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  • General use magnets

    Is it the "neodymium" magnets that are the strongest?
    Len

  • #2
    Yes. There are different strengths of neo magnets also. Look for a number like N42, N52, etc. The higher the number after the N, the stronger the pull.

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    • #3
      Originally posted by eKretz View Post
      Yes. There are different strengths of neo magnets also. Look for a number like N42, N52, etc. The higher the number after the N, the stronger the pull.
      What is the highest strength available??

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

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      • #4
        Get some from a trashed computer cd/DVD unit. They are very strong.

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        • #5
          Originally posted by JoeLee View Post

          What is the highest strength available??

          JL...............
          N52 as far as I know.

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          • #6
            There are also field concentrators available or we can make them. Like the cups sold by Lee Valley. By turning the field lines in the cup you'll get roughly 50% stronger holding power.

            The magnetic latches use a similar focusing trick with the two flat plates on the flat ceramic magnet. A trick which can also be applied to the flat plate or disc shaped neodymium magnets if you want to mechanically "turn" the attraction and use the edge instead of the face. Plus the plates gives you the two poles working together again.
            Last edited by BCRider; 01-28-2021, 01:03 PM.
            Chilliwack BC, Canada

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            • #7
              The neodymium magnets are available in a great variety of shapes, some with holes for fixing, they all have one thing in common, tha surface is nickel plated. That is because the magnet material is prone to be affected by corrosion. This must be allowed for when using these magnets, make the design fit the magnets, not the other way round.

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              • #8
                China has a stranglehold on the neo magnet market because they're the primary source of neodymium and their government has dumped magnets on the market for decades to kill all competitors. there is a company which has a patent on the sintering process or something pertaining to their manufacture, so manufacturers in the US have to pay a license fee to be able to sinter neo magnets, at least as of five years ago when I last did custom magnets for a custom high pole count BLDC motor. You are best off to find something full of magnets that is junk, and liberate them. Brushless motors like those used for traction applications (ebike) are a prime candidate because they're high pole count and need decent quality magnets.

                go on craigslist or ebay, find a bldc hubmotor off of some crappy thing like a hoverboard or ebike that's burned out. Pull the rotor off and punch the magnets out with a non-magnetic tool like a brass drift or a stick of delrin. They'll almost always be cheap nickel plated neodymium, have a high pole count so you can get 20+ magnets for super cheap. Most cheap motors will have flat bar magnets that get superglued or epoxied to the rotor back iron.
                -paul

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                • #9
                  Originally posted by eKretz View Post

                  N52 as far as I know.
                  Yes, that is what I have read. I have some N50 and kinda regret buying them. Too "attractive" to be useable for me. JR
                  My old yahoo group. Bridgeport Mill Group

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

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                  • #10
                    I've got a batch of N35 magnets, 30x30x15mm to rebuild a 4" long magnetic V block. The original 1.5" dia x 4" long Alnico magnet has lost much of its mojo, which is probably why it was marked as 'scrap' when I liberated it from a shut down workshop at work. The theoretical maximum remnant flux is very similar at about 1 Tesla, but the coercive force is about 25 times as high. In other words, they'll be as good as the best case of the original in perfect condition, but won't loose as much field strength in less than perfect conditions, Moreso because the existing magnet is Donald Ducked!
                    Last edited by Mark Rand; 01-28-2021, 03:19 PM.
                    Location- Rugby, Warwickshire. UK

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                    • #11
                      Not sure, but I think the highest strength Samarium Cobalt magnets are stronger than Neodymium- but probably not available. Either way, it seems that all types of 'super strong' magnets are subject to corrosion and must be coated with something. N52 does appear to be the strongest grade of Neo. Pay attention to the temperature rating though- Neodymium has the lowest temperature above which the magnetism will just disappear.

                      As far as a fridge magnet, the N35 I think is ideal- the N52 is overly strong for almost anything you'd be pinning to the fridge door.
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                      • #12
                        Originally posted by eKretz View Post

                        N52 as far as I know.
                        OK, if you stack them does that increase the strength ?

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

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                        • #13
                          Originally posted by JoeLee View Post
                          OK, if you stack them does that increase the strength ?

                          JL.................
                          Not that I have noticed. JR
                          My old yahoo group. Bridgeport Mill Group

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

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                          • #14
                            It does with the thin ones. Not the thick ones. The steel cup works even better though.

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                            • #15
                              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.

                              Click image for larger version

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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.

                              Click image for larger version

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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.



                              Originally posted by JoeLee View Post
                              OK, if you stack them does that increase the strength ?

                              JL.................
                              Attached Files
                              Paul A.
                              SE Texas

                              And if you look REAL close at an analog signal,
                              You will find that it has discrete steps.

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