SawStop false brake activation

[Eric Anderson]

I was wondering if anyone has ever experienced this. I had just changed my blade over to a dado blade, turned on the saw, and boom, the brake triggered. Nothing touched the blade and the blade never even got up to speed, so fortunately, the Dado set is probably OK, can't see any damage and since the saw never even got to speed, the damage to the blade is probably just due to carbide cutting into aluminum (little dulling, maybe). Unlike others that have talked about brake triggers, this one made no loud noise like when its fully spinning, as the set just disappeared.

I'm sending in the cartridge for testing, but SawStop Tech told me that the problem was likely the dado set was too close to the brake (it was set based on the "feeler" gauge that comes with the saw). He said when using a dado to increase the distance from the blade when using a dado blade several mm above the gauge setting. I've used the dado hundreds of times, same set up so still don't understand what happened.

I have had the saw for over 5 years (and dearly love it) and this is the first brake activation I've had. I haven't seen anyone discuss this particular issue, so thought I'd throw this out.

Thanks for any input.

[Todd Mason-Darnell]

Eric,

Just to check the simple things, you were using the dado cartridge with the dado stack?

Did you have the chippers on dado stack? I am asking because since the Sawstop works on a capacitance measurement, if the stack was on the edge of being too close, when the chippers cycled past the sensors on the brake, it could trip the mechanism (the increase in metal from the chippers will change the capacitance and fire the brake).

[sean meltvedt]

Eric, I have experienced the same issue, it was caused by the riving knife holder contacting the brake cartridge. As a cure, I made a wooden base the same thickness and shape of the riving knife, and clamp it in when I’m using dado’s or my 1/4 kerf blade. This cure has been working for at least 3 years👍

[glenn bradley]

I don't know about now with Laguna but, originally you sent the cartridge in and they verified the cause. If the cartridge were too close to the blade the saw should never have passed the power up sequence so I'm no buying that and would contest it. I read nothing in the manual for my 3HP PCS about spacing differently for a dado stack.

[Nick Decker]

Laguna? Maybe Festool?

[Wade Lippman]

Eric, I have experienced the same issue, it was caused by the riving knife holder contacting the brake cartridge. As a cure, I made a wooden base the same thickness and shape of the riving knife, and clamp it in when I’m using dado’s or my 1/4 kerf blade. This cure has been working for at least 3 years

Can you explain this more fully? How can the holder contact the cartridge?

[Chuck Nickerson]

My one false trigger happened on a very hot day when I was dripping sweat. I strongly suspect my wet hand left sweat on the board which triggered the mechanism.
Since you're in Austin and it's summer that's a consideration.

[Simon MacGowen]

Eric, I have experienced the same issue, it was caused by the riving knife holder contacting the brake cartridge. As a cure, I made a wooden base the same thickness and shape of the riving knife, and clamp it in when I’m using dado’s or my 1/4 kerf blade. This cure has been working for at least 3 years��

This is the first time I saw or heard a suggestion like this. None of the PCS and ICS I have worked with dado cutters need any special jig or add-ons to make them work. The manual has not mentioned anything like that either. I hope the SS people (forgot his name here) should clarify about that. If it is a bonus safeguard, I would copy the suggestion.

I always check the gap after changing one blade to another, dado cutter not not, just in case.

Simon

[glenn bradley]

Laguna? Maybe Festool?

Doh! Brain-fade. :D:D:D Yes, Festool. Thanks!


This is the first time I saw or heard a suggestion like this. None of the PCS and ICS I have worked with dado cutters need any special jig or add-ons to make them work.

Ditto, something is wrong there. When a tool is not functioning as designed, call tech support. I do buy some budget tools like Grizzly that have known hacks to improve their performance. I also buy high end tools and do not accept anything less than what I am paying for. It is our duty to make manufacturer's responsible for their products :)

[Nick Decker]

I've had no issues using a dado blade/cartridge, according to the instructions. Can you imagine the liability issues if there were further instructions and SawStop wasn't making users aware of them?

[Eric Anderson]

I asked them about that, because I was dripping pretty badly that day (actually had to clean and CRC the table after I was done as those salt droplets rust fast), but Sawstop said that would not trigger the brake. But the problem was it triggered without any contact with the blade. The trigger happened on startup, hit the on paddle, and the brake activated, well before any speed was even built up.

[Eric Anderson]

Todd, I was using the Freud set, with the two outer blades and three chippers and with shims set to 3/4" undersized plywood. And yes it was the dado cartridge.

[sean meltvedt]

393329Simon & Wade; if memory serves, the free side of the riving clamp would be just be able to touch the outside corner of the brake cartridge where it slides onto the large pin. I dunno if it would contact with the 10” cartridge as I always have either the knife, or the guard in the clamp��
I suppose you could get an extra knife and cut it down if you don’t want to make one from wood.
I just added the pic this morning , you can see the rub line where the clamp contacts the brake during installation and removal.

