100 time or 1 out of 1000 incidents when it dose not work. Better yet, false positive! If this ever makes it to the market then not just the homeowner will be buying it. All manufacture will also purchase this technology to get the insurance payment lowered.
Here lies the problem as I see it in layman’s terms. Lets say its not so much the lawsuit when one person loses his or her finger/s. What about the production shop that has false positives (situation where the saw gets jammed up with the aluminum block and shuts down production. What happens then??? Who is responsible? Who will compensate? On and on goes the list.
I hope the saw works without a hitch and may be required on all saws someday. If memory serves me correctly, seatbelts have been in cars for 40+ years and became mandatory to wear them just in the past years. Like I said, I am all for this technology but it sounds like SawStop it finding out its a lot harder to produce and get to market a decent table saw. I hope they can sell this on its own (SawStop) merit!
Regards, Lee
Edit cause I can't spell worth a dam!
Edited 3/30/2003 3:32:27 PM ET by LeeSorenson
Given the level of attention given to safety devices on tablesaws sold in this country since they've been available, I can't say I'm surprised that other manufacturers can't be bothered.
Heck, most of them (except Ryobi?!) can't even get around to using a riving knife instead of a splitter, and most of the guards on consumer tablesaws seem to exist primarily so that the manufacturer can howl "but you took off the guard" if there's an accident. (I think the SawStop saw has a riving knife, but I'm not sure.)
I'm not sure how I feel about regulation as a driver for technical improvement, but I can't say I expect improvement in this field to come any other way.
I regret that Sawstop has decided to attempt the regulation route. I doubt that they will have any success in the Bush administration, though there is a chance if they work with the labor, trial lawyer, medical, and insurance lobbies. They believe in their product, and are working hard on other avenues as well, so I understand their position. I talked about the issues with my wife for a while. She worked for many years in industrial R&D settings, and considers the strategic game being played by the saw manufacturers to be business as usual. They are stiff arming Sawstop as a matter of business strategy. Public safety is not a major issue for them. It's all about ROI, and any ripple in their pond is a threat.
I take more offense in the major saw manufacturers' snubbing of the blade brake concept than I take in Sawstop's pursuit of federal regulation. Accordingly, I signed and returned the petition.
SIMONSTL, Sawstop is working on 2 saw models. The contractor style will be just like most current contractor saws except that it will have their blade brake. The cabinet style will also have a true European riving knife design. The riving knife adds more to the saw's cost than the blade brake - on account of the complexity needed to move the arbor straight up & down instead of around a pivot like current North American cabinet saws.
The magazine for the Carpenter's Union had a brief mention of the Saw Stop tablesaws along with a photograph. (I thought I posted something about this awhile ago. I searched but couldn't find it in the archives.) I suspect the information in the article, along with the photos, would have come from a Saw Stop press release or marketing piece. As I learned from selling computer hardware and software, the hype...ooops...I mean, the marketing and advertising always come well before the actual release of the vaporware...I mean, product.
While I endorse any advancements and enhancements to the safety of our craft, I'm very suspicious of a manufacturer using a regulatory agency to wedge their way into a market. While Saw Stop is busy lobbying the CPSC, they better go on down to the Justice Department and discuss their monopoly status at the same time.
Just like at the end of Romper Room, when she held up the Magic Mirror: "I see Sherman, I see Clayton..."
tony b.
p.s. According to the CPSC web site http://www.cpsc.gov/ there are two manufacturers' recalls on power tools. A circular saw is being recalled because the blade guard sticks in the retracted position. (How many careless carpenters do you know with that funny scar on their right leg?) Also, a router is being recalled because the on/off switch may not work reliably.
Tony,
There have been challenges to Sawstop's real-life feasability. So far I haven't heard any convincing ones. The Sawstop product release delays have so far been (IMO) credibly blamed on manufacturing delays. If their Fall 2003 product release turns into Spring 2004, then even further out, one would have good reason to be skeptical.
It's not a monopoly - just ordinary use of the U.S. Patent system as it was designed to work. One part of the saw manufacturers' strategy may be to wait Sawstop out to let their patent expire. I've read the patent, and don't think it would be impossible to circumvent. The engineering is elegant, simple, and IMO entirely scalable to mass production, but I bet crafty engineers could come up with an equally good way to accomplish the same result and avoid Sawstop's 8% (on wholesale) licensing fee.
Edit: These guys have spent a lot of time thinking about the system from different viewpoints. For example, the cartridge could have been fired with an explosive charge, but they realized that explosives have legal shipping & warehousing problems. The brake is triggered by an electric surge that breaks a resistant wire instead. Simple, practical, and scalable to reality.
Regards,
Dave
Edited 3/31/2003 6:34:07 AM ET by Dave
Be careful of the laws you pass. You will be asked to enforce them. Sounds like the neighborhood spoiled brat (if you don't play with me, I'll get my mom to close the playground).
Seems to me that if this comes to pass that it would keep a lot of people from being able to enjoy the hobby we all now take for granted. I like safety, I really do, but if you make me spend an extra $300 (plus $100 a year) for something I don't want or need, just because you want to "protect" me, I just may tell you to take your invention and install it in your deep dark body cavity.
Why can't woodworkers just shoulder the responsibility for their own actions?If you amputate or maim yourself just get on with what's left of your life and admit you were just careless,stupid or both.Wrapping ones self in layers of safety equipment will only improve the odds .Living is dangerous to your health and sooner or later you will have a close call.There seems to be a paranoia about safety ,why not spend more time woodworking and less time fretting?
As soon as you, and everyone else who owns one, gives up ALL rights to sue the manufacturer for your stupidity when you cut off a finger/arm/hand, etc, then I'll agree with you.
Unfortunately, product liability costs are a ridiculous portion of the cost of most products we buy precisely because people WON'T give up that right.
In fact, if you look at, the Auto industry has been sued for:
1. Offering adjustable pedals1a.Not offering adjustable pedals
2. Offering airbags2a. Not offering airbags
Just get your signature and the signature of all other woodworkers, and I'll agree that you don't need "protecting".
d-
I understand resentment of the petition drive, but also have a problem with the manufacturers' snubbing of the concept. It's easy to disparage Sawstop's efforts if you've never been bitten, but I wonder how people who have lost fingers to their table saws feel on this issue. Any out there? Do you think Sawstop would have been a worthwhile saw component?
On your cost figures: $300 added to the table saw's cost may be accurate initially, but once patents expire and engineering solutions mature I bet it will be less than $100. As for annual costs, if you're spending $100 each year then you're tripping the mechanism and should be darn glad that your saw is so equipped.
The petition is interesting, but IMO there's no way regulations will be set in place until the device, or one similar, has already been broadly available for many years.
Take Care,
Dave
Well, I'm a stump fingered type, Dave. I lost my fingers in an agricultural machine forty years ago as an eight year old, many years before I started cabinetmaking for a living. I'm pretty handy on a key board with my stumps, ha, ha, and I like to think I can hack out a bit of furniture with them too from time to time.
Still, the mashing, and the pain at the time are indelibly burned on my mind, and the surgery, and the rehab, and the permanent weakness in my damaged hand, along with the arthritis(?) that is developing, and stiffness, and constant problems with frosty conditions since then causes me to be, at a minimum, respectful of machines, and what they can do to me, and how the problems I have hinder my working life. Guitar playing was never a serious option for me, and the deformed nails can be a bit embarrasing in company.
I'm probably one of the most safety conscious saw users that visits this forum. I use a European sliding table saw, it's the kind of saw I've always used, and I use it in what I guess is the European manner, with all the guards in place, all the time-- that eliminates from my armory such operations as using a dado blade, and cutting coves, which is no big deal-- there are many safe, effective and efficient ways for producing these joints and profiles that don't involve a table saw. Call me a woosie if you like, but I'd like to hang on to the fingers, and bits of fingers, I still have for the rest of my life, so I'll stick to using a saw the way I was trained, ha, ha.
I've watched this debate in at least two forums with interest. Funnily enough, I'm not convinced that people shoving their hands into a blade is the major source of injury around a table saw. I'd be surprised if it wasn't kickback that causes more injuries and maiming than simply sticking your fingers into the blade. Being lazy right now, I'm not going to look for definitive information and numbers.
However, I'd have to say that anything that is able to prevent an impromptu amputation or worse, is in theory a 'good idea.' Whether or not it should be added to saws by legislation I find hard to decide upon, and exactly what might the cost be, and will the customers be prepared to pay it? I wonder if the saw stop thing might fail if a blade passes up through wood at the back, and down at the front, and encounters a finger-- does it recognise a finger above the wood and stop?
