Would you buy this safety device?

[Charles Krieger]

Assume I could engineer and build a safety device that would create a safety zone around the danger, ie saw blade or other cutter. If ones body parts entered into the safety zone an alarm would sound and the device would shut down. No braking would be provided so danger still is present from the spinning blade/cutter.http://www.sawmillcreek.org/images/icons/icon9.gif The safety zone could be set to the 3" rule or other specified distance. The alarm would possibly give the operator time to stop/pull back and in a commercial shop it would alert management to safety zone intrusions by employees.

This device could conceivably be added to most any stationary power cutting tool.

What if anything would such a device be worth?

[Brian Clevenger]

What if anything would such a device be worth?

Perhaps a finger or two. :cool:

[Frank Hagan]

I'd check with an attorney on this one. Because the "state of the art" for cutting tools is now a blade brake that prevents serious injuries, a proximity alarm that still allows injury may open you up to liability. Especially if the worker claims the alarm startled him, forcing him to jam his hand into the still spinning blade.

The problem is that you have to know how it would be dealt with in all 50 states for the US; we don't have uniform liability laws, but have 50 individual jurisdictions.

Your device might allow a different kind of blade brake to be used that doesn't require paying royalties to the current Sawstop patent holder and doesn't destroy the blade and braking mechanism, so it could still have some appeal to equipment manufacturers. They might be interested (and they have a handle on that liability problem already). It might also be of use in other trades to ensure only authorized people use machines (by means of an identifying RFID chip on a glove, for instance). Or for machines like punches and presses that can stop without having the momentum of a spinning blade (I can see it for those large sheet metal brakes and presses).

[Art Mulder]

What if anything would such a device be worth?

I don't think there is one answer to this. It's a sliding scale.

If the premium is the same as the sawstop, then I think you can expect a similar-sized market (though there are other good design features on those saws).

If the premium is more, then you can expect a smaller market.
If the premium is substantially less, then you can expect a bigger market.

I'd aim for the $100 price point. It's not a huge amount, and something that many folks would probably be willing to shell out.

...art

ps: but I wonder about that guy with the "startle" comment. Seems plausible. I think I might prefer if it just shut the machine off without an alarm. Or maybe just a blinking light to go with the shut down.

[Peter Quinn]

Would I buy it? No, I would not. It seems to give the appearance or feeling of safety with out providing any actual safety. Brakes, hold downs, power feeders, guards, splitters or riving knives, these things provide actual safety and stock control. I prefer not to be startled by loud noises in the shop when I am wearing head phones and focusing on not cutting off a finger, and for an alarm to be useful it would have to be loud.

[Anthony Whitesell]

The device is called (or nicknamed) a light curtain and they are current available and in use on all kinds of automated machinery. It would just be a matter of adapting one for this purpose.

[Chris Parks]

I don't see how a light curtain would work. As soon as you push a bit of wood up to the blade it would go off, or so it would seem to me. Now if you used an Infra Red Sensor that would work but I still wouldn't buy one for lots of reasons.

[Mark Elmer]

I'm in the not likely to buy group on this one too. My father taught me not to fear tools but to be sure that I respect them and what they can do both good and bad. I keep factory safety equipment in place if at all possible too.

I'd rather take the money that an "alarm" would cost and buy something that creates a barrier against contact with dangerous blade. An overhead blade guard is on my short list of safety upgrades for my tablesaw.

[Shawn Buonarosa]

I suspect that the vast majority of WW accidents happen so fast, that no matter what kind of audible alarm went off there would no chance to stop it.
So to answer the question, no I would not buy this.

[David DeCristoforo]

What we really need is a device that can see several seconds into the future and then provide some sort of warning . That I would pay for!

[Dan Friedrichs]

I've actually been thinking of building something like this, myself. A laser that would be deflected several times per second to "draw" a box sized 6" around the blade of a TS. Combine that with an IR camera, and you should be able to sense when a finger gets inside the box. At which point, you could kill power to the saw.

I don't think you'd need an alarm, though - shutting the saw down would be indication enough that you had violated the "safety zone".

I think this would be particularly useful on the jointer - I don't ever want my hands above the cutterhead, but since you can't see it, having a nice outline of where it's at would help.

I'd buy it - especially since the hardware required to build it would be minimal. I'm a electrical design engineer, and would estimate that something like this could be built for <$30. If I could buy this for <$100, I would. Easily.

I suppose it would mount on the ceiling above a tool, and the user would have to make adjustments to place the "box" where they wanted it on their particular tool.

