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  • #16
    The thicker magnet will be stronger, but there is a point of diminishing returns. Some of it has to do with airgap, some has to do with the thickness of the steel in the magnetic circuit. If the steel becomes saturated with flux, then a thicker magnet won't increase the holding power. If there's an air gap, the flux in the steel will be less, and an increase in the thickness of the magnet will increase the flux- but again only to the point where the steel saturates.

    If there is no air gap, and the magnetic circuit is closed (in other words there is no air gap in the flux path) then the maximum flux can build. If the steel does not saturate, then a thicker magnet can produce a higher flux in the magnetic circuit. To complicate matters, the magnet itself is akin to an air gap. Let's say you have a fairly long magnet in a closed magnetic path. The magnet material that is in direct contact with the steel will impart its flux directly. The material in the center of the magnet will only impart what it can from its distance from the steel. Say the magnet is 1 inch thick- the magnetism from the center of the magnet is 1/2 inch away from the steel. A magnet held 1/2 inch away from steel has less holding power than if it's 1/4 inch away.

    Complicating it further- the magnet material itself can only hold so much flux before it too becomes saturated. An N52 can hold more flux than an N35- the N52 can 'throw' more flux across an air gap. One thing I'm not sure about is how the length of the magnetic circuit affects things. For a given thickness of magnet, suppose you use a metal slug on one end of the magnet, which then requires longer steel pieces to complete the magnetic path. Does the holding power diminish?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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    • #17
      I've played with mostly N42 and N45 magnets. In general, I've come to the conclusion that soft steel equal in thickness to the magnets will contain the flux with little leakage. If the application has an air gap, then doubling the thickness of the magnet will create a stronger field in the gap. Tripling the thickness of the magnet will also increase the field, but not by as much as doubling the thickness. It starts to become more of a cost and size issue at this point.

      I've looked at many outer rotor model motors- so common on drones, and for airplanes. Many of these of of a pancake design, with a large diameter, but not long rotor. Virtually all of these use magnets which are no thicker than perhaps 3/16 inch, and many use much thinner magnets. There seems to be little to gain by using thicker ones.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

      Comment


      • #18
        Originally posted by Paul Alciatore View Post
        I have stacked the thin, "button" style ones to get greater attraction. But there are better ways if the layout of your design allows it. The best way to make maximum use of their strength is to use both poles. This is why the old magnets were shaped like a horseshoe: it brought the two poles (N & S) into close proximity so they could work together.

        The steel cup style pole pieces are designed to do this with the button or disc shaped magnets. They shape/force the lines of magnetic force from the rear pole around to the edges of the front pole. They can be very effective.

        But they are not the only way to reshape those lines of magnetic force. Where I have room for more than one button magnet I try to mount them in pairs on a steel back plate and use a steel plate as the element that is being attracted. The two magnets of one pair are mounted with opposite poles on that steel back plate. This is much like the geometry of those horseshoe magnets and the lines of magnetic force combine in the back plate effectively forming one larger magnet. Sometimes I use more than two magnets in a line on one back plate and then I alternate the direction of the poles. Four could be placed in a square arrangement, again with opposite poles to the adjacent magnets. This idea can work with any even number of button magnets arranged around a circle: N - S - N - S - N - S -, etc. until the circle is closed with a N - S pair.

        This idea can also work when the magnets are mounted without a back plate. For instance, I have a lamp fixture that I made with wood. The small "shelf" at the top needs to be removable so that the bulb can be changed in the actual, store-bought fixture. So I glued four neo magnets in the vertical piece and four steel screws in the shelf. The magnets have their poles in that N - S - N - S, in line sequence. There is no back plate, but they are closely spaced and the lines of force are curved from one magnet to the next and from one steel screw to the next. The magnetic "circuit" is mostly closed and that increases the force of the group of magnets.

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        This has been installed in my hall for years and the shelf has never fallen or even moved. Yet it can be removed very easily when the bulb needs to be replaced; hopefully a long time with an LED bulb.

        PS: in case you are wondering about the bird and birdhouse, my high school mascot was the blue jay, which is supposed to be a fierce, fighting bird. Other local schools often made fun of it at the football games, but we usually had the last laugh when the game was over. Many times state champions!

        When I saw that blue jay in a local hobby store, my theme for the project was set.

        I keep a supply of several sizes of these neo magnets at all times. I have used them in many places. Oh, my favorite "pick-up tool is another one.

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        The original magnet on the telescoping stick is holding the bracket for the light in place. It does have one of those cup pole pieces to increase the strength of that original magnet. But that field does not penetrate through the steel bracket it is holding. So I did add some additional neo magnets. And here I did stack the magnets.