[jerry cousins]

I had the same thing happen with my dado blade - no apparent reason. Sent it to ss for analysis - no real cause - maybe faulty circuit?? They sent me a replacement. Xcellent customer service.

[Eric Anderson]

Got a update from Sawstop today. They analyzed the cartridge and got some contradicting information. Blade sensor told them the blade was at 4000 rpm, but had only been on for 0.4 ms. The tech I talked to agreed that it was pretty highly unlikely the blade was at full speed 0.4 ms after being turned on so we discussed some possibilities for the fire, one of which was noted by Sean. He said it as a low possibility, but possible that the riving knife holder (NOT the handle) could have been the trigger. He also said that it wasn't a bad idea to put a small piece of cardboard in the riving knife holder and clamp it down to keep it from "rattling". Again Sean suggested this too (or similar technique). Other than that, the tech had no ideas, but SawStop is sending a new cartridge. The tech as very helpful and the service was great. I've had some dealing with Powermatic service and they solved the problem but were not nearly as responsive. SawStop's customer service is pretty excellent. So bottom line, a misfire, and no real explanation.

[glenn bradley]

Thanks for following up Eric.

[Simon MacGowen]

He said it as a low possibility, but possible that the riving knife holder (NOT the handle) could have been the trigger. He also said that it wasn't a bad idea to put a small piece of cardboard in the riving knife holder and clamp it down to keep it from "rattling".

I am totally not buying this conjecture. I happened to be at the shop with the ICS and took a look at the holder which is probably half an inch or more away from anything. The loose part of the holder is an about 1/4" metal and could move only 1/16" (?) or so when I shook it here and there after releasing the lever.

How could the vibration of the saw (minimal) cause a contact between a blade and the holder UNLESS the blade is set outside the SawStop recommended limit. In that case the activation would be caused by the contact between the blade and the brake, not with the holder.

Anyone who has an ICS or PCS can easily verify my reasoning by looking into their saws. Even if it is a very very low possibility, since such caution has not been spelt out, I would demand SawStop reimburse my blade/dado cutter -- that is if I could prove the conjecture.

Nonsense is all I can summarize about the SawStop guy's conjecture...not to mention that no one I know has ever activated a dado cutter due to "vibration" in the past 12+ years. If he did not know the answer, fine and say it but don't treat us like idiots without thinking ability. The possibility is ZERO if one has the holder in front of him.

Simon

EDIT: Now that I have access to the PCS, here are the measurements: dist between blade and riving knife: 3/8"; between blade and holder: 1/2". The loose part of the holder could move about 1/16". In other words, the blade would contact the riving knife long before it hits the holder (anywhere of the holder, including the handle!). A low possibility? Lower than I could win the next lottery...

[Peter Christensen]

I'm kind of in Simons corner except he is looking at the normal blade and cartridge distances. The dado blade being 8" would be inch further away from the riving knife clamp or handle. While I'm glad they are sending you a new brake they should step up for the dado set too unless they can prove the misfire wasn't something you did. This coming from an ICS owner by the way.

[sean meltvedt]

Simon & Peter the blade is not making contact with anything. The theory is the riving knife clamp contacts the brake, not the blade. Hopefully this make more sense.
Sean

[Eric Anderson]

The sawstop tech also indicated that there is some RF signal involved with the break and that is why you need to properly gap the blade and break with the yellow "feeler gague". So somehow this RF signal may mean you actually don't have to touch. And as Sean said, it's the break not the blade that caused the trigger. Fortunately, since there was no real speed in the trigger, my Dado blade is not harmed (again 400 ms, less than 1/2 of a second), possibly dulled slightly, as there wasn't a lot of speed built up yet. none of the well documented "bangs" people tell about, infact no noise at all.

[Simon MacGowen]

Simon & Peter the blade is not making contact with anything. The theory is the riving knife clamp contacts the brake, not the blade. Hopefully this make more sense.
Sean

Thanks for your addition information.

The theory of the clamp touching the brake is as good as the "vibration" causing an activation. Again I did some measurements, this time about the clamp and the brake -

- dis between the brake and the underside of the clamp: 3/32" (1/32" x 3 as I could insert three credit cards between the clamp bottom and the brake)
- the clamp level is about 1/4" from the side of the brake (by sight)
- the loose part (jaw) of the clamp could not be moved down

The recommended spacing between the blade and brake is from 1/16" to 1/8". In other words, anything less or more will affect the brake operation. Too close it may cause an unwanted activation, too far the braking effectiveness may suffer.

