An alternative to Saw Stop?

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Forum topic by runswithscissors posted 01-22-2013 07:37 AM 6911 views 0 times favorited 232 replies Add to Favorites Watch
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3128 posts in 3031 days

01-22-2013 07:37 AM

This started on another thread, and was beginning to look like a hijacking, so I thought it would be better to start a new thread and see where it goes.

RonInOhio brought up an interesting point in that other thread, about developing tehnology to rival the SS. I’m thinking a better way would be not to stop the blade instantaneously, but to drop the blade instantaneously. Seems it would be less stressful on the equipment (arbor, bearings, etc.), wouldn’t ruin the blade, and maybe could be made so the cartridge (whatever the mechanism) wouldn’t have to be replaced.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

232 replies so far

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3128 posts in 3031 days

#1 posted 01-22-2013 07:46 AM

An update: Thinking continues to evolve. My Unisaw arbor pivots from the front, or near side of the table. If the arbor pivoted from the rear, or far side, of the table, the belts from the motor would tend to pull it down (not depending just on gravity). The switch should cut the motor at the same instant, to save belts from damage when they go slack (not actually sure whether that would be a problem). I’m not having any insight as to how the riving knife would work into this.

Another way that would allow the riving knife (which is the way at least one of Grizzly’s models works) is to simply drop the arbor straight down, rather than pivoting it down. But I do think the blade would get out of there most quickly by pivoting from the rear, pulled down by gravity and the drive belts simultaneously. I bet this could be made to be very quick acting. Dare I say it? Maybe even faster than the Saw Stop?

I’m trying to picture it: your finger (or hotdog) accidentally touches the blade, and POOF, it disappears beneath the ZCI. No damage done. You turn off the saw, press a button to reset the mechanism, crank up the arbor, and you’re in business again. Seems like it could work with dadoes as well.

It would be nice to hear other approaches, objections, caveats, etc. I know that this is the kind of topic that can bring out the best (and the worst) in woodworkers.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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1163 posts in 3696 days

#2 posted 01-22-2013 01:56 PM

I like it runswithscissors, this is the American spirit we love, create something yourself instead of complaining about what someone else is doing. Go for it!

-- Sam Hamory - The project is never finished until its "Finished"!

View SamuraiSaw's profile


513 posts in 2970 days

#3 posted 01-22-2013 02:49 PM

I’ve only briefly looked at a Saw Stop, so help me understand the process. I know a sacrificial block slams into the blade, but what causes the arbor assembly to drop? Is that a mechanical process or is there another piece that has to be replaced?

I wonder what might be a problem with leaving the blade spinning….......................

I hope this remains a discussion and not a pissin’ match.

-- Artisan Woodworks of Texas....

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2202 posts in 4164 days

#4 posted 01-22-2013 02:56 PM

It drops because the energy from the spinning blade has to go somewhere even after stopping it. It’s own inertia carries it below the table.

-- jay,

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854 posts in 3116 days

#5 posted 01-22-2013 02:56 PM

My Grizzly bandsaw has a motor break that stops the blade within 3 seconds. If that was also added (to the arbor) it could help stop the blade. I know that 3 seconds is a long time in an accident, but a motor brake, arbor brake and dropping the arbor would provide 3 points of safety.

I thought I heard somewhere that the guy who invented the stop saw method had a umbrella patent that would cover any emergency stop / safety mechanism.

From Jay’s comment I assume there is a quick way to disengage the raise / lower blade mechanism.

-- Jesse, Saint Louis, Missouri

View ChuckV's profile


3355 posts in 4533 days

#6 posted 01-22-2013 03:03 PM

I thought I heard somewhere that the guy who invented the stop saw method had a umbrella patent that would cover any emergency stop / safety mechanism.

Yes indeed. I received a letter from an attorney representing Saw Stop telling me that I have to stop hitting the off switch on my saw with my hip!

-- "Melodies decaying in sweet dissonance." - I. Anderson

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513 posts in 2970 days

#7 posted 01-22-2013 03:13 PM

What releases the arbor allowing it to drop and how is that reset?

Please forgive my ignorance, but I’ve really not paid much attention to Saw Stop before now.

-- Artisan Woodworks of Texas....

View helluvawreck's profile


32122 posts in 3872 days

#8 posted 01-22-2013 03:15 PM

I am seriously thinking about getting a sawstop. At 62 I’ve been using table saws since high school but have never had an accident that injured me. However, I’m not getting any younger and I’m sure my concentration is not what it used to be. So…....

helluvawreck aka Charles

-- helluvawreck aka Charles,

View crank49's profile


4032 posts in 3976 days

#9 posted 01-22-2013 04:23 PM

The Saw Stop patent would not stop you from making some other brake or drop and release method, but the SS method is absolutely the best one possible. Anything else will be second best.