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        At the time I did not know how effective that stacking strategy would be so I experimented. I tested it with one magnet and found a range of items it would lift and some others that were too heavy. Then I added a second magnet, stacked on the first. What I found was that a pair of pliers that I could not lift with the single magnet were firmly held by the stack of two. And some additional items that were even heavier could also be easily lifted with no danger of them dropping as I raised them up to hand level. There was a significant increase in the magnetic strength.

        I then went two steps further by testing with three and then four stacked magnets. There was a bit more lifting power with the third and perhaps just a little bit more with the fourth. But those increases were so small that I decided that the stack of two was the optimal configuration. I have been using this device, with those two stacked neo magnets, for over a decade now and it rarely fails to pick up the magnetic things that I drop. My aching back says a loud thanks! Both I and my back love neo magnets.




        That was a very interesting read and a clever way to fasten something that needs to be removed for access. I'm going to have to get some of those to keep on hand.
        Where is the best place to get them. I'm sure they are sold just about everywhere but as far as quality, if that makes any difference, and price.

        JL...................

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        • #19
          Kinda funny. Magnets (and magic) have always been a fascination for me.

          I still have my childhood toys that used magnates as the source of fun. The stack of floating magnets in a dowel. The forever spinning levitating top. Floating globe of earth, that one is currently on my dresser. The horizontal spinning "shape". Love magnets.

          I bought some of the n50 or 52 neos probably 15 years ago. They were just a pair. Could not go airliner, ground only. They came packed very securely, with some stern warnings.

          They are rectangles of 1"x1,5"x1.5". Yhey were separated with some packing and the warnings included making sure to put some "packing" between them so you can separate them if they are stored together. So I do that, folded paper towel works good.

          Thought they were going to be "fun". Not so much, too strong and fragile to do anything with them. So they have be packed away after about a week.

          Got some less powerful (n32?) pucks to incorporate into a wind generator. Small gen, just to see if I could. Pucks are 1" round by .5" thick. Its on the list of want to make things, after 15yrs.

          I actually love the magnets I harvest from the endless supply of dead hard drive around my house. They are strong, well coated and small. I hot glue them on a lot of suff.

          And speaker magnets. Love those for the shop. Place in a thick plastic bag and remove some shavings that are in a tight spot.

          Last but not least is a good ol magnetron magnet from a wore out magnetron (still havent found a use for those yet). JR



          They are small neo magnets that are cool. Very strong and small. Keep them in a plastic bag asperated by shape.

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          These are some of my shop magnets that just sit there waiting for a job My house garage is all metal at this point. There is a magnet within arms reach at anytime. Dont ask, cray cray,

          And yes, I am fully aware of magnets in and around "anything". I have an actual degaussing machine.

          I accidentally ruined our color tube TV as a kid. Took a magnet to the face of it. I was only 6 or so.

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          My old yahoo group. Bridgeport Mill Group

          https://groups.yahoo.com/neo/groups/...port_mill/info

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          • #20
            Lens's law is fascinating. Drop a magnet down a close fitting copper tube and, as mentioned above, it will sink slowly instead of drop like a rock.
            I discovered this while researching how to "mag" a fishing reel.

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            • #21
              Just a free and easy tip:
              Save the magnets from old computer drives and stick them on the oil pans of your car engine and transmission. Then coat them in epoxy so they don't rust. You can't imagine the amount of steel they attract inside the pan of a transmission. They work even better on aluminum pans as the lines of flux are stronger than when passing through a steel pan.

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              • #22
                All these magnetically riveting stories and no reply from QSIMODO on what he wants to do with his "general purpose strong magnets". QSIMODO?

                Like Paul I found that the very thin disc magnets got stronger if I stacked two but there was only a slight or no detectable gain with three or more. With that in mind if we're after more grip they do make disc magnets that are thicker to start with. Pre-stacked if you will.

                There's a bunch of YT videos on folks that have ordered up and play around with very large magnets too. So size does count in this case. It's crazy what a 10 or 20 lb rare earth magnet will lift. And the level of care needed to avoid it sticking to things where it may not be able to remove it or the item.
                Chilliwack BC, Canada

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                • #23
                  I as well have been fascinated by magnets all my life. One experience I had was interesting- sticking two pieces of metal together with a neo magnet and heating it. It wasn't more than a few seconds with the torch when the pieces fell apart. The magnet had lost everything. I experimented with re-magnetizing it- I tried to get it to take in the cross-wise direction, but it wouldn't. From face to face it would, and with either polarity.

                  I played with a neo magnet and a speaker magnet. I wanted to see if I could increase the strength of the speaker magnet, and it appeared that I could to some small extent, and only where the neo magnet touched. I could also cancel the magnetism in a spot on the speaker magnet, then bring it back by reversing the polarity.