What happens, as happened to someone I know, where a piece of plywood lifted up at the back into a pre-kickback situation. This girls reaction was to slam down on the ply, and as the ply was sliced open by the blade, her fingers, above the ply got caught by the blade as it emerged on the top side. She let go then, and the plywood flew across the room. Well, even as a maimed woodworker, I'm just not sure about this device----yet, so I can't decide if I'm in favour of it or not. Anyone got any persuasive arguments? Slainte.Website The poster formerly known as Sgian Dubh.
Thanks for posting! You always bring perspective to threads. Sawstop stops the blade whenever it touches flesh - no matter where or how. Regards.
I don't have a problem with the Saw Stop being available. What I do have a problem with is the fact that they want the Government to require every saw made to have one. This after they cried that the present saw manufactures would not buy their patent and they can't get their saw on the market.
What it boils down to is the fact that they can't compete on level ground so they want the liberals to force us to buy something we may or may not want.
They say that in order to keep SS at it's peak working condition you should replace the cartridge every year even if it has not tripped. Cost of this replacement will be whatever they deem reasonable and proper. It WILL be more than $5.
If you want to buy a Saw Stop then go ahead. Heck, I might even buy one, maybe two. Just don't "require" me to buy something that is not proven. A hundred trips on a hot dog doesn't make it a good thing.
This is the first I've heard of the cartridge needing to be replaced on any sort of regular basis. I have heard that the unit runs a self diagnostic every time the saw is turned on, and will not fire up if everything doesn't check out correctly. My impression is that startup failures would be very rare. Where did you pick up the annual replacement data? Was it from a reputable source - preferably Sawstop themselves?
BTW, I noticed that the full petition text (and photos) is on their website now - http://www.sawstop.com/. It's an interesting read. They cover a lot of history, some accident statistics, economics, and the technology itself.
Regards,
Dave
I've read the petition. It's certainly self-serving, isn't it? No mention of other devices that would improve safety--riving knife, blade guard, that sort of thing--the other dangers noted by Richard. Just a naked appeal for government intervention in the market. Despite their emotional rhetoric and the way-over-the-top emotionalism of the pictures, the petition itself makes clear that their concern is the economic welfare of the three primary petitioners, not the overall safety of woodworkers.
For all I know, it is a useful device. Their estimate of adding 25% to the cost of a saw seems outlandish to me.
Why not circulate a petition to have the US taxpayers pay each of them a bunch of money each year. That's not far from what they are asking.
Edited 4/2/2003 9:30:59 PM ET by Donald C. Brown
Maybe they should have hidden the blade brake deep inside a petition to require a dozen safety features. That would have been less honest and the eventual regulation (not that I think there's any risk of there being one anytime soon) would somehow drop several of the features, including the blade brake, and instead add a requirement for all table saws to have an integral breathalyzer to prevent startup unless you are sober. Maybe they would just do away with table saws altogether.
Maybe. Still, I think naked self interest, not a concern for saw users' safety, is starkly clear from the wording of their petition.
I said else where and I'll say it again
KEEP THE GOVERNEMENT OUT OF MY LIFE.
Life is risk.
stay in bed if you don't want to get hurt
I agree.
I may be incorrect but if the goverment mandates this feature wouldn't sawstop have to give up their patents? Allowing all saw manufacturers to produce it.
After reading their petition, it really seems like they are being entirely self serving.
"Sawstop stops the blade whenever it touches flesh - no matter where or how."
Just curious, exactly what triggers this thing? If it is electrical resistance/impedance or something along those lines, wouldn't a wet piece of lumber of the right density shut the saw down mid cut? How does it differentiate between fingers, hotdogs, and wood?
Jon
Jon,
I'll try a somewhat brief description of how Sawstop senses flesh contact. They pass a low voltage electrical charge to the blade. When anything that conducts electricity touches the blade the voltage drops momentarily as power is drawn into the new object. Sawstop's electronics sense and "graph" this voltage drop and the following recovery. This all happens in 1 or 2 thousandths of a second. It turns out that the shape of this "graph" for human flesh is different from wood of any moisture content and physical size.
Dave
Dave,
Your explanation of how it works doesn't sound all that high tech. They were able to patent that? Sounds to me like a crude takeoff of an IC engine fuel and ignition management system, but instead of being applied to something as complex, it was adapted to a table saw. Do you know if a patent be revoked?
Jon
The patent, at least the one I've seen (there may be multiple patents), is for the whole assembly. It goes into how the sensor works, but I don't recall if that is the unique and patentable aspect of the assembly. Dave
Dave,
Back to what other's seem to be saying. If it is so great an idea, how come it has to be legislated (forced) on us.
The overall concept is good, but their tactics and strategy (based exclusively on what I've read here) seem more self serving, than serving the overall public interest. Any modern tool shop (and there are thousands in the U.S.) could design and build such a product without a lot of effort.
Are the costs to society of not have self-stopping machine tools (can't stop with just table saws [pardon the pun]) so great that we need it to be legislated? Personally, I think not.
Jon
I have one friend who lost a finger in a high school woodshop class. My neighbor three houses away, a full time cabinet maker with 0ver 30 years experience cut off two fingers and a thumb, they were reattached. He lost twenty weeks work and is pain when ever the temperature drops below forty degees. I was in his shop last week, he has NO guard on his radial arm saw, and nothing on his table saw except a 1/16" drill bit sticking up and acting as a splitter. He says hes to old to change now. He's sixty eight. He estimated it cost him fifthy grand in lost business, over 100,000 on medical. A custimor of mine worked for a company that manufactured largue lenses for telescopes, the Hubble. he built the wooden cradles used for the grinding of the glass blanks. He lost several fingers, they were reattached. He couldn't work for a year. he told me that the guy he replaced or the guy that replaced him also had lost part of his hand. This thread prompted me to call the two local schools that have wood programs, when I explained what might be available in the future for a saw safety device (as I explained to them)That would stop the blade before the fingers, they were very excited. Both schools said they would like to purchase one now. As a taxpayer I would want my area kids protected to the best of their ability to do so. The school insurance would likely, insist on this device. Thirty years ago how many wore safety glasses, or dust masks? In all the above cases the tax payer picked up some of the costs. Insurance didn't cover every thing. My thoughts are that SawStop corp. ship a saw to every magazine for a tool review. Do every w.w. show, A quality saw with safety built in for a few hundres bucks is a no brainer. When other saw componies sales are effected, then you'll see them every ware. Safety costs money, but accidents cost more. Just my thoughts, Ron
Thanks for sharing some real world injury costs, Ron. I think there is enormous pent up demand for a blade brake, whether by Sawstop or anyone else. Existing saw manufacturers could have had versions on the market within 12 months of deciding to do it. Instead, they decided to force Sawstop to go through the entire engineering/staffing/manufacturing/design/distribution/service sequence. These sequences aren't trivial or predictable. The end result is that these saws are taking about 2 years longer to get to market than if an existing manufacturer had jumped on board. 2 years. Long enough for about 60,000 ER visits, including 6,000 for amputations, in the US alone.
I'm not sure why Sawstop decided to circulate the petition. Maybe it was really to solidify their existing preorder base, which I understand to be significant. They understand that the saws must be good saws on performance issues, and be well backed up on support & parts. The cartridges in particular, will probably be a quick ship Fed-X item.
I bet the saw manufacturers are watching this very closely. If Sawstop's launch starts strongly and shows long term durability, some of them will probably offer versions within a year or 2.
Each shop has to make their own decisions regarding a blade brake saw. I am by far the heaviest user of my table saw, but other people use it too. Sometimes a neighbor needs some wood cut. Every now and then a coworker uses my shop to build a wood project model. My scouts (I'm a den leader) will be old enough to use the shop in a few years. I can't trust these people to have the knowledge and vigilence to use my saw with the same safety that I do. I know...the best approach may be to simply refuse them shop access. I choose carefully who I allow in, but one never knows. I should probably touch base with a lawyer about how to indemnify myself in these instances.
Regards, Dave
Dave,
"I think there is enormous pent up demand for a blade brake, whether by Sawstop or anyone else."
I couldn't agree with you more. Just question why they [the Sawstop people] have chosen the marketing route that they have. Only available on new saws (no retrofits) and to force it through legislation. Makes me wonder. Anyone else? For about 1/10 of what they stand to make on this, I bet my company could come up with a retrofitable device that stops a blade in an instant.