[Don Bullock]

Charles, it all depends on what the final product actually does. Throughout history people have come up with inventions that the designer claimed solved a problem, but didn't. The old saying about building a better mouse trap comes to mind. What would sell i this case is a reasonably priced device that actually saved people from injury. In fact, as SawStop, has already proved, the cost doesn't have to be all that reasonable. BTW -- I feel that I must add that, due to the urging of my wife, I do own a SawStop.

[Gene Michael]

The best of woodworkers do stupid things from time to time and it only takes a fraction of a second of distraction to lose a finger. To me, the beauty of the Saw Stop is that it gets around those occasional moments when we fail to pay attention to what we're doing. Personally, I would prefer not to have a feature that might give a false sense of security. A healthy degree of fear of injury helps me pay attention to spinning blades. The legal issues mentioned above are also valid concerns.

[Rod Sheridan]

Assume I could engineer and build a safety device that would create a safety zone around the danger, ie saw blade or other cutter. If ones body parts entered into the safety zone an alarm would sound and the device would shut down. No braking would be provided so danger still is present from the spinning blade/cutter.http://www.sawmillcreek.org/images/icons/icon9.gif The safety zone could be set to the 3" rule or other specified distance. The alarm would possibly give the operator time to stop/pull back and in a commercial shop it would alert management to safety zone intrusions by employees.

This device could conceivably be added to most any stationary power cutting tool.

What if anything would such a device be worth?

Hi Charles, I doubt if there would be much commercial application for this as commercial equipment must have guards/physical barriers to prevent people from placing their body parts in harms way.

In Ontario where I live, industrial machinery has a pre-start inspection, conducted by an Engineer, or a qualified person under the supervision of the Engineer. The machine is tested/inspected to make sure that it meets all applicable codes prior to be placed into use.

Obviously the Engineer makes sure that there is no method of putting your hand for example in the machine while it's running. Once you have barrier guards, they provide a positive safety aspect, as opposed to a warning which does not prevent an accident.

Light curtains/pressure mats etc are often used to detect when a person is in a danger zone, however they are normally used on machines such as presses where they stop the machine from cycling.

Many pieces of industrial machinery also have worker positioning safety systems, such as "pull backs" on presses and shears where you wear gloves that are tethered to a retracting reel. If your hands are extended, the press won't cycle, and as a further measure they retract the cord when the press is moving to make sure your hands aren't in the die area.

The long coast time of North American wood working machinery would allow people to have serious injuries if you simply shut off the power to a table saw when their hand was approaching the blade.

Regards, Rod.

[Anthony Whitesell]

For any type of soft curtain (versus a hard blade guard) the problem would be mounting it and allowing for clearance for the workpiece to be fed through the blade. I have a few ideas for mounting options but I'm not putting to much thought into it. A good blade guard is the best and the second option would be a blade brake.

What is really too bad about the Sawstop is that it braking works using the actual blade and not a sacrficial blade/gear/ring/etc. also mounted on the arbor.

[Cliff Rohrabacher]

I think I'd prefer Arthur Dent's Safety Glasses.

They got progressively darker as something dangerous approached until they were completely opaque and dark.

This protected you from the ill effects of psychological trauma of the oncoming danger.

[Eric DeSilva]

What we really need is a device that can see several seconds into the future and then provide some sort of warning . That I would pay for!

Amen. Might help in Vegas too... ;)

[Don Bullock]

...
What is really too bad about the Sawstop is that it braking works using the actual blade and not a sacrficial blade/gear/ring/etc. also mounted on the arbor.

Anthony, you have a super idea there. Perhaps some company out there might jump on it and produce such a system.:D It could work on just about any woodworking machine.

[Jeff Duncan]

I'm another vote in the no thanks camp. I've been working in and around woodworking shops for quite awhile now and the one thing that seems pretty common amongst injuries, is the speed with which they happen. Generally by the time you realize somethings wrong, it's too late. Products like the Sawstop work b/c they are simply faster than human reaction time.
Also although I never recommend having hands too close to a cutter, there are some operations I perform that put my hands within what would likely be considered the "danger zone". Thereby causing false alarms which would really create a more dangerous situation than without such alarm.
I'm all for devices that make equipment safer but I don't see this one being in that category. What we really need is someone to take a Sawstop type mechanism and engineer it into other equipment, like jointers and shapers etc.. Something that could stop a cutter in a split second, before the operator even knows he's hit it, is IMHO the best type of safety device.
JeffD

[Anthony Whitesell]

After thinking about it a little more (and for the company that snooping here for ideas), I think the arbor nut would need to be redesigned. If the nut tightens in the direction of the load (tightens clockwise, spins CCW, load would be CW), If the shaft stopped suddenly, then the load from the spinning blade may try to loosen the nut. I'm just a mechanically inclined EE and maybe an actaul ME would have a solution.

