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Review by RegP posted 448 days ago 2439 views 0 times favorited 7 comments Add to Favorites Watch
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As I reread my prior post on the sawstop a few things things come to mind.

The brake is triggered by contact with a living thing. If you are not gripping the hot dog, we taped one to a board, the saw will cut through it. It has nothing to do with grounding or the meat.

It is triggered by capacitance of your body, that contact and it is very slight, pulls the voltage down, because there is voltage on the blade through the arbor – not a simple thing to do – with very little current behind it. The voltage drop is what it senses to go off.

I believe false triggering wet wood nails etc. only happens when the operator in the, case of a nail, is in bodily contact with it when at the same time as it touches the blade. The saw then thinks is was touching the person. However it seemed that if a piece of very conductive material, such piece of the nail, was in contact with the aluminum brake it would also set it off.

We reported this to Sawstop and they concurred after testing and new brakes now have the tape on the surface in the form of a transparent sticker. If you own one ask to look at a new brake and see for yourself. A strip of packing tape may prevent a false trigger.

If I remember this right, and I might not, set a piece of wet wood on the table and slide it up to the side of the blade when testing. If I remember this right the light would go off if you took your hand away. Again it was the operator the saw was sensing through the conductive material.

Don’t test the using the tips of the teeth on a new blade, they are often coated with a varnish and prevent conductivity, when testing always use the side of the blade.

As for the standard contractors saw that is the one I bought and yes I would like it the be heavier, but I have it on the wheeled worksite cart as I move it to the job site. When in place I sandbag it to make it more stable. I wanted the light weight version, as you add longer tables and cast iron it becomes less portable.

1.75 is all the horsepower you can get from 110 volt. The sawstop delivers it well. I find it more than adequate for any task as long as it is not on a hundred foot extension cord. I bought my son-in-law an industrial version, he is a finish carpenter and he loves it in his shop and has yet to set it off in 2 years of use.

Hope I have clarified some thing for you. Sawstop is like insurance nobody wants to pay for it in advance and if you don’t have it when you need it you hope you can stand the loss.

RegP
It used to be that if you worked where you filled out an incident report or made up something like it when the brake was triggered, in other words it saved someone, sawstop would send a free replacement. After all they wanted the statistic. I don’t have personal experience, but I would try.

-- Mr. P




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RegP

3 posts in 452 days



7 comments so far

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Mip

304 posts in 681 days


#1 posted 448 days ago

I have been following this technology ever since it came out about 15 years ago. I remember reading something about the capacitance (I had to scroll up to get the right spelling) of the body to set off the brake since the body lowers the voltage. It is top of the line technology they have built in there, no doubt about it. I just wished they used the plastic brake instead of the aluminum one, the plastic doesn’t damage the blade. Could you answer me this: why did Sawstop go with the aluminum brake? I did post this question to Sawstop, but no response. That was a nice present you gave your son-in-law, by the way.

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bbasiaga

112 posts in 598 days


#2 posted 448 days ago

Without being on the inside at SawStop, I can only guess that with plastic the heat involved with dumping all the energy of the blade into the break could lead to melting, even just small areas, which could then lead to the potential failure to stop. Also, mass must play a role in the inertial breaking of the blade, and a plastic insert of the same size as an aluminum one would likely weigh less.

There are a number of high performance plastics that may solve some of these problems (if they are even the problem), but then the cost could very realisitically be higher than aluminum.

-Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

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gtbuzz

346 posts in 1044 days


#3 posted 448 days ago

RegP – do you by any chance have a picture of the difference in cartridges with and without the tape you talk about? Did they really implement this design change on your suggestions? If so that’s pretty neat and kudos for your contributions to the community.

Mip said: “Could you answer me this: why did Sawstop go with the aluminum brake? ”

The very reason that the plastic brake would be much less likely to damage the blade is pretty much the same reason it wouldn’t make a very good brake.