Jon
Jon,
Steve Gass has told me that the device cannot be retrofit to existing saws. I didn't pursue the line of questioning further, but think it has to do with not enough space available in the cabinet, needing much larger arbor bearings, electrically isolating the blade, and designing the arbor to snap loose from the trunnion and drop below the table. Include installation hassle and expense, and the blizzard of versions needed for existing saw variations, and the retrofit would cost more than a new saw. If it wasn't done correctly the device might not fire up at all or might not trip properly.
The point is a very good one, though. Your company? Ask them to look into the possibility.
Regards, Dave
Dave, thanks for you input. I think that several inventors that I know never wanted any out side money to control their dream idea. They got their inventions to market and several of them became very well off. The deal with the Con.Pro.Saf.Comm. is really brilliant. A very inexpensive way to get national attention. They probably spent very little and received quite a lot. Ron
My understanding is it works on the same principle as "touch lamps" -- that made it easy for my physics-challenged mind to undestand <g>.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
What it boils down to is the fact that they can't compete on level ground so they want the liberals to force us to buy something we may or may not want.
It is generally a conservative view that people aren't smart enough to know what is good for them and need the government to decide that for them. The liberals just want the government to give them our money but not tell them how to spend it.
TDF
I have been injured on a table saw. Both times, sawstop would not have made a difference in how i was injured. The first time, I was hit with a .5"x12"x18" oak board that kicked back on me during a rabbet cut. The second time, I cut off the end of my finger trying to move a strip of pine past the splitter. Neither of these were good experiences for a freshmen in high school woodshop, and neither of these could have been prevented or made less harmful by sawstop.
There are a lot of ways to make cutting on the table saw safer without saw stop. Splitters, pushsticks, blade guards, common sense, they all make cutting on a table saw a lot safer. Saw stop isn't needed, and they're attempt to force the major saw companies to install their product using the government is just wrong. When I finally save up enough money to buy my own table saw, I don't want to have to wait another 6 months to pay for a device that won't work 100% of the time or won't even be needed as long as i'm using my head while I work.
If the manufacturers are going to put some time and money into safety improvements, I'd much rather see them start with a decent riving knife and anti-kickback system in a package with a guard, all of which should be easily removed or otherwise put out of the way for work with dado blades, etc.
The lack of these features is my absolute biggest gripe about saws.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
"Sawstop LLC has been unable to convince any current saw manufacturers to incorporate their technology. The past year or so has been spent engineering and setting up manufacturing to make their own line of saws."
To the first sentence, perhaps it's their strategy and tactics vis-a-vie royalties and restrictions that are impeding their progress with major saw manufacturers. It's surely not an aversion to safety; even the European mfgs who are encumbered by regulations in this area have not licensed the Sawstop technology. The point is that you can't force a company to incorporate something specific like this, you can regulate the area of workplace safety, but our government has spent years undoing legislated monopolies so the idea of legislating a specific companys technology is pretty remote.
The second sentence is right on, if they have superior technology then put it in the market and let the consumer determine it's value. I hope they are successful in their product launch, it will entice other manufacturers to dedicate more resources to this area.
Jeff, I could not agree more with you!!!
I very much so hope that they are able to get it all together and produce a safe and FINE product. The caveat here is they need to produce a nice saw as well. I don't believe that anyone will buy a saw that cant cut straight even with all the safety features... Well, most of us wouldn’t!!!
Lee
some days I can't cut straight no matter what saw I'm using... so I need all the help I can get in this area!
Mark, Toby's right. Sawstop would have made your blade contact a shallow nick instead of an amputation. In about 0.005 second it stops the blade cold AND drops it below the table.
Edit: I imagine that the blade brake's action, being so quick and powerful (150 HP instaneous force applied to the blade), is quite loud and startling. The operator's first thought will probably be along the lines of "C__p! The sawstop just misfired - ruining my workday and costing me a bunch of money!" Sometime later on the operator will notice the nick on his or her hand.
FG, I'm with you. The Sawstop model that would interest me is their cabinet saw that has a riving knife. I don't have data on the final design, but think it will have anti-kickback pawls and a guard as well. The riving knife, of course, will not have to be removed regularly. I will be interested in seeing how easy they make it to remove the pawls and guard. Mounting a dado blade won't be as easy as with a conventional saw. The riving knife will extend above it. The blade brake cartridge will have to be switched to one designed for the dado blade's diameter. That sounds like enough hassle to head me in the direction of the router table instead.
Dave
Edited 4/3/2003 10:42:18 PM ET by Dave
If they're as clever as the Beisemeyer people (or use their knife and pay a bit), the knife will just push down out of the way. Anyone know what the Sawstop saw is going to be a clone of? We're always hearing tales about how Saw A must be the same as Saw B, because they come out of the same factory or have the same paint job or whatever! LOL.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
After a couple hours strolling around my first large woodworking machine show I noticed the pattern. Many of the machines were obviously made at the same factory. Same casting details.
The saws that appear on the Sawstop site are, of course, actually Powermatic saws with a paint job. The pictures were taken before engineering had been completed on the Sawstop saws, let alone any preproduction versions.
I've heard that the saws, and I agree that Sawstop's best long term shot is to focus on getting the saws to market, will be made at Mao Shan - the same company who manufacturers Jet and overseas Powermatic. They will be similar in appearance to conventional saws, but will have completely different internals. Working that all out is probably the delay.
Additional space is needed for the electronics and brake. The arbor bearings are massive, even larger on the contractor version than a PM66, to take the blade brake force without damage. The cabinet saw arbor will move straight up and down on dovetail ways like many European saws.
Dave,
I gott say it. You sound suspiciously like a shill for Sawstop. You sure seem to know a lot of mundane facts about the company. Maybe it's just my suspicious nature, but it sure seems that way to me. And no, I wouldn't be surprised if a company that tries to sell it's product through legislation would stoop to putting a ringer on a forum.
Check the message with which I started this thread. No paid affiliation with Sawstop. I find the technology interesting, and the potential valuable. There is a lot of misinformation out about the invention. I don't mind helping correct some of it.
I have picked up the mundane facts by remembering articles I've come across about it, reading a few lengthy threads in which Steve Gass (the inventor) participated, and trading e-mails with Steve Gass. It doesn't sound that way, but I am actually as skeptical as anyone here. Questions have come to mind. Instead of speculating or making up an answer, I've simply written Steve Gass an e-mail. He replies quicky, and apparently personally, with clear and well-reasoned answers.
So far I haven't come across any evidence of deceptive or unethical practices on Sawstop's part. You may not endorse their actions, but they are not trying to fool anyone.
If you doubt my words, please visit the Knots Archives and look for posts from Dave Wright. The software here has made me reregister a few times. The name might have shifted around a bit (Dave, Dave Wright, Dave_Wright), but I've been posting here on a wide range of topics for about the last 4 years. I haven't posted much in the last few months on account being busy with a new job. Look earlier. I'm in the minority - people who post with their actual names instead of handles.
Regards,
Dave
In that case, I apologize. Part of my suspicisions were the lack of previoius posts. Thanks for setting me straight.
Edited 4/5/2003 3:51:43 PM ET by BDW13
Cher Fan,
Yes, the Saw Stop cabinet saw will be another clone. According to the SS web site the machine will be built in Taiwan by Mao Shan.
Jeff
Jeff, I saw that info in an earlier post. It doesn't tell me, though, which currently available saw I can reference it to. What other saws are produced in that factory?forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
I know Jet is made there, and I believe Grizzly is also as well as some Delta. Part of the problem with comparing to other products made there is that although they may look the same, differences in casting quality (thickness, alloy, etc.) and machining tolerances will vary according to the specifications of each customer.
Guess that's not an uncommon thing in manufacturing facilities. When my dad was a machinist at International Harvester, they made engine blocks not only for their own products, but for other companies as well. Most were very good products, with the notable exception of the blocks they made for American Motors which were often machined before they were even completely cooled. Is it any wonder why those old Ramblers burned oil?
Jeff
Edited 4/11/2003 11:58:49 PM ET by Jeff K
FG,
You will not be able to reference the Sawstop saw to any other manufacturer's model. It will be made in a factory that makes other table saws, yes, but it will not share parts with those saws. The nearby BMW plant makes sports cars and SUVs...same thing...they're both vehicles but one is not a knockoff of the other. The "Powermatic" saw being demoed by Sawstop is a good example. It has an OEM Powermatic cast iron top and sheet metal cabinet, but the guts had to be completely ripped out to make room for the Sawstop guts.
The closest you will come is to cross a Jet cabinet saw (same manufacturer), INCA 12" cabinet saw (riving knife, vertical arbor travel, massive arbor), and the antilock brakes and airbag from a sports car.
