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Sawstop Inventor Still Struggling to Save Fingers

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Re: Acquisition target?
Haldor   7/26/2011 4:00:54 PM
I don't believe this technology works for metal cutting applications since it is sensing the change in capacitance created by the blade touching a water filled object (you).  If you are cutting a metallic object then the blade is already grounded through the metal object and there will be no change to measure.

About the issue of mandating this on new saws.  There is a perverse effect of unintended consequences.  The most menacing wood working shop tool would have to be the shaper, yet they tend to have the lowest injury rates.  Why? Two-fold, for starters only the more experienced woodwork is willing to invest in a shaper so hopefully being more experienced he is also more careful.  But I believe the most important reason is that by their very design shapers scare the crap out of the user which makes them a lot more cautious and deliberate in their use.

The same effect happens in traffic.  A wider, safer looking residential street encourages speeding which in turn increases car/pedestrian accident rates.  That is why the current trend is to restrict (narrow) streets that have a lot of car/pedestrian accidents to make drivers less comfortable and slow down.  If adding sawstop technology makes a table saw seem less dangerous to the user then it will most likely result in increased injury rates rather than reduced injury rates.  While blade cuts from table saws are common they are mostly superficial.  The most common serious table saw injuries are caused by kick-back.

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npitech   7/26/2011 6:05:52 PM
A great invention and some manufacturers are using it. As a woodworker, I thought it was a great idea but:

When the invention first came out, Mr Gass tried to get a mandate that all manufacturers must use his technology which gave the appearance that he was not really interested in personal safety, he was just trying to force all manufacturers to pay him licensing fees.

 The early version could false detect and Sawstop destroyed your saw. Cutting green or wet wood could result in a destroyed saw. Most woodworkers loved the concept but not the implementation. If these issues have been fixed, I would choose a saw with Sawstop. The operative word is choose.  An invention should go to the market, not to the legal system, for acceptance.

William K.
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Sawstop: Must we all be forced to pay for it?
William K.   7/26/2011 9:45:17 PM
I am amazed by the comment from Timmmmy49. He evidently believes that all of us are so stupid that we must be protected by purchasing this sawstop system.

I agree that it is a remarkable invention, and quite an achievement. Now I would invite mr timmmmy to explain to us how we can continue to use the saw after this device triggers. Please explain the reset process, OK? The fact that is not explained is that after the device is triggered, a portion of the mechanism must be replaced, and possibly the blade must also be replaced. To make it even less convenient, the replacement parts will only be available from one source, and they will probably not be cheap. In addition, consider the location of the device inside the saw mechanism, which will not be an easy or convenient place to do any work at all.

I agree that persons such as mr timmmmy should never ever be allowed to do anything that may possibly be dangerous, since they may be injured. But, as an American, I believe that I am free, and that I should not live my life enslaved by the fears of others.

One more thing: every day more people may be killed in transportation accidents than are injured by power saws. Sometimes the results are woth the risk.

This comment is not intended to be inflamitory, but rather to point out that some of us do not wish to have our lives run by those who are in a constant state of fear.

Sawmill Engineer
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Sounds like a waiting game...
Sawmill Engineer   7/27/2011 1:35:35 PM
I think that the delays are just tactics the companies are using to wait out the patent on Sawstop.  That way they can design it however they like and maybe come up with something better.   Isn't there only 5 years or so left in the patent protection?

The design isn't really rocket science--just the fancy electronics to sense the flesh getting close to the blade.  One of the comments mentioned nuisance trips of the sawstip when cutting wet wood--presumably related to the sawstop not being able to differentiate between wet wood and flesh (or hot dogs!)  So the sensing method probably should be considered for improvement, too.

The rest of the system is the braking method. (the article mentioned a "spring brake") It is only really good for small, low inertia saws such as used in cutting wood up to 12" in diameter or so.  Don't shoot the messenger!  It's the physics of the situation.  Stopping a blade dead in a few milliseconds from a surface speed of several thousand feet per minute is no mean feat unless the inertia of the moving system is low. 

Consider using this on a larger diameter circular saw or on a bandsaw where the two bandsaw wheels look like big flywheels when trying to stop.  Your braking system starts to look pretty humoungous.   I shudder to think what might happen if instant stopping is mandated for big industrial saws--kind of like making a law that pi will be exactly 3!!!

Emergency stopping of larger industrial blades might be worth trying if there is no better guarding method that keeps operators out of harms way.  However, it will more likely be a "damage reduction stop" where the blade is stopped quickly, but not quickly enough to prevent a few teeth from cutting the hot dog.   In my game, (sawmilling) personnel are not even close to large blades so it's a non-issue, except for stopping them at break times to change blades.  Then DC injection braking is usually used for a non-emergency stop. The high inertia machines can take many minutes to stop, even with hundreds of amps of DC braking current. 

I can see power tool manufacturers offering their version of sawstop as a different model--for example Makita has been offering an electric hand saw with or without an electric brake for many years now. 



William K.
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Response to "sawmill engineer", about sawstop
William K.   7/27/2011 9:56:52 PM
The sawstop system is absolutely an incredible setup, snd it is able to stpo the larger blades "instantly". The setup that I saw a photo of has a quite strong aluminum alloy arm with some large steel pins well anchored into the arm. When the system is triggered these pins are forcfully jammed int the sawblades teeth. It is a violent metal to metal impact. It is not a frictin brake sort of stopping, it is not even as gentle as ramming a car into a bridge abutmaent.The stop is a lot more like a rod-through-the-spokes stop on a bicycle. So the blade would be stopped befor much damage could be done to a finger. The damage to the saw and the mechanism is not explained, nor is the detail of replacing the actuator trigger device described in any detail.

