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  • Unusual accident

    Never seen this before, I have used hundreds of discs over my career.
    https://s3-us-west-1.amazonaws.com/h...shoots_out.mp4
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  • #2

    Re: Unusual accident

    Happened to a friend of mine right in front of me! He figured he hadn't tightened the nut enough.

    Comment


    • #3

      Re: Unusual accident

      If the nut becomes loose and the grinder gets bogged down, the nut can spin off. Usually happens when the nut hits the backing washer before fully clamping on the disk.

      Most of the time i see grinder disks on too tight.

      Comment


      • #4

        Re: Unusual accident

        It’s happened to me once with newer grinders with brakes.... or not using the wrench to tighten the disk.

        A lot of welders I work with, just use their glove hand to friction tighten, they like to be able to grab the disk with their hand and undo. Their thought is the wrench is for undoing, The nut will get tightened on its own with every hit of the grinding wheel. This opens up potential unscrews.

        My second thought is, that the wheel clamping surface was less than 1/8 (and there was no wrench tightening) and the wheel went into a free spin. The outer flange can be put on two different ways. More than 1/8 and less than 1/8. If you do this wrong, in this situation (without wrench tightening) it can easily happen.

        Use the wrench, isn’t that what it’s for??? Some should read the manual.
        Last edited by Matt Matt; 09-04-2019, 01:06 AM.
        For every action there is an equal and opposite reaction.
        Sir Isaac Newton.

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        • #5

          Re: Unusual accident

          UGH!

          Noel
          Noel

          "Being so impressed with the beauty of nature, I never cease to be amazed at how the
          'touch of the human hand' can transform it into another kind of beauty that is so uniquely human.
          "

          John Snow, Outdoorsman and Retired Teacher

          Comment


          • #6

            Re: Unusual accident

            When the disc flies off there's the disc and two round pieces that fly off. One of the metal bits looks like the nut, but the hole in the other one is too big to be the backing washer on the grinder .... maybe a nit of disc mounting kludging going on?

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            Click image for larger version

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            • Thread Continues Below...

            • #7

              Re: Unusual accident

              quite possibly the disc was too thin but the nut is right thread so should want to tighten not loosen. At least there was not a lot of mass to the disc.

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              • #8

                Re: Unusual accident

                Originally posted by iamtooler View Post
                but the nut is right thread so should want to tighten not loosen.
                Yup, right up to the instant where the disc touches metal, slows for just a millisecond and the momentum on the nut spins it off that shaft that has just slowed ....

                Comment


                • #9

                  Re: Unusual accident

                  Bosch just introduced a new type of lock on mechanism for grinders. Haven't overly looked at it in detail, but it follows along the lines of what they did with in conjunction with Fein with a lock-on mechanism (Starlock) that not only makes change overs much easier and quicker, but in the case of grinding wheels especially, much safer for operational use. I do wonder if this would mitigate such from happening.
                  Kevin

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                  • #10

                    Re: Unusual accident

                    I slowed the video so much and watched it about a dozen times.

                    My conclusion, is he/she had the first Drive/flange on upside down. The first Drive/flange is keyed for anti-rotation. If put on in reverse, it could damage the key/drive and have A greater possibility of unscrewing.

                    just my two cents.
                    For every action there is an equal and opposite reaction.
                    Sir Isaac Newton.

                    Comment


                    • #11

                      Re: Unusual accident

                      Originally posted by Matt Matt View Post
                      I slowed the video so much and watched it about a dozen times.

                      My conclusion, is he/she had the first Drive/flange on upside down. The first Drive/flange is keyed for anti-rotation. If put on in reverse, it could damage the key/drive and have A greater possibility of unscrewing.

                      just my two cents.
                      There is a good chance that is what happened or the little shaft diameter spacer was missing.
                      Egon
                      from
                      The South Shore, Nova Scotia

                      Comment

                      • Thread Continues Below...

                      • #12

                        Re: Unusual accident

                        I was thinking that the way he was holding the piece being ground was unsafe as well. Not only was he grinding too close to his bare hand as far as I was concerned, but did anyone else see the loose rag which could have easily have been grabbed by the disc?!
                        All the best,

                        Marty

                        - Instagram: @apexwoodworks
                        - facebook: https://www.facebook.com/Apex-Woodwo...0243458908979/

                        Secretary of Kingston Wood Artisans Inc. https://kwoodartca.wordpress.com/

                        Master Mistake Fixer (because I've made them all... at least once)

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                        • #13

                          Re: Unusual accident

                          Originally posted by MartyFromKingston View Post
                          I was thinking that the way he was holding the piece being ground was unsafe as well. Not only was he grinding too close to his bare hand as far as I was concerned, but did anyone else see the loose rag which could have easily have been grabbed by the disc?!
                          Yeah I was thinking the same thing, workpiece should have been clamped in a vice, no reason for your hand with or without a glove or a loose rag to be any where near the grinder wheel.

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                          • #14

                            Re: Unusual accident

                            Reading this thread you get the impression there is no way this guy should have been allowed near power tools, even a very uncomplicated hand grinder. Fortunately we all have free will and if we want to hurt ourselves we are free to do so, just hopefully not the guy near by who wanted no part of it .

                            Comment


                            • #15

                              Re: Unusual accident

                              He figured he hadn't tightened the nut enough.

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