I say that, not because I own one (I do not) or have any association with SS what so ever, just an observation of an engineer with 42 years of experience coming up with “outside the box” solutions to problems.

There are 2 main things about SS that make this design the best.
1- The brake cartridge stop block jams into the blade and stops it instantly. So fast that the motor and belts and even the arbor continue to rotate for a few milliseconds. It’s much harder to stop the mass of the motor than the relatively light blade in comparison.
2- The stop block jams into the back side of the blade so, due to the direction of rotation, the blade snatches itself below the table. There are no other energy sources needed because the blade rotation is directly converted into vertical movement in one direction (down).

These elements are what is protected by the patent because they are the essence of the design and the idea that created Saw Stop in the first place. This is what patents are for.

The flesh sensing technology is not unique. The touch screen on smart phones is similar technology.

If I were going to develop an alternate solution I would still grab the blade. There is no other way to stop something moving at ~200 feet per second, which is the tip speed of the teeth on a 10” blade spinning at 4500 RPM. But you would have to grab the sides of the blade, like a disk brake rotor to avoid the Saw Stop patent. Further, this brake caliper type devise would have to have some energy source.

Then I think a drive with a clutch that could disengage from the motor and engage a gear or cable to pull the blade below the table at the same time might be possible without infringing the patent.

Finally, even if this system could be made to work and not get into a patent piss fight with Saw Stop, it would surely cost more to produce and would not work quite as well. Not a system likely to be a market success.

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1632 posts in 3041 days

#10 posted 01-22-2013 04:36 PM

The Whirlwind CEO has a couple prototypes of a system which seems to be an electronic brake that is activated if you touch the blade guard. So basically it doesn’t have to be as fast, because it’s more a preventative thing.

It doesn’t ruin a cartridge or a blade though.

-- Jim, Georgia, USA

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118161 posts in 4583 days

#11 posted 01-22-2013 04:53 PM

Saw stop does drop and stop when triggered. If just dropping the blade would work to protect your hands don’t you think they would have just done that?


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Jorge G.

1537 posts in 3481 days

#12 posted 01-22-2013 04:54 PM

Samurai and crank49 have it right, the kinetic energy of the blade has to go somewhere once the break engages. SS cleverly uses this energy to retract the blade.

Any alternative technology would have to preclude engaging the teeth of the blade to stop it, as I am sure Gass has completely covered this in his patent. Remember the guy is a patent lawyer and a PhD in physics, he is not stupid whatever else you think of him.

Having said that, we all know how the disc breaks in a car work. I am not an engineer so I don’t know how difficult this would be, but why not design something that acts like the breaks on a car, after all what we have is a spinning disc, just like in a car. Giving that the mass of a disc is so small I am sure break pads would be able to stop it pretty quick.

Carry on….this is my contribution. If you use my idea and invent one, you have to promise to sell it in Mexico… :-)

-- To surrender a dream leaves life as it is — and not as it could be.

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9158 posts in 3156 days

#13 posted 01-22-2013 07:51 PM

The problem with the brake pad design is that it doesn’t stop it nearly as fast. You would need to have it trigger BEFORE any skin touches the blade via proximity sensor. If you wait until your finger touches the blade, the blade would probably get halfway through your finger before it stops. Stopping it “pretty quick” won’t work. It needs to be almost instantaneous. The best way to do that is to jam something into the teeth (like sticking a stick through the spokes of a bicycle) like the SS does.

If you could develop a proximity sensor that would sense anything that’s roughly in the neighborhood of the blade insert and make it reusable, then it would work. Keep in mind though that if you get kickback and your hand gets thrown into the blade, it still may not activate in time.

-- The quality of one's woodworking is directly related to the amount of flannel worn.

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Jorge G.

1537 posts in 3481 days

#14 posted 01-22-2013 08:55 PM

You are assuming the break pad won’t work fast enough because you are comparing to a car, I think it would be a matter of testing. Remember, mass has a lot to do with this, I am sure the clamping pressure could be achieved to trigger the pads and break the disk in fractions of a second, just like SS.

-- To surrender a dream leaves life as it is — and not as it could be.

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2202 posts in 4164 days

#15 posted 01-22-2013 09:02 PM

Especially if the break pad engages on both sides.

-- jay,

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