I would ask a question, though, which is, "how well does it work with the fine-toothed saws, such as some veneer blades?" My impression is that the steel pins engage the deep notch below the leading edge of the individual teeth. How would that function with a finer-toothed blade?

Sawmill Engineer
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Patents by the truckload!
Sawmill Engineer   7/28/2011 11:10:53 AM
William, you are correct....the sawstop, even though it mentions a "spring brake" in the blog copy, uses a bunch of different methods of stopping. 

I did a quick Google patent search and found interestingly, that Gass has quite a few patents in the field, but so does Black and Decker, which seem more recent than Gass.  One B&D patent I scanned had well over 100 figures, so it is pretty obvious that they are trying to tie up the subject very thoroughly.  Some of the Sawstop patents are dated 2000, so he has precious little time to capitalize on them before they expire.  I suspect that there will be lawsuits up the wazoo if this gets mandated!!

The stopping methods vary from gentle (a brake) to destructive (release of compressed gas to do something like the tossing a pipe into the spokes).  The was a bandsaw brake that looked like it might simply cut the blade when stopping, which is a slick way of getting around the intertia issues of the bandwheels.  I would be pretty peeved if I had "nuisance trips" with this kind of destructive saw brake!  I doubt that Mr sawstop has been in a sawmill when a 12" wide bandsaw blade, 40 feet long,  parts at 10K feet per minute. 






Az kid
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Safety Factors ie impairment
Az kid   7/28/2011 3:24:44 PM
   The website talks about an accident happening every few minutes where someone gets their fingers in the blade.  Question I have is what is going on in these injury cases.  How many of these like in the case of drunk driving were the result of impairment in the woodshop?  Drinking a few beers while running the saw is dangerous!!!.   Now if we get Sawstop can we drink and run the saw and be safe?   Put the beers up while running the saw.   Perhaps a breathalyzer test that prevents the saw from starting up under the influence would work just as well at preventing injury.  What do you think?     

   In the video of the hotdog, the blade is set awful high up.  We were taught to keep the blade no more than 1/4 inch above the top of the wood being sawed to reduce risk of injury.  

   Stopping the blade that quickly is bound to put a lot of stress onto it.   What is the risk of the blade shattering and metal shards flying out over the workplace? 

    It's a great product, but I think more thought could go into it and improve it in several details.  

User Rank
A nightmare that refuses to go away
applegrl   7/28/2011 3:42:28 PM
As an equipment designer and a frequent user of all kinds of saws, I cannot imagine how this idea just will not go away.  It sounds like a bright idea until you find out that it intentionally destroys the equipment.

Obviously, it would be applauded by a few who believed that they were "saved" by it, but how many false positives are there going to be that lead to the complete destruction of very expensive machines for non existent problems.

Sorry, but I for one am not buying it!  Like most everything we do in life, handling a saw is a calculated risk.  I accept that as is. 

I design control systems, drive cars, rig antennas and go SCUBA diving in the ocean, all of which have a degree of risk...and yes I frequently use a table saw and without the guard.

I teach people about the use of a table saw in simple terms.  You just think of the blade as a rattlesnake and as soon as you take you eye off of it, you will get bit!






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Re: Random thoughts on Sawstop
fire-iron.biz   7/28/2011 7:38:39 PM
A friend in the power tool industry obtained a video of the Sawstop in action when it first came out and it was clear to see the massive level of stress that was applied to the rotating parts - that was enough for me to question the viability of such a device considering the increased level of secondary risk.  I think it's a great concept but agree with everyone else that a friction brake assembly would be far safer and at least somewhat easier on the equipment.  As for the triggering mechanism, most of the places I've worked would be considered "extreme environments" (water, snow, ice, mud) which also means gloved hands and thus rendering any such trigger device pretty much worthless.  I'm not opposed to the concept, it just needs a lot more work.

BobGroh commented on guards being removed - you'll find that on some of my equipment too and for the reason that the guards often create more of a hazard than anything.  A few months ago I used a Delta brand table saw owned by one of my clients and I removed the guard after the first cut because it created a serious kickback issue.  I have an older Crapsman radial arm saw that I removed the anti kickback device because it would engage in a climb-cut condition increasing the effects of the climb and kickback making any kickback far more dangerous.  Guard on table shaper was removed because the guard spring forced the work into the cutter at the start of the cut - heavy work would get sucked into the cutter knocking the snot out of anything in its path (namely me).  I'm not opposed to guards, I'm just opposed to guards that are more of a safety hazard than the equipment itself.  Mark

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Re: Random thoughts on Sawstop
BobGroh   7/28/2011 10:41:39 PM
The use of the 'sudden stop' mechanism on the SawStop is the genius part of the system.  You absolutely must have something that reacts RIGHT NOW - in milliseconds - I don't think a friction brake or the like would do the job.  If you watch the SloMo shots on the mechanism you can see that the inventor does 2 things when a 'delicate part' is sensed - the SawStop jams the blade off AND jerks the whole blade assembly down and into the interior of the saw. It is impressive AND it works.

After a 'stop incident', you have to replace the entire saw stop and retraction mechanism (which I understand is a $100 or so expense).  Frankly I would be more than willing to pay for the new assembly in such a case!  After all, my finger/fingers/hand were just saved.

The saw stop and retraction mechanism is rather nicely designed to absorb the energy with a controlled collapse of the control arm and a few other niceties. Very well done.

And, yes, you still have to cope with other causes of accidents like kickbacks. But at least the chances of cutting off a piece of 'you' is greatly diminished.

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