Dave
OK, great!!!! I'm going to reference your's and Jeff's responses to my question the next time someone goes on one of these rants about how this saw is like that saw, which is just like that saw, because they're all made in the same factory.
I've always thought that line of logic was full of holes.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
>The second time, I cut off the end of my finger trying to move a strip of pine past the splitter.
Yes, I touched the blade, for a split second. I didn't even know it was cut until it jerked away from the table. By the time sawstop would have kicked in, my bloody finger had already kicked away by the blade. It was only a nick. I was too concerned about it. It didn't really hurt until the nurse put betadine on it. But my shop teacher was flippin out.
The sawstop cannot prevent stupidity.
I was also in a rush that day and wasn't doing thing safely. My teacher spends a better part of the first semester working just on safety. If I hadn't been rushing and paying more attention to what I was doing, it wouldn't have happened.
Our school has enough money each year to pay for about 500 bf of pine and usually enough left over to repair a motor or to but a new miter saw (we finally got a really nice one too). But our school has nowhere near enough money to buy a new table saw, especially one with a 300 or 500 dollar saw stop on it.
Edited 4/3/2003 10:02:48 PM ET by Mark
This reminds me of the "smart gun" story. Make guns smart so that only their owner can use them. Now, given that over 50% of the police who were killed by guns were shot by their own weapon, you'd think the police would embrace this technology. But, it turns out, they are exempted from having to use "smart weapons" in places where there has been legislation to make them the only guns sold (eg Maryland).
If they have a product that is better, then let them demonstrate it in the marketplace.
The reality is that you can't make anything idiot proof, because someone will just invent a better idiot.
Take antilock brakes. Turns out that cars equipped with antilock brakes are involved in just as many accidents as regular cars. Why? Well, it seems thoe drivers of ABS cars feel more in control and immune, so they tend to drive 5-10 mph faster. So in reality, any advance in technology is quickly compensated for by a change in behavior.
Look a 4WD vehicles, same thing. People feel immune until they discover a 4WD vehicle generally has no better stopping ability than a regular car with snow tires. The road from Portland to Mt Hood is lined with crosses and flowers dedicated to people who thought that a 4WD vehicle was the end all in safety.
I subscribe to what Click and Clack suggest for a perfect auto for a teenage boy. Put a big pointed stick on the steering wheel. Trust me, that teenager will be a much better driver because he *will* be paying attention.
Same goes for tablesaw operators. Give them a sense that things are completely safe, and the whole attitude of shop safety starts to crumble. You'll find that just as many accidents occur because people are acting much less safely overall. Most accidents occur because safety guidelines were ignored or safety equipment was removed. How long until the Sawstop system is disconnected because it keeps stopping the saw with every blip in the power supply line.
You just can't legislate common sense, and unfortunately, we are becoming a society dominated by people who think someone else has to be responsible for when they screw up. We need to get back to a society where people understand that when they buy the ticket, they take the ride. I have no problem with this company developing and marketing the saw, but I do have a problem with them legislating it. Also, I am a PhD medical scientist with a pretty good understanding of mechanical systems. I am very skeptical that this one would work. In fact, my BS bell started ringing immediately. Remember, you aren't just dealing with the momentum of the blade, but also the motor and the drive system. Now, in order to build a system that can withstand the stresses and forces of the braking system, you have to beef up the arbor, pulleys, and bearings, which means even more rotating mass that has to be stopped. Then you have all the issues of sensing an electrical current through human tissue. Quite frankly, I'm surprised that this has even gotten past Consumer Product Safety and FDA on those grounds. Sorry, but too many things here just don't add up for me.
If it is so wonderful, then why hasn't sawstop taken it on the road with the woodworking shows already? One saw could have gone to 20 shows last year, and we wouldn't be having this discussion. Me thinks that once people see the prototype, any interest in the saw will fade.
MW,
You have some interesting opinions on this issue. Our physical world is filled with safety features. Funny how the controversy around today's new safety features is forgotten tomorrow. Guardrails on stairs, plastic dashboards in cars instead of metal, sprinkler systems in most public buildings, kickback prevention on chain saws, ground fault interrupt outlets, etc.; the list is enormous. Each of these innovations had their share of skeptics and complainers. No one questions them today. We just blithely go about our lives, every now and then being saved from injury or death without feeling the least bit thankful for the effort it took to make them part of our world.
As for Sawstop making people lazy... temporarily losing the use of my saw and having to spend $100 - $150 to get it back running ($60 cartridge plus new blade) is a fair amount of incentive to stay safe. I'm not fond of 1/16" deep nicks taken out of my fingers either.
With all respect to your educational and professional credentials, the technology is possible if not eminently practical.
Now, in order to build a system that can withstand the stresses and forces of the braking system, you have to beef up the arbor, pulleys, and bearings, which means even more rotating mass that has to be stopped.
The Sawstop saw does have beefed up internals. The rotating mass actually works in Sawstop's favor. The brake has self-energizing geometry. The saw's own force pulls the brake into the blade's teeth. The blade dropping below the table actually reduces forces on the system.
If it is so wonderful, then why hasn't sawstop taken it on the road with the woodworking shows already?
Sawstop made a few prototypes. They have been demonstrated at several major woodworking shows every year since 2000. Many people have watched them work, and gone away believing in the technology and anticipating the time when they will be available to the general public.
The companies that have studied a prototype SawStop saw are: Black & Decker (Black & Decker and DeWalt brands), Ryobi (Craftsman and Ryobi brands), S-B Power Tool Co. (Skil and Bosch brands), Emerson (Ridgid brand), WMH Tool Group (Jet and Powermatic brands), Hilti (Hilti brand), and Rexon (Craftsman and Tradesman brands). Other companies that have studied the technology or various components of the SawStop system include Delta Machinery (Delta and Porter Cable brands) and Makita (Makita brand). Engineers from these companies have questioned details of the device, such as its dust resistance and ability to differentiate flesh from wet wood, but none of them have found fault in the basic sensing and braking technology.
I think Sawstop is not available yet because they started with very small staffing and assumed that the best path to market would be through existing manufacturers. No such luck. All the big boys want to watch from the sidelines.
Regards,
Dave
"I think Sawstop is not available yet because they started with very small staffing and assumed that the best path to market would be through existing manufacturers. No such luck. All the big boys want to watch from the sidelines."
Dave ,
I commend you for your efforts to educate us all as to to the benefits of a table saw blade brake. But after reading through every post here, watching their [the SawStop] video clip, reading the petition...etc...etc.., and understanding how SawStop actually works, I have to say that now I understand why they [the SawStop people] are taking the route that they are, and why all the major saw mfr.'s are sticking to the sidelines.
While I don't think that their design is flawed per say. From an engineering standpoint, too many concessions seem to have been made in its design. One is the need for the blade to retract below the table. Another, based on the brake design, is that it seems like it would not be real compatible with the wide variety of blade diameters, dado blades, and moulding cutters, typically used on an individual saw.
Again, in concept, it's a great idea. But the engineering behind how that idea was executed? Definitely needs, well,... a different approach. But I guess it's easier to lobby for legislation than to make the product better.
Jon
"why all the major saw mfr.'s are sticking to the sidelines."
Yeah. Re-design costs them money, and money is more exciting than a safer product. Heck, they haven't even gotten around to a riving knife in the last fifty years, except for Ryobi.
It doesn't sound like there's an engineering problem in SawStop. It sounds like there's a budget problem in re-engineering for it.
Simon,
Wouldn't it have made more sense for the people at SawStop to engineer a device that is easily adaptable to the majority of saw mfr's current designs, or even better, the 1,000,000's of tablesaws in workshops throughout this land?
The reason for lack of interest is that their design needs some major refinement. Personally, I'd gladly fess up a few hundred $ for a retrofit for my table saw (or for that matter, blade stops for all my equipment). But currently, nobody seems to be addressing that issue.
For the SawStop people to try the legislative route, and try to force all the tablesaw makers to redesign their products around the SawStop's spec's just doesn't seem like the best way to get a tablesaw brake on the majority of saws that will be out in the field for the next few generations.
Jon
Actually, reading through the design has made me more skeptical. Rather than touring the woodworking shows with a "one-of" demo model, they will need to show how well production machines work, not $100,000 hand built prototypes.