[Matt Meiser]

Anthony, I've heard that problem mentioned as a possibility when someone uses a VFD on a table saw. Maybe a solution could be as simple as adding a small pin on the arbor that engages a hole in the blade. This seems like a modification that could be made to the blade even at home. They could just supply a small jig that has a drill bushing? If its was even an issue, they could have you drill two holes exactly opposite each other to prevent affecting balance.

On the original question, I would have to vote no for many of the reasons already stated. Just shutting down power wouldn't have prevented the accident I had with a router. And I think any effectiveness would be entirely dependent on the installation.

I've worked around equipment with light curtains. I'm not a safety expert, but thinking back it seems like they are usually placed far enough back that you couldn't get to anything dangerous before its danger is reduced or eliminated. And fast moving things--even things like robots that can be stopped in a lot less time than a spinning blade--are protected by gates. Some of the gates even have electromagnetic locks that engage when the equipment is in auto.

[Tony Bilello]

A zone alarm can be a distraction. What if you are making an unusual cut and start outside the zone ( no lalrm) then you enter the zone and have an alarm when you are partly into your cut? Lots of different scenarios there. Also, if you make difficult but samfe cuts with a jig it may be such that it would set off the zone alarm. So, you disable the alarm for these cuts, then the next cuts and after a while, you never use it.

[Cary Swoveland]

I question whether an alarm would be useful. One alternative is a device that almost instantly stops and/or withdraws the blade, ala Sawstop. Another approach, which I have not seen tried, is to almost instantly remove the operator. This could be done by having the operator wear a tethered harness attached to a spring, the latter held in an extended position with a thin wire that would be severed (e.g., with heat) when a proximity switch is triggered. Alternatively, the operator could wear an automotive-style airbag, again triggered by the proximity switch.

Cary

[Larry Browning]

What we really need is a device that can see several seconds into the future and then provide some sort of warning . That I would pay for!

But if it saw into the future that you were going to hurt yourself and gave a warning, you would then correct the situation, and then there would be no warning because you were never in danger. So the only time it actually would sound a warning is when you actually hurt yourself and you couldn't do anything about it. So your device that sees into the future might not be too effective either.:D

[Cliff Rohrabacher]

The safety zone could be set to the 3" rule or other specified distance.

My pinkies are often so close to the blade that there's no room for a gnat's wing in between. An alarm would startle the daylights out of me and ~ ~ ~ ~ ~ ~

[Mike McCann]

nope would not buy

[Glenn Howard]

How will this device distinguish a body part from the work piece? Without a method similar to the Saw Stop (which requires touch) I don't see how it could.

Without a brake, I doubt an alarm sounding if you get within 3 inches of the blade would do much more than startle you into moving ahead the other 3 inches.

The success of the Saw Stop is that the brake device is able to react more quickly than the human brain. This "danger zone" method still depends on the relatively slow reaction ability of the human brain.

Saw Stop got it right. Now if they're really smart, they're spending their R&D time while the patent is still in effect working on an aftermarket version that can be adapted to other brands of saws. And if they just got this idea from me, I'll expect a cut.

[Rod Sheridan]

My pinkies are often so close to the blade that there's no room for a gnat's wing in between. An alarm would startle the daylights out of me and ~ ~ ~ ~ ~ ~

Be careful Cliff, one under sized gnat's wing and you won't be able to type on SMC or FOG forums!

Regards, Rod.

[Charles Krieger]

Wow, this post generated a lot of good ideas and I want to thank all of you who contributed.

I was not thinking of a "light curtain" as I was aware of that technology and did not think that it would be practical for wood working equipment.

I originally posted here because I did not think I would buy such a device even if a practical model was built. I use the saw guard, riving knife, push blocks, sticks and hopefully caution.

The responses were really great. I especially like the idea of a break away pin, ring or some such to eliminate the cost of a new blade when the saw stop type of technology is used.

I do not work for any company, I am retired at age 70. I have no desire to start a company or do any engineering work for profit.

[Curt Harms]

I shake my head when I hear people lamenting about destroying a blade when a SawStop brake fires. If false firings were commonplace, perhaps that would be something to complain about. IT'S EASIER, CHEAPER AND LESS PAINFUL TO REPLACE 100 WW2 BLADES THAN 1 FINGER!!! That's presuming the finger(s) can be reattached.