3/32" is how far the bottom of the clamp is away from the brake. If a spacing of 1/16" is safe from causing an activation, how could the clamp with a spacing larger than 1/16" cause a misfire?

Any one of you is concerned that a misfire would happen due to the clamp/vibration, please double check your spring-loaded clamp installation. The reason the clamp could be too lose to the brake and cost you a brake replacement is that it has not been installed properly.

A lot of people use the SawStop (say with a cross cut sled) without the riving knife installed. The loose clamps do not seem to have caused misfires. As I already said, my dado cuts and others I have known have not resulted in any misfires.

Please correct me if or where I am wrong in my analysis. I would be happy to change how I use my SawStop to reduce any chance of a misfire.

Simon

[Simon MacGowen]

The sawstop tech also indicated that there is some RF signal involved with the break and that is why you need to properly gap the blade and break with the yellow "feeler gague". So somehow this RF signal may mean you actually don't have to touch. And as Sean said, it's the break not the blade that caused the trigger. Fortunately, since there was no real speed in the trigger, my Dado blade is not harmed (again 400 ms, less than 1/2 of a second), possibly dulled slightly, as there wasn't a lot of speed built up yet. none of the well documented "bangs" people tell about, infact no noise at all.

Please see my response regarding the spacing aspect.

Unless there is product defect in the cartridge, the RF signal would not activate the brake because no part of the clamp is closer to the brake than the blade/dado cutter is to the brake.

If I had to venture, could there be sawdust (in a humid shop) collected underneath the clamp that reduced the bottom spacing from 3/32" to under 1/16", causing an unwanted activation?

I would probably look further into the clamp set-up than believing that a properly installed clamp was the reason for the misfire. If the latter were the cause, I would categorize it as a design defect.

Simon

[Jon Nuckles]

I missed this thread when it was first posted. I had a trigger on start up with a regular blade cartridge when switching back from the dado blade to the regular blade. Same thing as the OP reported: immediate activation and no loud bang -- more like a click if I recall correctly. The tech said it was likely that the brake was set too close to the blade and I didn't question that theory. I had assumed that the saw would not start in that situation, but apparently it does. Sawstop did not offer to replace the brake and the blade was not damaged. I now make very sure to check the lights when changing blades rather than relying of the gap gauge. I haven't had any further false activations.

I did have a real activation around a month ago when kickback pulled my hand back into the blade. I got cut bad enough to require an emergency room visit and stitches, but I might have lost part of a thumb and finger without the brake. Sawstop does send a free replacement cartridge when you send in the one that sensed flesh, and I received that. I bought the saw mostly for it's superior dust collection and at my wife's urging rather than for the safety feature, which I was confident I did not need. I'm glad I had it.

[Simon MacGowen]

I now make very sure to check the lights when changing blades rather than relying of the gap gauge. I haven't had any further false activations.

I bought the saw mostly for it's superior dust collection and at my wife's urging rather than for the safety feature, which I was confident I did not need. I'm glad I had it.


Good reminder on the checking. I always wait till I see a solid green. (I also unplug it like working with a router and changing a bit before I do anything with the blade or riving knife! The switch alone is not enough for me.)

Every time I reset the gap, I make it sightly more than the min. (the plastic gauge), but still way under 1/8".

Your wife is good at keeping you safe!

Simon

[Roger Feeley]

What's this feeler gauge stuff? I didn't get a feeler gauge with my ICS 6 or 7 years ago. Is that a new thing? I think back then they said to use a nickel. The very first time I tried using a nickel, I dropped it down into the saw (might still be down there). So I found a piece of acrylic about nickel thickness and tied it to a string. There's a magnet on the other end. I keep it up on the dust collector arm with some other Sawstop tools in a little caddy. When I change blades, I plop the magnet onto the bed and I don't lose the gauge.

I guess you could say that I have an 'Idiot Gauge'.

[Roger Feeley]

Seriously, one indication of blade speed is the depth to which the blade teeth dig into the brake. A great guy at SS (Hi Roger) told me once that the worst thing is when somebody uses a tape to measure the blade to fence distance and touches the blade before it has come to a full stop. The brake fires and there just isn't enough kinetic energy to drive the teeth in much. Roger said that those are really hard to pry off. So, if the saw is just barely powering up, the blade shouldn't have dug in as far.

I've had two brake fires, both due to my mistake. On one, it was really hard to get the brake and blade off. Roger told me that I probably had adjusted the brake just a bit close. SS will still work ok but if you have a brake fire, the spring doesn't extend quite as much and there's more pressure. Those two events were in the first few months and I haven't had a brake fire since.

[Simon MacGowen]

What's this feeler gauge stuff?
http://sawstop.3dcartstores.com/Blade-Spacing-Adjustment-Gauge-_p_158.html

It sets the gap slightly more than 1/16" (the min.).

Simon