Lets say that Sawstop gets their wish and legislation is re-written so that all new saws have to incorporate their design. You know what you are going to see? A big boom in used saws, and used saw parts. Because believe it or not, people are generally skeptical about stuff that is forced down their throats. Most people, like me, really want to see a history behind a product before they go out and drop money on it. All the things you cited weren't just legislated into existence. Auto manufacturers provided safety devices before they were legislated into place to ensure they were in all automobiles. They had a proven track record and were commercially available before their use became mandatory. The fact that they are going legislative the sawstop first tells me that this idea isn't going to fly. The reason why *I* would never buy one is illustrated below.
I sat down last night and put my impressive credentials and education to work, and I came up with a device much simpler and cheaper than the sawstop, *and* which can be retrofitted to every saw out there. I bet it could sell for as little as $3 And it gets better, it prevents even the 1/16" nick in the finger. I've decided to call this new device a push stick. And to make it even better, I'm going to make it out of a piece of orange plastic. Actually, I really didn't have to think about it much, because there was this piece of orange plastic with "push stick" written on it sitting on my workbench, which cost me $3 at the last show. Where my impressive credentials and education come into play is, "I actually use the push stick." People don't accidently cut off fingers, rather, they negligently cut off fingers. If you don't understand the difference here, then you probably shouldn't be operating dangerous machinery.
Sawstop is trying to solve a problem which I originally stated was insolvable. They are trying to legislate against stupidity. And it can't be done. And sawstop realizes it because they have a nice little disclaimer which says that their product can only "reduce" injury, not prevent it. I would be much more impressed with the product if they'd offer to pay $10,000 for any finger sliced off while using a saw equipped with their device. I mean, at least "the club" will give me some $$ if my car is stolen while locked up. So my take on it is even they are not completely convinced their unit will operate perfectly as they are suggesting. In their demo, they show the blade stopping as a hot dog is slowly pushed into the blade. You know, I'm thinking that pretty much even the dimmest bulb out there is going to stop pushing their finger into a blade as soon as it gets nicked. What I want to see are some real world experiences. I doubt any of those pictures in their ad were from people who slowly pushed their hands into the blade. And I bet none of them were using a push stick either.
In addition, I also have problems with the safety issues and the net benefit to society vs cost. It is interesting to note that 70% of the injuries occur at home, where the average table saw costs between $100 and 500. So lets add the cost of $250 onto the top of these saws, putting them into the $350 to $750 range. Now you see why I predicted a boom in used saws and saw parts. That class of saws which is likely most dangerous will be the saws least likely to get the upgrade. $250 isn't much to tack onto a powermatic, but it is to a Ryobi benchtop model. So even if you make the feature mandatory on new saws, it does nothing about the old saws, and if anything, provides a financial incentive to keep those saws in service. I can't say that I blame the manufacturers for rejecting the technology. It will put those at the bottom end out of business and those with a broad range of saws (Delta) will probably take a pretty good hit. WMH group would come out OK. But the main problem is that the class of saws which is most dangerous will still be out there.
So basically, this comes down to me being somewhat resentful that someone wants me pay for something that I likely won't benefit from in this lifetime (because I use a pushstick). I guess maybe only those of us with a little common sense are sensitive to this. Frankly, I don't really need a GFI in the bathroom because I'm one of those people who is smart enough not to get into the shower with the blow dryer in the first place (yes, they do come with instructions to not do this). And I still prefer a chainsaw without safety features.
You get Jon's HIGH FIVE! Well said.
Jon
"$250 isn't much to tack onto a powermatic, but it is to a Ryobi benchtop model."
Amusingly enough, the $299 Ryobi seems to be the only saw available with a riving knife/splitter that follows the blade for less than a couple of grand. It's less exciting than SawStop, far cheaper once you get past the initial engineering cost, and not patentable at this point, but it's a nice demonstration that most vendors aren't interested in changing their designs for safety, patent or no.
"Auto manufacturers provided safety devices before they were legislated into place to ensure they were in all automobiles."
A true statement. What you are missing is that they were only available on high end models, and that they were eventually legislated into place because consumers "didn't see the value" - despite the fact that we now take them for granted, and even sued manufacturers for NOT having them in place before the legislation!
Airbags and seatbelts, as the primary case in point, were introduced long before they were mandated. Following your thought then, if there was a market, everyone should have been flocking to cars that had them. Unfortunately, this is not the case. What really happened was that consumers had the "it won't happen to me" attitude (sounds suspiciously like "I use a push stick so nothing will happen to me" - not that I am in ANY way wishing you harm!)
What happened? Society realized that the cost of people NOT having airbags or cars was considerably greater than the cost of an individual having to buy them. In other words, the cost to society (increased health care costs from injuries, etc) was greater than the cost of the airbags.
So we legislate. Because, whether we like it or not, accidents DO happen, and when they do, they are expensive - I don't know for sure, but I'd be willing to be the "all-in" cost of someone severing a hand/fingers is at least $100K and probably considerably higher, which would pay for a whole bundle of saw stops to be installed.
Now don't misinterpret what I'm saying - I'm not for unneeded legislation either, but like it or not, sometimes the masses (and government) DO know better....
d-
Edited 4/8/2003 6:15:11 PM ET by DM_Woodworking
DM,
The first airbags appeared on domestic cars in the early seventies. It wasn't until the mid nineties (15 years later) that they were refined enough, and cheap enough, to go into almost every vehicle.
Since we're there anyway, remember the government mandated auto safety/emission laws of the early seventies? There is a reason why virtually no one collects those 70's era cars. The technology to do what was mandated simply was not there at the time and those laws made for some pitiful cars. Yes eventually it [the technology] caught up, but it took a while (~mid eighties).
Back to the original topic of this thread. The SawStop needs refinement/redesign before it is going to become a common feature on the bulk of the table saws that will be in service for the next few decades. If they {The SawStop people) want to sell a slam-dunk product, then they should design one, not try to force a marginal design on the new saw mfr's.
Jon
Jon, your right. General Moters had installed driverside air bags in the early to mid 70"s. When Chrysler announced that the were going to introduce the bag as standard equeptment in the late 80's. Interestenly GM went out and evan found some of their cars in junk yards and the bags still deployed. I think what we have here is a good idea with a lack of adaquite funding. But as I stated earlier in this thread, The exposure of going to CPSC was an inexpensive move with international implications. I had some time today so I called several major workers comp carriers. I discussed the saw stop and its potential benifets to their insureds and they thought it could be added requirement to the policy. Large componies are often visited by insures to look for ways to prevent or minamize injuries. The liability carriers for the saw manufactures may see the benifets as well. Less injiries, less suits and pay outs and reduced premiums. I think of it as what it saves not what it costs. I don't like government involvement any more than the next guy. I thought I was one of the few who knew of the early air bags. Do you know of the dummy air bags? or the Canadian bag rebuilder who used gun powder as a charge? and then their are the counterfit. Sorry, I just got carried away. Ron
Actually, you make a good point here. Once they have a saw to sell, they should be selling it to the workman's comp insurers. Those that sell liability insurance to schools ect. If it works well, the insurers will probably start demanding it gets used. It's very likely people could see signifigantly lower premiums if they replace their tablesaw. If so, buying this saw will be a no brainer.
As far as those who think they should make a retrofit kit. As a mechanical designer, I can assure you that attempting to do so would quickly bankrupt them. Each model saw would require lots of design, engineering, and testing$$$$$$. If they start doing well, they may be able to pick one or two of the most commonly used cabinet saws, and offer a drop in kit. But, I'd do so only after I had a few hundred or thousand requests by people to do so. I'd probably just try to build a 1st class saw with a good fence and sell those.
Just looked at their website. You can preorder what looks like a decent contractors saw for $700. A nice cabinet saw with a riving knife costs $2300. Replacement blade brake cartidges were $59, or $69 for one for a dadoe blade. If they are good saws, seems like the few hundred extra dollars would be worth it, particularly if you had employees using the saw. I look forward to seeing an actual saw.
Edited 4/9/2003 11:08:49 AM ET by BILLYG83440
"As far as those who think they should make a retrofit kit. As a mechanical designer, I can assure you that attempting to do so would quickly bankrupt them. Each model saw would require lots of design, engineering, and testing$$$$$$. If they start doing well, they may be able to pick one or two of the most commonly used cabinet saws,"
Bill,
I see that you are a mechanical designer, That suggests that you have at least some education/experience as to the physics and constraints one might encounter in designing a blade brake.
You have asserted that making a universal [table saw] blade brake would bankrupt the company [that makes the SawStop].O.K. The capitalization of SawStop aside, that statement implies even more knowledge of the subject.