The aluminum in the cartridge is designed to absorb the energy in the blade in such a way that the blade can be stopped in time but also in such a way that it doesn’t destroy the saw. Essentially, you’ve got to have something that is stiff enough that it can absorb the energy, but not so stiff that it simply transfers all the energy. If you look at the design of the cartridge, it operates in a very similar manner to a crumple zone in a car. Much of the energy is absorbed via the deformation of the cartridge.

I think plastic would have virtually no chance at stopping the blade effectively. In all likelihood the blade would just tear straight through or best case scenario, it would be a lot less effective. For comparison purposes, your standard 2024 aluminum alloy is roughly 20-30 times stiffer than ABS plastic, and about 3 times stronger. There are some fancy plastics that can match aluminum in strength, however even those still only have a modulus of elasticity that’s an order of magnitude less than aluminum (and as Brian pointed out very expensive). You could technically design a plastic structure that’s as stiff as an aluminum one, but it essentially would have to be 10-20 times thicker. In this case, you’d lose all the inclusions that are used for the crumple zone and the cartridge would just fail before it stopped the blade. Not good.

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AlbertaJim

47 posts in 1032 days


#4 posted 447 days ago

Thanks for all the information. It helps explain why my saw didn’t trip when I hit a nail last year.

-- My Boss was a carpenter

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Marty5965

158 posts in 548 days


#5 posted 447 days ago

When all is said and done, $200 bucks or so for a new cartridge and blade is way less than the alternate cost….right? Thanks for the detailed explanation Reg.

-- Marty, Columbus, OH, learning every day....

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mbs

1422 posts in 1543 days


#6 posted 446 days ago

I discharged the brake by having the riving knife BARELY touch the blade when the saw was running. There is no reason to have the riving knife that close to the blade. lesson learned!

-- Sorry the reply is so long. I didn't have time to write a short reply.

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RegP

3 posts in 452 days


#7 posted 445 days ago

Thanks mbs I did not think of the knife touching the blade. Will check that out.

Re the plastic brake I suggestion by gtbuzz. I you were my student I would give you an A for the idea but having a university major in plastics myself some of the UHMW materials might come close but the cost and deterioration over time might be obstacles to overcome. Aluminum is not a bad choice in my opinion.

Yes we made the suggestion to Sawstop and I was pleasantly surprised at their reception to it. They immediately tested it and got back to us indicating that they say no problem with the tape as far as an undesirable effect and later when I accidentally tripped my own saw, I absentmindedly walked up to it to cut off a piece of 1 1/2 aluminum angle. I forgot to use bypass mode. It only hurt my wallet. I was surprised that the replacement had the sticker on the surface doing the job of the tape right from the factory.

The saw wont start if you are in contact with the blade. It wont start if you put in a dado pack without the dado brake. Brake is still active during coast down. Personal experience.

It works like a touch lamp electronically.

Some one asked how long it takes to change a brake. Not much longer than changing a blade it might add 2 minutes. Not a factor however a youtube of the procedure would be handy as you don’t do it everyday.

I guess I am surprised at the interest taken in my post. When the dust settles and suggestions/questions get posted I would like to rewrite incorporating more information into this and check all my findings again just to be sure. At the same time possibly address some of the misinformation that people have heard.

I have never spoken to S. Gass but I believe what he has done was right, difficult, and needed. If my information is correct this was offered to all the major manufacturers and they all were cut off at the pass by their legal departments based on the premise of what happens if it doesn’t work and someone loses a finger.
They would not even dare to risk manufacturing it. It took years and a great deal of money to bring it to market. The difficulties and personal sacrifice say to me it could not have been just for the money.

To put that in context imagine that we can’t add seat belts to our cars because of the legal question of what if someone dies or is hurt while wearing one? That goes on and on. Accidents do happen to the best of us. The technology is available and prevents injury. I wish I had been able to come up with it but I am not sure I have what he had to persevere and see it through. I only hope someone will improve on this technology.

-- Mr. P

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