                  It was interesting to me at the time when I learned that speakers are made with unmagnetized ferrite rings, which are then magnetized after the speaker was completely assembled.

                  Did you know you can make a compass by hanging a neo magnet from a thread? It's actually quite responsive.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                  Comment


                  • #24
                    Originally posted by BCRider View Post
                    All these magnetically riveting stories and no reply from QSIMODO on what he wants to do with his "general purpose strong magnets". QSIMODO?
                    Please, call me Len.
                    QSIMDO was a license plate I once had on a Ducati Monster.
                    I looked at the Monster with the humped back tank and it was done.
                    Also, Quite Simply It Means Ducati Owner.

                    As my inquiry stated, just for general use around the shop, house, etc.
                    Len

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                    • #25
                      https://www.kjmagnetics.com/ Everything you would ever want to know about magnets and then some.
                      Toolznthings

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                      • #26
                        So why is 303 stainless steel ( iron base metal ) non magnetic? Iron is very magnetic.

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                        • #27
                          Originally posted by QSIMDO View Post

                          Please, call me Len.
                          QSIMDO was a license plate I once had on a Ducati Monster.
                          I looked at the Monster with the humped back tank and it was done.
                          Also, Quite Simply It Means Ducati Owner.

                          As my inquiry stated, just for general use around the shop, house, etc.
                          Ah, that helps... And I'd say you've got a lot of ideas already.

                          I buy little packs of 3/8D x 1/8T Neo magnets and use them directly glued into holes drilled in wood to hang rulers and lighter small tools in handy spots. I've used them for spots on the machines in a couple of cases too. With care mind you. They LOVE attracting chips so I use them only where they are sheilded or easy to wipe the chips away.

                          For casual things like Fridge magnets and the like though we really don't need, and likely don't want the gripping power of the more powerful neo magnets. Or at least not the bigger ones. For a sheet or two a powerful grip gets annoying.

                          I don't use them much in the machine shop simply due to the way that they attract steel swarf. That gets very annoying very quickly too.

                          One use is on the ruler/indexing doohickey on my lathe. It takes advantage of the flat top on the tail stock to park a ruler and a magnet on the piece that clamps to the ram and another smaller magnet set into a small piece of aluminium angle stock as the adjustable pointer. Plus the ruler is in a handy spot to pick up and use for a quick measurement then put back so it sticks to the "traveler" shown gripping around the nose of the ram.

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                          The other spot I used a 3/8D x 1/8 neo magnet is on my shaper handle that I had to make up to fit the 1/2" square lead screws. I drilled the handle and then used a modified ground drill to flatten the end of the hole and stuck a magnet to the end of the shaft and put the handle in place. The magnet stuck more firmly in the handle so all you can see on the shaft is the two small flats for the wrench to aid with tightening the screw that holds the shaft.

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                          Other than that I've got some dollar store small magnets stuck to the steel splash guard on the wall behind the lathe to hold drawings. And they are well down towards the tail of the bed to avoid catching flying chips.

                          The wood shop has a lot more magnets to hold things simply because no one has yet developed a wood magnet... although fuzzy wool sweaters are not a bad try at this....

                          Chilliwack BC, Canada

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                          • #28
                            Originally posted by Fasturn View Post
                            So why is 303 stainless steel ( iron base metal ) non magnetic? Iron is very magnetic.
                            The alloying elements in the stainless stop the iron from orienting to produce complimentary poles or something like that. I find that it's still magnetic but very weakly.
                            Chilliwack BC, Canada

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                            • #29
                              Well, now you've got me thinking...do those tool holder strip magnets work at all?
                              I've got a ton of wrenches that just hide in tool chests now.
                              Len

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                              • #30
                                Originally posted by BCRider View Post

                                The alloying elements in the stainless stop the iron from orienting to produce complimentary poles or something like that. I find that it's still magnetic but very weakly.
                                Pretty close. During the 2 phase austinization it goes up the the Currie point ( 1400F ) at this point the permeability goes to about 3 or 4 which is only slightly magnetic in its annealed condition. Working it can make it more magnetic.

                                You can heat a magnet stuck on a piece of steel. When you hit the Currie point, it will drop to the ground with loss of magnatizium. See it done on YouTube. Also mentioned the magnet thru the tube. Those are Eddie currents acting like a brake from the outside -in. Rub a heavy magnet over a piece of aluminum ( non ferrous/ non magnetic ) it will push back like a second magnet. Those again are Eddie currents with the heavy flux. Those neodymium magnets are a game changer for so many applications !

                                Iron Nitride Magnets are stronger yet.
                                Last edited by Fasturn; 01-29-2021, 05:50 PM.

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