So, could you please educate us as to why it would be so cost prohibitive? Yes every saw is designed slightly differently, but they all also share a lot of common features; a 5/8" arbor, similar tilting and retraction mechanisms. In your professional opinion, why is there no way to cost effectively design a blade brake type safety device that could be retrofitted onto the vast majority of table saws that will be in the field for years to come, and would be designed around the various saw's commonalities? Just curious.
Jon
Edited 4/10/2003 11:47:22 AM ET by WorkshopJon
Edited 4/10/2003 11:48:15 AM ET by WorkshopJon
Jon, apologies for chiming in. Several reasons come to mind.
1. The force of brake activation would pit the bearings and/or crack the arbor & trunnion castings of a conventional saw. The saw would be ruined.
2. Space available and component geometry/tolerance varies widely from saw to saw. Engineering, manufacturing, and inventory logistics would be astonishingly complex.
3. Field installation, performed by the well-meaning but untrained saw operator, would greatly increase chances of the device not working correctly - a problem that wouldn't be evident until the device failed to protect the operator (too late).
4. Reason's 1, 2, & 3 above add up to a device that doesn't work as quickly or predictably as a purpose-built saw. Every tooth that passes through your flesh makes the cut that much worse. Sawstop's goal is to make the most effective blade brake possible. They won't get there by settling for lesser performance and accordingly increasing their liability.
Let's throw all of those limitations out for a moment. What if, instead of designing a saw with the most effective possible blade brake, we designed a blade brake to fit any existing saw and cost no more than $300 (the cost of many overarm blade guards). I'll head right to the bottom line with a guess...such a blade brake can be built but it would take 10x longer to stop the blade and wouldn't drop the blade below the table. That's 0.05 seconds instead of 0.005 seconds. If Sawstop leaves a 1/16" deep cut when struck by a fast-moving hand, this cheaper universal model would cut 5/8" deep. Maybe more since the blade stays up. The operator might still lose a finger. I don't think my 10x guess is high. If anything, it's probably low. The actual figure might be more like 50x - producing a dead stop in 1/4 second.
Regards, Dave
Thanks for chiming in, you did so while I was typing, and interestingly raised completely different, yet very important issues I missed. The most important one being that any system that stops a spinning blade in microseconds would likely destroy any saw not specifically designed to handle these huge shock loads.
Your time issues are probably pretty close.
Still, I think the biggest issue is electrical blade isolation, which is essential for sensing skin contact. It could be done on an existing saw mechanism, but would be fairly complex. Example, you need to isolate the entire blade mechanism from the cast iron top, which you'll be touching. Also, you'll wish to isolate this from the motor. On most saws, these items are all electrically connected. Nearly impossible to isolate just the blade holder on an existing mechanism.
So, you need to remove the blade arbor and put non-conductive washers between the arbor and table. But, you also have to isolate the bolts. That means you have to bore out the arbor mounting holes so you can put in an isolating bushing. Many saws don't have enough excess material near these mounting holes to allow this. Others use oversized or sloted holes to allow for adjustments to align the blade with the miter slots. Even the best case requires removing the saw arbor and machining the mounting holes. Also, anything else that touches the saw body, such as the elevation crank has to be isolated.
Then, how do you isolate the motor, or do you have to? I'm not sure.
Oh, and don't forget, you also have to have a totally reliable electrical connection to the spinning blade. If the connection fails at any time, it would have to be detected by the system and shut down the saw, or you have no saftey system at all.
It's kind of like trying to put airbags into an existing car as a drop in replacement kit. Sometimes it just makes more sense to replace the car or saw with one with the new safety equipment already designed in.
Bill,
Electrically isolating the blade might take the steps you list. The motor wouldn't be a problem - at least not conduction through the belts. It might be easier, in a retrofit situation, to isolate just the top and add a sheet metal enclosure to the cabinet to keep the operator from brushing against the rest of the saw that would be electrically live.
It is also possible that the sensing technology might mature to the point that the saw blade would not have to be electrically isolated. Already the sensor does not trip reliably if the operator touches the blade when it is at rest. The blade needs to be moving to produce the correct signal profile. Maybe more sophisticated electronics will be able to sense when an operator touches the table, and then sense when his other hand touches the blade too.
Regards, Dave
Dave,
"Already the sensor does not trip reliably if the operator touches the blade when it is at rest."
First, how much danger does a non-spinning saw blade present? Also, (I'm kind of inferring on this one based upon my limited research on my take on the SawStop design) doesn't the blade retract because the mechanism is capturing the inertial energy of the spinning blade? Do you know if that is in fact how it works?
Jon
Jon,
My point was that the sensor is already pretty discriminating. It can tell the difference between wet wood and a person and whether the blade is moving or not. Maybe with more development the sensor can be even more discriminating and the blade won't have to be isolated, which would simplify design & manufacturing.
The blade drops below the table to reduce forces on the arbor and trunnion assembly. Pretend that the saw is a car raised off the ground on blocks. The engine is racing. The car is in drive. The wheels are spinning about 130 miles per hour (blade tip speed of a typical saw). OK. Now kick the car off the blocks. If the car is in front of a concrete wall then you're in for some body work. If the car can roll freely across an open parking lot then you'll just lose a little tire rubber.
Sawstop's release of the arbor/trunnion assembly is the same as allowing this car to race across a parking lot instead of slamming into a concrete wall. Returning the saw to service requires the arbor/trunnion to be snapped back up into position, replacement of the cartridge, and contemplation of your good fortune to have avoided serious injury.
Take Care,
Dave
The retro-fit kit would be prohibitive. Many of the major parts would likely have to be replaced with newly designed parts. Then you'd have the cost of the basic Saw-stop components. And finally, the biggie, field installation and/or shipping to a suitable facility. As one putting together a recently purchased saw, lets just say that very few people would be thrilled about having to take down their saw so only the basic cabinet could be sent in for retrofitting. The owner is likely in for at least 6 hours of labor in the dis-and re-assembly. Then you have the disassembly and installation labor at the service center. Anyone thinking $250 for an add-on kit is kidding themselves. Of course the manufacturers are against a retro-fit kit. Once people are presented with the toal cost, I doubt you'd see many buyers. It would be cheaper to sell the saw and buy a new saw fitted with the device, much like the analogy of trying to retrofit airbags into a pre-1991 car.
Also, at least on the web page, saw stop makes a claim that their technology will reduce injury, but who is to say in a particular case what would be the injury without sawstop vs one with sawstop. You could lose three fingers with a sawstop and they could claim without the device you would have lost 4 fingers, hence they have "reduced" the injury when the case might be that their device had no effect at all.
Ok, fair question. I was speaking only of this particular design. It is possible that there is a different blade brake design someone will come up with that will retrofit easier.
If, all the saw stop did was slam something into the blade to stop it, it would be possible to build something that could be retrofitted to other saws easily. But, the way I understand it, the saw stop requires, bigger bearings, an electrically isolated blade, a mechanism that stops the blade, but also a mechanism that drops the blade below the table surface. Most of the commonalities you list are on parts that would have to be replaced to install a sawstop system.
I have spent lots of time electrically isolating things on welding systems. Since you want the current to go through a rotating blade, but not to other places because it would give you false readings, it takes a fair amount of work to do so in a way that is reliable.
Because of the blade drop, isolation issues, and bearing size issues, it seems it would require completely new mechanical components under the table top. I could be wrong here, but I believe the way the saw arbor attatches to the saw table top is fairly standard, but the location & design of blade tilt and elevation mechanisms differs signifigantly.
It may make sense for saw stop to spend the money to build a replacement mechanism for a unisaw or other major brand, assuming they could build one that fits most unisaw models. But, I would guess that a design to fit a powermatic or Jet would signifigantly differ. Could be wrong here.
It just seems like you would need to design a replacement kit for each brand of saw, some brands would require more then one model. Since you are not only replacing many of the most expensive parts of the saw, but designing for a limited market, I'm not sure you can design a drop in kit that would be signifigantly cheaper.
Eventually, once saw stop proves itself, and a market is developed, it is very likely we will see drop in kits for various saws. Particularly if some of the major saw manufacturers start building saws with this system already installed. It would be much easier for Powermatic to design a kit that works in their saws, then for an outside design team to do so. Having the detail drawings and original designers do the work for a specific saw saves lots of design time.
If Powermatic decides to design a saw to sell with saw stop already installed, they can design it so it not only works in their new saw, but retrofits to many existing saws. Thus, for them there is very little additional design and testing cost. Also, they can reduce the out of pocket cost by buying back the old saw mechanisms. They can then resell these as used replacement parts, or put them in a new saw body and sell these as economy saws. Plus, they have a large data base of people who already own their saws. They can directly market to their existing customers, making their advertising costs go way down and effectiveness go way up.
