(semi-OT) SawStop : Hard Information

[rcook5]

There's a lot of heat in the debate over SawStop, but not a lot of data. In an effort to do something about this, I went surfing.

Since there is remarkably little hard information available on SawStop

-- aside from what we get from the inventor -- the best source we have for both sides of the debate is probably the public comments on SawStop's petition to the Consumer Product Safety Commission to mandate the use of the device on table saws.

There's page after page of stuff that mostly translates into 'good idea' or 'bad idea', but there's also some hard information both from SawStop's inventors and the people who are unconvinced or in opposition.

First, a block diagram of how SawStop works is at:

CPSC filings are at:

petition, index and the first of the comments)

the most interesting section, containing the comments of Underwriters Laboratories and various companies and industry groups)

short continuation of section 2)

In reading this over several interesting things come to light.

1) UL refused to act on SawStop, saying it needed more development and testing.

2) In its petition to the CPSC, SawStop misrepresented UL's concern, claiming UL said it didn't have the ability to test the device.

3) According to SawStop there is already an industrial chop saw on the market which uses a quick-retract safety mechanism. (I haven't looked up the references yet.)

4) As a technical matter, granting SawStop's petition would have violated the CPSC's mandate by establishing a design rather than a performance standard.

5) Despite claims made here to the contrary that no one is working on saw safey, the saw manufacturers have had an on-going 'multi-million dollar' program to develop a safety device to prevent major injuries. One difference is the manufacurers have agreed to pool their patents to make any such device widely available.

6) According to SawStop the royalty they are asking is 8 percent of the wholesale price of each saw. (NB: Based on my experience this is a rather high royalty for a 'big-ticket' item like a table saw. 1 or 2 percent is more common, I believe. --RC)

7) According to the power tool manufacturers, saw makers who tested SawStop reported an unacceptably large number of false responses -- both false positives (tripping unnecessarily) and false negatives (not tripping when it should. They also found a lot of other design issues and pointed out the SawStop would have particular problems with direct-drive or geared saws.

8) According to SawStop most woodworkers would need more than one module since the modules are matched to the blade type. A dado blade needs a different module from a regular blade, for example.

Anyway, read through the filings and you'll have a much better idea about SawStop.

--RC

Projects expand to fill the clamps available -- plus 20 percent

[igor]

[snip for space]

How DARE you burden us with facts!!!

Great work, actually. That 8% royalty is huge, IMO and IME. It would be "merely" rich if it were for the wholesale price of an entire product that the licensor had invented. Or 8% of it imputed value within the TS. For it to be on the entire price of the TS, to which the sawstop inventor had contributed much less than the full value, places it in a land I've never heard of before. Perhaps if TSs were entirely fungible. And perhaps if the license was exclusive. But for a non-exlcusive license on an improvement (versus an entire product), it is quite interesting. FWIW, if that is truly the bottom line deal that the sawstop people offered behind closed doors, then it tells me that the guy has a peculiar sense of reality

-- at least in the realm of licensing, which leads me to color my view of anything else I might hear him say. Thanks for taking the initiative to dig this stuff up and to review it. -- Igor

[rcook5]

Yeah, I know. Violates the Internet Code or something. :-)

One of the wonderful things about the World Wide Web is the way it lets you go fishing for information on the spur of the moment. Potentially it has the ability to add a whole new dimension to our discourse.

Thank you for your kind words.

--RC

Projects expand to fill the clamps available -- plus 20 percent

[Charlie Self]

igor notes:

Yeah, it is, partly because it amounts to about half the mark-up the retailer gets for stocking and selling the saw (mark-up on tools in the major table saw price range run from maybe 11% to 17%).

Charlie Self "He has all the virtues I dislike and none of the vices I admire." Sir Winston Churchill

[Ba r r y]

The question is, from what number?

I've got several large dealers, including the actual bricks and mortar for two large web vendors, in the neighborhood. The webbie's stores actually resemble indoor flea markets more than a spiffy retail operation like Woodcraft. In fact, the floor demos at one of them are often put together finger-tight! Both stores were in business before the web as discount tool dealers, both also have Home Depot stores across the street.

Both web vendors sell brands like Delta, Powermatic, and Jet locally for 20% less than the other guys, often at lower prices than Amazon / Tool Crib. The last time I checked, neither web vendor had filed as a

503(c) with the IRS.

Barry

[Charlie Self]

Barry responds:

I don't know how they do it. Power tools in general have lower margins than hand tools and accessories, and the larger the tool, generally as above, the lower the margin. Of course, there are always exceptions, and some of these small dealers may band together to get a special deal better than that the larger dealers get (sure!). It's also possible that they stocked up when the manufacturer was offering the dealers a sale.

I don't see an HD across the street as necessarily a negative for a tool dealer. Increases interested traffic in the area.

