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Belt Grinder shock problem solved

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  • Belt Grinder shock problem solved

    I'll admit that the technical expertise needed probably exceeds most of those on this forum and the cost is heart stopping, but I will offer my solution to static electricity shocks from a belt sander anyway. I took a length of 14 ga. stranded wire and soldered an alligator clip on one end, and one of those large paperclips on the other. I sprung the paperclip a bit and stick it on my ear, with the alligator clip on something grounded. Works great.

  • #2
    Or you could ground the frame of the belt grinder.
    Steve

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    • #3
      I'm not an electrical expert myself but I would have thought that electrically connecting yourself to the machine meant that if a fault did develop you would be more likely to get a shock rather than less.
      In addition to that if the machine is not properly grounded (which I read as an implication of Steve's post) by making that electrical connection, you are the path to earth.

      Michael

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      • #4
        The problem Horst solved involved draining the difference of electrical potential between the belt and sander and his body. While sanding, an excess of electrons are building up on the sander or on Horst. by connecting the grounding wire between himself and the machine, the electrons drain away as they are created, preventing a shock.

        Clipping the electrode to the ear conjured images of Frankenstein and electric chairs in my mind.
        Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
        ~Practitioner of the Electromechanical Arts~

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        • #5
          You got it Weston; everything is properly grounded - except me. That is the point. Ground - good : shock - bad

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          • #6
            Originally posted by Weston Bye
            The problem Horst solved involved draining the difference of electrical potential between the belt and sander and his body. While sanding, an excess of electrons are building up on the sander or on Horst. by connecting the grounding wire between himself and the machine, the electrons drain away as they are created, preventing a shock.

            Clipping the electrode to the ear conjured images of Frankenstein and electric chairs in my mind.
            You should ground the machine if it is not already grounded. I'm not sure that your ear is a good attachment point for a personal ground, I'd suggest that you pick up a wrist-strap ground at a local electronics shop such as Radio Shack.

            If you choose to continue with your present arrangement, I'd strongly suggest placing a 1 megohm or so resistor in series with the wire to limit any current flow to a safe value. Without it you're a lot closer to the electric chair situation noted above than you may think! FWIW.

            -bill

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            • #7
              Ok, that sounds a bit tongue in cheek but taking you at your word, it is customary (and probably required by law) to insert a resistor (around 1 megohm) in series with ground to protect against being electrocuted by 117VAC (etc) through the static protection.

              Readily available ESD wrist straps and mats will have the resistor built in. Like this one for $8:
              http://www.radioshack.com/product/in...ductId=2103808
              Or $26 with a cheap mat:
              http://www.radioshack.com/product/in...ductId=2102871
              The more expensive heat resistant (hot solder) and chemical resistant thick conductive rubber bench mats from companies like 3M were nicer, though more spendy.
              http://www.qsource.com/showproduct.a...er-25-x-6-blue

              Or you can simply discharge the static to the nearest cat's nose. :-)

              If you don't want a cord hanging from you around moving machinery (even one with a snap disconnect), there are floor mats with grounding straps for your shoes. Murphy's law says the cord will be pulled perpendicularly to the direction it unsnaps.

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              • #8
                The problem is not a lack of machine grounding. The belt itself is made of insulating material and builds up a charge on outer surface of the belt, exactly the same as a Van de Graaf generator. The same will happen with buffing wheels. Grounding oneself to the machine isn't always effective since all you do is to provide an even better path for the discharge. The only certain solution is to have a pickoff brush of conducting fibres mounted so it just touches the belt and drains the charge to ground. Even though the fibres will be rapidly worn so they don't quite touch it will still be effective. The charge that can build on a belt or buffer may be as high as 20 to 40 thousand volts. Of course, the current is negligible, in the sub microamp range.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  Mount a magnet in the path of the sparks and this will suck up the ferrous dust. The fur will quickly grow out to touch the belt and keep it discharged. For fun you could weigh some steel and the magnet before and after grinding and you'd be surprised at how effective this is at collecting ferrous dust.....
                  "...do you not think you have enough machines?"

                  Comment


                  • #10
                    Originally posted by Evan
                    The problem is not a lack of machine grounding. The belt itself is made of insulating material and builds up a charge on outer surface of the belt, exactly the same as a Van de Graaf generator. The same will happen with buffing wheels. Grounding oneself to the machine isn't always effective since all you do is to provide an even better path for the discharge. The only certain solution is to have a pickoff brush of conducting fibres mounted so it just touches the belt and drains the charge to ground. Even though the fibres will be rapidly worn so they don't quite touch it will still be effective. The charge that can build on a belt or buffer may be as high as 20 to 40 thousand volts. Of course, the current is negligible, in the sub microamp range.
                    That's what I was thinking. Use a grounded carbon fiber or wire comb to pick off the charge.

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                    • #11
                      Would it be better to clip the ground to ones "Groin" area??

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                      • #12
                        You can also spray the back of the belt with a shot of Static Guard spray. Lasts for a couple of weeks and smells pretty too. I steal, er-get a can from my wife.

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                        • #13
                          Hello,

                          You also get this static buildup in a sand/glass bead cabinet. With all rubber type gloves the static gets you in the arms. You can also see a good size spark discharge leaving the tip of the blast nozzle to the work . Gloves using fabric above the hand portion stops most of the problem.
                          Keeps you alert !!

                          Brian
                          Toolznthings

                          Comment


                          • #14
                            Originally posted by gearedloco
                            You should ground the machine if it is not already grounded. I'm not sure that your ear is a good attachment point for a personal ground, I'd suggest that you pick up a wrist-strap ground at a local electronics shop such as Radio Shack.

                            If you choose to continue with your present arrangement, I'd strongly suggest placing a 1 megohm or so resistor in series with the wire to limit any current flow to a safe value. Without it you're a lot closer to the electric chair situation noted above than you may think! FWIW.

                            -bill
                            if you READ my response it clearly says the machine is grounded. a loose paperclip sitting on my ear (keeping it away from the moving belt) is a far safer and cheaper solution than tying a nearly unbreakable wire to my wrist where it is quite close to the belt.

                            Comment


                            • #15
                              Originally posted by sasquatch
                              Would it be better to clip the ground to ones "Groin" area??
                              Try engaging brain before opening mouth

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