One good thing for us amatuers, if saw stop catches on, we may see a market with lots of good used quality cabinet saws for sell. Particularly if insurance companies give rate reductions to shops that have a saw stop saw. Could be a real advantage to some of us, and it's just possible that a couple years later we'll be able to upgrade these saws so they too have this safety device.
"I was speaking only of this particular design. It is possible that there is a different blade brake design someone will come up with that will retrofit easier.
If, all the saw stop did was slam something into the blade to stop it, it would be possible to build something that could be retrofitted to other saws easily. But, the way I understand it, the saw stop requires,"...
Based on your response to my question I can tell that you put a reasonable amount of thought into your response. Thanks.
You bring up good points, and seem to have a pretty good understanding of the forces that need to be dealt with in order to stop a saw blade nearly instantaneously from 2000rpm.
Let me bounce this one off you. Instead of aiming for a paper cut type injury, which is what the SawStop seems to do. In lew of losing a finger, let's say we set the standard at a 1/8" to 1/4" cut through a finger. Still way better than losing a finger completely. Do you think that this would change significantly the barriers to developing a retrofitable blade brake. I realize that this is probably beyond your area of specialty, but at least you appear to know more about engineering than me, and this forum is about the free exchange of knowledge and information.
Jon
>>>Instead of aiming for a paper cut type injury, which is what the SawStop seems to do. In lew of losing a finger, let's say we set the standard at a 1/8" to 1/4" cut through a finger. Still way better than losing a finger completely. Do you think that this would change significantly the barriers to developing a retrofitable blade brake.
My best guess is it wouldn't lower the barriers much. Someone here talked about the time issues. Still, much of the reason the sawstop keeps it to such a small cut is that not only does the blade stop quickly, but it falls away from your hand. Since while it is stopping, the blade also moves away. It's possible, that just stopping the blade w/o dropping it would result in a 1/8-1/4" deep cut. I frankly don't know.
Just a guess, but when the blade drops it probably disconnects from the motor so that you don't still have 3HP or more pushing against the blade. At least that's how I'd design it for several reasons. You don't have to stop the motor from turning. You don't impose a huge shock load on the motor, which going from 3000 to 0 rpms in 5 milliseconds would. So I'm guessing when the blade drops the blade arbor is no longer connected to the motor drive which spins down normally in a couple seconds because the power has been cut. I could be wrong on that.
The biggest issue is still the fact that taking a blade spinning at 3000rpms w/ 2-3 HP of force behind it and stopping it that fast will destroy the bearings in the saw arbor. Unless they are massivly oversized. It's also likely to bend the blade shaft, shatter a pully, knock things out of alignment, crack or shatter a casting, or just randomly break one of a dozen things that is suddenly exposed to forces it was never designed to handle. Biggest danger is it damages something that isn't noticed. Suppose that 6 months later that part fails suddenly, and the blade twists into the blade insert showering you with shrapnel. You may wish you'd just had your finger cut off.
Kind of like an old car my brother bought once. The previous owner had put a 440 motor in it. At a stop light he decided to show people just how fast it'd go, so he did a jackrabbit start. Well, he attempted to. When he goosed it, it snapped both u-joints on the driveline and the driveline rolled out from under the car. He's fortunate that's all that broke. Nothing in that car had been designed for the torque a 440 motor can put out. Similarly, even a good quality saw, isn't built to handle the shock load of instantaneously stopping the blade.
Bill,
I think the motor stays connected to the arbor. Power to the motor is cut, but the motor itself is protected from damage because forces on its armature cannot, by definition, exceed forces transmitted through the belt/pulley system. Forces much beyond the normal motor torque will result in belt slippage instead of armature arrest.
The blade stops in about 0.005 seconds, but the motor probably "spins down" by the pulley slipping past the belts for a fraction of a second. All you'll get is a squeal and a little heat. Forces on the armature are probably not much greater than that experienced during motor startup - typically no more than 300% normal operating torque.
Dave
As a followup to my post No.2 on this thread:
Once all the worthwhile contributors to this thread complete redesign of this sawstop device, and render it unnecessary to "think" while using a circular tablesaw safely, consider that CPSC might now mandate it be applied to ALL circular saws (radial arm, miter, chop, skill, etc) and next will be jointers, shapers, drill presses...wow, just think about it. How do you fit it to a bandsaw .... how about a sawmill, circular and others? Next come belt sanders, routers...
The public school contact was stupid, sure they would love it ... we all would, but in the end, their answer will be to close the shop once a "possible" lawsuit surfaces from a jointer mishap. Where do you think they'll get the money for all these upgrades? Assuming they were practical in the first place. The Liberals will go crazy with this (already saw markroderick chime in here .... we'll learn that legislation is the only way to achieve safety, in woodworking or WAR).
Under another thread, I asked a tentative visitor to an upcoming woodworking show to visit Sawstop and ask a few questions, re: cost to restore operation post-event, sacrificial saw blades, annual maintenance cost, test method .... weiner triggered event +$$$, +$$$$ , then to post their answers here. Are you all in for a big surprise!
I am pretty satisfied with my old Walker Turner, Duro, and Delta equipment ... and the safe operation instructions imparted by my Mentors, so I won't be following this thread any further .... there's a lot of constructive things I need to focus on and get away from this computer.
Best wishes, and work safely,
John
I know you're not reading, but you make a great point.
I hope this device is never mandated. It will make woodworking too expensive for most people. All cheap table saws would disappear. That's too high a cost. Also, you're right that the cost to a school or employer who doesn't provide tools with the best safety equipment possible could be tremendous.
I just don't see how that can be prevented. Our legal system is such that if a jury hears that if the school had only spent a few hundred dollars for X tool, this young man would still have his hand, the plantiff will probably get millions. The defense that to replace all their shop equipment with new safer equipment would have cost $25,000 which they just didn't have probably won't help much. So, it's possible some schools shops may shut down due to liability issues, but that has already happened in many schools. Many schools have eliminated, construction, WW, welding, auto shop, and other classes which have higher injury rates to lower insurance premiums. I'm officially not allowed to work in the shop at work because my workmans comp rate is about 1/3 if I am strictly an office employee. Our legistic society has many costs. It desperately needs major sweeping reform.
Still, I support this kind of equipment. Despite the idiots that try to believe everything can be made perfectly safe, and will try to force their views through legal action, it's still a good idea. An automatic blade brake is a very good idea on table saws, miter saws, radial arm saws, large band saws, & jointers. Perhaps even on large shapers & planers. Doesn't make as much sense on drill presses or routers, it's useless on a lathe.
If this equipment is proven, in time I'll probably get a saw with this feature. A couple grand to get this safegaurd w/ a riving knife doesn't seem too bad, if it comes with a real high quality saw. Or $700 for a contractors saw w/o the riving knife if it's a good quality saw. If you're already buying a saw, then the cost is a few hundred more then you'd spend anyway. Yeah you're spending hundreds for a safety feature you'll probably never use, but it's pretty cheap insurance compared to what could happen. Go to: http://www.woodworking2.org/AccidentSurvey/search.htm & search tablesaws. 180 accidents, many very serious ones, many where signifigant injuries could have been prevented with a saw stop type system.
I'll probably get one: If it's easy to reset the system (looks like a $59 cartridge is all that's needed; costs me more then that to walk in my drs. office). If it's easy to switch the cartridge for using a dadoe blade. If it holds up and keeps working in real world conditions. If it does these things, one day I'll have such a saw. Not just for me, but because one day I'll teach my children to use a tablesaw and I'll want that extra protection for them.
Go to: http://www.woodworking2.org/AccidentSurvey/search.htm & search tablesaws. 180 accidents, many very serious ones,
Not to diminish the suffering of the (presumably) 180 individuals involved, but let's stare at that number for a moment. The report covers how many years? I will stipulate that it does not reflect complete reporting of saw-related accidents. Still, all of 180 injuries and no deaths. That's bad news for a disappearingly small fraction of the population, but it would seem to add emphasis to Mark Roderick's earlier statement that saw accidents are not an impressive societal problem. How do those numbers compare, for example, to the damage from automobile accidents for an average weekday afternoon? Or even to kickback, which the Saw Stop ignores?
My beef is with the individual investors' attempt to use the power of the state to force other people to turn money over to them. If their product is effective and priced right, I hope they get rich the normal way--by succeeding against the competition in a market economy.
>>My beef is with the individual investors' attempt to use the power of the state to force other people to turn money over to them. If their product is effective and priced right, I hope they get rich the normal way--by succeeding against the competition in a market economy.