Charlie Self "He has all the virtues I dislike and none of the vices I admire." Sir Winston Churchill

[Frank Ketchum]

Thanks for taking the time to post all of this.

"It is always on, unless the operator activates a bypass switch to allow cutting of metal or metal-claý materials."

This answers one of my questions. I wondered how it would allow an operator to change the blade of the saw without firing the second the operator touches the blade. My assumption was that when the power switch is off, the sawstop is disabled. I am not sure if this is the case because some injuries happen after power is turned off and the blade is free wheeling to a stop. So I guess maybe the sawstop is not disabled when the power is off and to change a blade you are supposed to activate the bypass switch? Does it make sense to offer / legislate a safety device with an automatic, built in, easy to use bypass? Maybe. Maybe not.

Frank

[GregP]

Thanks, that's good stuff. Not so good for SawStop :-)

[GregP]

That's getting close to the auto industry range. I wonder if there are volume discounts and/or rebates ? "High end" audio gear (which can run into the 6 figures) and expensive flyfishing gear is usually in the 25 to 35 percent range.

[J. Clarke]

One would hope that it doesn't fire if the saw is not spinning (considering that it has a computer onboard that's really not that hard to implement). The bypass switch is for cutting metals and other stuff that triggers the sawstop. Of course you may not know that something is going to trigger it until after you've replaced a cartridge.

[Ba r r y]

Neither do they!

One of them has a sign at the traffic light out front that says "Attention Depot Shoppers..."

Barry

[Ba r r y]

$8000 bicycles can run 35%.

Barry

[Frank Ketchum]

Right, except I don't recall seeing any sort of sensor which monitors whether the blade is in motion or not. It looks like the only sensors are the ones which detect a capacative change in the blade (ie, a finger or hotdog touching it). It would also need to know if the blade is spinning or not. This is why I believe the bypass switch is there. I of course am uncertain which is why I raise the question in the first place.

Frank

[Frank Ketchum]

While browsing through this document, one thing in the petition jumped out at me.

"2) .... so that a person will be cut no deeper than 1/8th of an inch when contacting or approaching the blade at any point above the table and from any direction at a rate of one foot per second"

I take this to be the spec that the device performs at, or close to it. One foot per second is a very slow hand movement. When industrial OEMs install light screens on dangerous equipment such as presses, they must do a safe distance calculation to determine how far away from the hazard point the light screen must be installed. The reaction time of the machine must be taken into consideration as well as the speed that a person's hand can move. The constant value that is used for such calculations is 2000 mm/second. This is equal to 6.56 feet/second. Think about it. Move your hand at about one foot per second. Slow isn't it? Is that the speed that you move around the workshop? No.

It appears that the spec of 1/8" cut at 1 ft/second is off by a factor of

6.5. To me is seems that in a real situation, a person could get cut 1/8x6.5 or a little more than 3/4". This obviously does not really do a whole lot to protect you.

The more I read about this thing, the more I am convinced it is a POS. That being said, it may eventually lead to something worthwhile.

Frank

[bridger]

do all saw injuries occur while feeding wood? I think not.

[igor]

Maybe there are some US companies that one would qualify. I do not know. But I do know that BMW, Saab, Mercedes Benz, Volvo would qualify. I think it is BMW that designed and is selling this incredible instant roll bar in its sports-style cars convertibles. When the sensors sense that a roll is happening, the roll bar deploys -- it hinges up, 90 degrees. I saw a video taken by an autobahn monitor camera of a guy flipping his car and being saved by this technology. Overall, I do not think that any US federal car safety requirement in the last 40 years that did not involve a technology already on the market -- so someone went first w/o prodding. FWIW. -- Igor

[Frank Ketchum]

I sure don't. That is obviously the speed in which the device is designed around. What percentage of amputations do you suppose are from people feeding the stock through the blade and continuing on right into their fingers? The more I think about this the more I think that the hand speed constant of 2000 mm/sec is inadequate. That is a hand moving under it's own power. Many injuries happen from kickback which can "throw" a persons hand into the blade.

Frank

[J. Clarke]

The purpose of the bypass switch is stated repeatedly in their literature. They never say anything about using it to change blades.

As to a sensor, I have never seen a photo or illustration that shows enough detail to be able to tell. They may be assuming that nobody would have his hands near the blade after he turns off the saw--not necessarily a valid assumption. But there are other circumstances under which you can get hurt with a Sawstop-equipped saw so they have clearly made _some_ assumptions about its use.

[Unisaw A100]

Bridger:

I came within a red cubic hair of severing the itty-bitty tendon (tenon in wreckspeak) running up my middle finger and not only was the saw unplugged the blade was off.

And that's about all I say of the matter except that saw maintenance can get a wee bit hairy at times.

UA100

[ted harris]

You must have landed at tyhe wrong address