SawStop Accident

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  • SawStop Accident

    Much has been written about the SawStop and its safety, but there is one problem with it - if the blade is slowing down as in "turned off", and the blade is still turning, it does not function in its safety mode as it should.

    Here is a review on the pen forum (IAP): https://www.penturners.org/threads/s...le-saw.172253/
    If you are not a member of the IAP, you may not be able to see the photos. Not sure how true that is, but it was discussed once a few years ago, so again, not sure if you can view the photo.

    Yep, we all do dumb things, and that is exactly what a SawStop is supposed to prevent, but it seems there is a caveat to that. Be warned.
    Hank Lee

    Experience is what you get when you don't get what you wanted!

  • #2
    I imagine if the saw has been switched off and its spinning down but not stopped, then there is a situation.

    For one thing the saw blade has a lot of energy... at half speed it has 1/4 the energy of full speed, but it can still do some damage because its very sharp.
    Yet, as noted the retraction of the blade depends partly on the energy of the blade so it possibly will not pull down the same as when running full speed.
    The other thing it did not mention but I question is, if the power is switched off to the saw, does that remove power from
    the "flesh detection" circuit so that it does not even try to respond,
    even though the blade is still spinning at or near full speed and then slows down?
    Loring in Katy, TX USA
    If your only tool is a hammer, you tend to treat all problems as if they were nails.
    BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

    Comment


    • #3
      Originally posted by LCHIEN View Post
      I imagine if the saw has been switched off and its spinning down but not stopped, then there is a situation.

      For one thing the saw blade has a lot of energy... at half speed it has 1/4 the energy of full speed, but it can still do some damage because its very sharp.
      Yet, as noted the retraction of the blade depends partly on the energy of the blade so it possibly will not pull down the same as when running full speed.
      The other thing it did not mention but I question is, if the power is switched off to the saw, does that remove power from
      the "flesh detection" circuit so that it does not even try to respond,

      even though the blade is still spinning at or near full speed and then slows down?
      That was my thoughts also, but I think with the circuitry there, (my opinion only - from reading his experience) is that the circuitry is on even when the switch is off, but it only triggers if the blade is spinning. With all the thought that went into the design, it would not be difficult to program it to trigger IF: 1. the switch is off, + 2. motor is spinning*. BUT 3. does not trigger if motor is not spinning. This means that the safety circuitry is working.
      That seems to be what happened.

      Now the question is 2 fold:
      * 1. at what speed will the circuitry trigger the lock, even with the switch off?
      2. can a hand turned blade trigger the lock-down? I have (and I am sure others have) turned the blade by hand on my BT3000 to test runout.
      Last edited by leehljp; 11-10-2021, 09:30 AM.
      Hank Lee

      Experience is what you get when you don't get what you wanted!

      Comment


      • #4
        So the saw safety circuits are always energized or is there a separate switch to turn on the protection circuits?
        Loring in Katy, TX USA
        If your only tool is a hammer, you tend to treat all problems as if they were nails.
        BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

        Comment


        • #5
          Originally posted by leehljp View Post
          Now the question is 2 fold:
          * 1. at what speed will the circuitry trigger the lock, even with the switch off?
          2. can a hand turned blade trigger the lock-down? I have (and I am sure others have) turned the blade by hand on my BT3000 to test runout.
          My questions, too. I don't think I've ever not spun the blade when I changed the blade. So either that circuit is off when the switch is off, or it only triggers if the blade is spinning at a minimum RPM.

          Even with the power off, wouldn't a blade spinning down still generate some voltage as the shaft and magnets spin inside the coil? Could they measure that voltage and use it as a way to determine the speed?

          Comment


          • #6
            I occasionally turn my blade when checking the tilt angle with a wixley. I think this question needs some serious investigation.

            I noticed while assembling my SawStop contractor model that there was a warning label stating not to remove the saw shroud ( it has a plastic shroud around the blade that connects to a 4” dust collector hose under the saw ) that reaching inside the saw from the bottom could trip the brake and would result in serious injury. I though that this was typical lawyer speak because nobody in their right mind would ever crawl under a running table saw and reach upward into the heart of the beast. Reading this makes me wonder if they might be warning this could happen with the machine stopped, even from underneath the saw?

            I think I will fire off an email to SS and get an answer from someone that might know!

            Comment


            • #7
              Originally posted by LCHIEN View Post
              So the saw safety circuits are always energized or is there a separate switch to turn on the protection circuits?
              Loring, I am not totally clear on the specifics, but they do have a separate switch to manually cut the safety OFF - for when cutting fresh green wood with lots of sap, which has been know to trip the lock down and require new braking modules at $75+ each.

              That implies that the safety circuitry are separate from saw motor's on off switch, OR at least "active" apart from the motor switch.
              Last edited by leehljp; 11-11-2021, 10:21 AM.
              Hank Lee

              Experience is what you get when you don't get what you wanted!

              Comment


              • #8
                I talked to SawStop tech service today about when the brake is active. The brake IS active after the operator presses the stop switch paddle and the blade coasts to a stop. Shortly after it stops it’s diagnostics since the blade has stopped turning and a solid green safe light that is located on the paddle switch box comes on indicating the saw is in a safe condition. In this safe condition I was told the brake will not fire if the blade is touched or a metal object touches it. There is also a disconnect switch on the paddle switch box that kills power to the motor and brake that should be used when tinkering with the blade.

                So the pen turner forum person that touched the blade when it was spinning down, as well as another poster on that site that touched the blade with a measuring tape as it was spinning down all set off the brake…. As it was designed to do. As the service technician told me, using a reasonably amount of due diligence and not getting in too big of a hurry is the safe thing to do when using any saw.

                capncarl

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                • #9
                  Well, yes. Things like SawStop technology are not substitutes for thinking and due diligence.
                  You must still think and act as if that saw was the most dangerous thing in your life at the minute and there is no protection.
                  Loring in Katy, TX USA
                  If your only tool is a hammer, you tend to treat all problems as if they were nails.
                  BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

                  Comment


                  • #10
                    If there was a band saw that had a bade brake that would stop the band as quick as SS I would purchase one immediately.

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