I agree with your beef. Trying to force every saw manufacturer to use their product is wrong. I hope they fail. Purchase of their product should be an individual choice.
The site I posted is simply one I am familiar with. It's part of another woodworking forum. The stories there are simply stories posted by members of that particular site. It's possible some of them aren't even true. Perhaps the product safety commission has some actual stats, I haven't seen any.
A seperate comment. Even if a safety feature only helps a small portion of society it can be worthwhile.
This product does address what I see as the most signifigant danger of a tablesaw, getting your hand in the blade. And does so in a very clever unorthodox manner. My hat is off to the cleverness of the inventor of this product. I also admire his tenacity to build his own saws when no one else would. Still, I disagree with him trying to legislate its inclusion in everyone's product.
You're right that table saw safety isn't a pressing societal problem. Relatively few individuals use table saws at all. Even most of those of us who do, only use them ocassionally. I'd be surprised if even 1% of the population uses a table saw once a month. Still, for those of us that are at risk, a product that seriously reduces the likelyhood of serious hand injuries, would be very worthwhile.
Saw stop doesn't stop accidents, it only helps to minimize injury in those instances where someone's skin contacts the blade. But, their cabinet saw will come with a riving knife, which does help prevent kickback, so they aren't ignoring that issue either.
For those who want to pay for this extra layer of safety, I'm glad it will be available.
For those who want to pay for this extra layer of safety, I'm glad it will be available.
I agree with you. The Saw Stop saw's availability will represent the very essence of a competitive free market. As I have said previously, I will applaud them greatfully if they succeed in that market. I just don't want them to rig the market with government intervention.
Edited 4/11/2003 7:33:04 PM ET by Donald C. Brown
Well, it appears we agree. I also hate to see activists, or inventors attempt to force people to do things the way they think they should be done. Let the market work it out.
Sawstop isn't going to be required by the FG. Without at least 10 years track record of moderately priced such equipped saws on the market, from several manufacturers, with all applicable patents expired or circumvented, there's no way in h__l that Sawstop will be made a legal requirement. Everyone here agrees on that.
I'd like to move on to HOW blade brakes may eventually become required.
First...they will hit the market. Someway, somehow, by Sawstop or maybe by someone else.
Second...the technology will mature, mass production will reduce unit costs, and market forces will "lower the bar" to make blade brakes fairly inexpensive. ICs to sense contact and trigger the brake will drop to less that $1. The devices will take many forms on many types of power tools. Circular saws, band saws, and routers will receive the most attention and innovation. Side note: Sawstop already has a bandsaw blade stop working prototype; it simply cuts the blade instead of trying to stop it. These devices will only add $10 to the purchase price of a handheld circular saw or router. They will only add 5% to the price of tablesaws and bandsaws.
Third...people will buy blade brake tools. Statistics compiled by insurance companies will prove that blade brakes save many times more in reduced healthcare costs than they add to the tool prices. The FG will get around to mandating blade brakes when more than half the saws and routers sold already have them. It will happen quietly. Few will notice, and no one will care.
Fourth...will a blade brake be a blade brake be a blade brake? Nope. Cheap saws will have brakes that barely comply with what will be a slack Federal standard. They will stop the blade in about 1/10 second and self-destruct in the process. Expensive saws will not only stop the blade in 1/200 second - they will also do so with no damage to the blade and no cartridge replacement needed. There will be no cartridge changing to mount a dado blade. Get a bandaid, push a reset button, and you're back working. These premium saws will be found in high volume professional shops. Most serious woodworkers will use saws that are a little more work to put back into service after contact.
Just speculating...
“Sawstop isn't going to be required by the FG….Everyone here agrees on that.
I'd like to move on to HOW blade brakes may eventually become required….”
Dave,
I agree with you, Sawstop is unlikely to be required by law. As far as what is the best way to get some kind of a blade brake that can adequately protect one against the loss of fingers in a table saw accident incorporated into saws in the field, I still maintain that it is to design something that is relatively easy to retrofit into existing designs.
The Sawstop people took the path of starting with a clean sheet of paper so to speak, believing that the positive benefits of a table saw brake would be viewed by the mfr’s of table saws (and the public) as being so great that they would be willing to pay license fees and perform a major retool of their products at significant cost to offer such a device. Not to mention that all those saws in the field that would go into the dumpster and be replaced with new ones. That doesn’t appear to be happening.
Furthermore, instead of going back to the drawing board, and redesigning their product, they attempted to force it on us with unsuccessful results.
Some contributors to this forum have pointed out that current table saw designs are not designed to withstand the physical stress the Sawstop imposes. That is probably true. But this all goes back to the constraints they imposed on themselves when they came up with their particular design. I still contend that it is economically feasible to design and mfr. a retrofitable device.
Jon
As long as we're speculating, how about this: within the next 10 years someone invents a laser that cuts wood much better than carbide steel. And moreover, this laser does not damage human skin. The entire tablesaw market is revolutionized and the poor Sawstop guys, who were about to finally realize their dream of financial success, are again cast into obscurity along with the proverbial buggy whip manufacturer. That kind of jagged, unpredictable advance tends to be how markets and technology advance. Any ideas for the laser?
How about water jet technology? That's what does a lot of precise thin stone cutting these days. Maybe ultrasonics? Perhaps cast cutter technology could be upsized to woodworking with diamond tipped cutters (to solve the tip wear problems) and dust extraction through the blade body (to solve the gullet clogging problem). Hmmm.
Sounds as if you're on your way.
You make some good points here. But, as of yet, we are not talking about a proven technology. If, they start to produce saws, and after extensive trials, tests, and several years of day to day use in high volume applications w/o major problems; then perhaps it will be time to talk about legislation. Unproven safety technology should absolutely never be required by legislation. In 3 years, if their saws prove themselves in actual use, I may buy one. In 5 years maybe it'll be time to talk legislation.
Someone brought up the safe firearms example. Why do police not want this? Well it's unproven, what if your trigger ring or whatever fails at the wrong moment? If a manufacturer comes up with a viable system, it would sell. There are many people who'd like to be sure their kids or a burgler can't fire their gun. But, while people have attempted to legislate to require such systems I don't know of any such system that you can actually buy now. As a cop I wouldn't want a system that had ever, even once, failed to let someone fire their own gun.
Let's not forget, that airbags while good, were initially required by legislation to be powerful enough to stop an unseatbelted man. Due to forcing car makers to make airbags overly powerful they have killed people. A good idea can be rendered less good by legislation.
I think you and DM Woodworking have hit the nail right on the head. Sometimes legislation is required because of the "It won't happen to me" syndrome, where individuals impose costs on society. Absolutely. But I agree that this particular technology is probably not one of those cases. People having fingers cut off by tablesaws does not strike me as a major social problem and probably never will be. Even if it happened a lot, which I doubt it does, the social costs would be minor. A trip to the emergency room, cleaning the blood from the beautiful cherry, some embarrassment, then back to the office. No real economic impact. Hell, you've got Sgian turning out fantastic work with a couple digits missing.
So while it is theoretically possible, I doubt that in this particular case a government mandate makes sense. And what's more, I don't think anyone needs to get worked up about having this imposed on them. Probably 10 billion would-be entrepreneurs petition the government each year for some law or regulation to help their competitive position, and only those with either real strong cases or friends in real high places (e.g., Halliburton or Enron) get what they want.
I drive a pickup without an airbag, so like the kids with the big pointy thing in the steering wheel, I tend to drive pretty carefully, as attested by a single minor accident in 30 years. Since my Toy only has 200K miles on it, its still pretty new.
Airbags have been a boon to orthopedic surgeons. On the surface, they do save lives, but you should see the costs associated with reconstructing a pair of mangled legs attatched to a reasonably intact upper torso. In the past, the whole body would get mangled and the health care costs were pretty low. Therefore, I'd be skeptical about claims that airbags reduce health care costs. Not to say that lives aren't saved, but lets not automatically assume those saved lives come with reduced health care costs. Case in point, Shock-Trauma in Maryland had to fire some neurosurgeons a few years ago. Turns out the surgeons were a little too good, and they were saving lives, but those lives they were saving were in pretty much a 90% vegetative state and it was costing the state beaucoups bucks to keep those people alive.
The point I'm making is that NO safety device is a substitute for common sense, and human nature (of the masses) unfortunately tends to rely on safety devices instead of common sense (perhaps because you can sue someone who makes a safety device, but you can't sue yourself for being stupid.) And one can't assume that putting on another safety device will automatically make things safe.
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