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  • #31
    Originally posted by challenger View Post
    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.
    works with aluminum too. one of my favorite practical science demonstrations
    -paul

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    • #32
      That Currie point where the magnet no longer sticks is the exact temperature you want to anneal the weld on a bandsaw blade. Use a magnet as you anneal and when it stops attracting the mgnet you are perfect.

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      • #33
        Where do I get the neo magnets? Much of my present supply was purchased from WalMart. But the last time I looked there, they had stopped carrying them.

        You can buy them on-line. Just an internet search or a search of the Amazon site will yield many hits. I purchased a package of 20 that way for a price that was better than WalMart's was.

        A couple of tips about magnets and chips in the shop:

        Yes, they will readily attract a bunch of chips. It may sound strange, but you can quickly and easily remove small chips from a neo magnet with a small piece of masking or duct tape. They stick to the tape better than to the magnet.

        And my favorite way for keeping chips off the magnets is to coat the face of the magnet with epoxy. I recess the magnet in the hole it is mounted in by about 0.010" to 0.015". Then apply a layer of epoxy in that recess. This seals the magnet in. It also eliminates any crack between the magnet and the part it is mounted in. The chips can get easily be caught in this crack and be difficult to remove. Eliminating the crack makes them easier to wipe off or to remove with masking or duct tape as suggested above. This small gap does not weaken the force by a large amount. I made my magnetic vise jaws this way and they do stay put on the vise.

        Click image for larger version

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        The 0.010" to 0.015" recess created by this assembly method is filled with epoxy. In addition providing easier removal of chips, this method protects the magnet from the wear and tear that is certain to occur in a shop environment. I have had these magnetic vise jaws in use for several years and had no problems with them.
        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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        • #34
          Paul - check out Ebay, you will find what you need. As stated in earlier post, China cornered the market on these, so you buy from them. Takes over a month to get them, but the price is right. Very handy for jobs like yours.

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          • #35
            Paul, I got a few for some special needs a while back of Amazon as well. There's oodles of shapes and sizes on both Ebay and Amazon. I think that a lot of the same vendors looking to make a buck or two are on both sites.

            For more general use there's also a lot of ceramic magnet options on both sites too. And in the case of the ceramic options bare ceramic cores and options for cores with pole end plates. And a lot of those while bigger are still plenty powerful for their size.

            Fasturn, thanks for that. I intended to include "I think it's... " or "I believe it's...." but missed that part. And clearly I was parroting what I'd read somewhere.

            Paul, while that's a trick option for holding the magnet it doesn't use the backing material to turn the opposite pole around and focus it around the edge of the face pole and increase the attraction. the foam and conical base to the hole will do a lot to disconnect the field from the metal. That is fine of you're using a non magnetic alloy anyway but it sucks if your goal is to turn the other side's lines around and use them. For that you need a very flat bottom and you also need the surface face to be flush with the cap's surface.

            If that's not the intent of your sketch then fine. But it's far from optimum if the goal is the most magnetic hold from the smallest magnet.
            Last edited by BCRider; 01-30-2021, 01:05 AM.
            Chilliwack BC, Canada

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            • #36
              Originally posted by Fasturn View Post

              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.
              Very nice.

              Help me to figurer out these lil bit of magnets please.

              My assumption is they drilled and made the thread before "magnetized" it? '

              It is not a common core type or neo mag. Just a big chunck of steel. JR


              Ol maggie....

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              My old yahoo group. Bridgeport Mill Group

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

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              • #37
                Have not seen a drilled and tapped chunck of steel that is also a crasey magnet,

                What is the Metal?/ JR

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                My old yahoo group. Bridgeport Mill Group

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

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                • #38
                  For all-around use, I ordered a dozen of the 3/8 dia x 3/8 thick neo magnets a couple years ago, they're great for just about everything around the house and shop. Paid less than $25 if I recall. Still finding uses for them, they are surprisingly strong. I also have some old hard drive magnets that will raise a blister if you get pinched in between them, and they are smaller than a postage stamp.
                  25 miles north of Buffalo NY, USA

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                  • #39
                    Originally posted by JRouche View Post
                    Have not seen a drilled and tapped chunck of steel that is also a crasey magnet,

                    What is the Metal?/ JR
                    Nice magnets! My understanding is that many magnets are made with powdered metal technology. Sort of like how they make inserts. Older magnets used lots of powdered iron, cobalt, and nickel alloys. Formed into shape in a mold, baked, machined, and then magnetized.
                    25 miles north of Buffalo NY, USA

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                    • #40
                      Originally posted by Paul Alciatore View Post
                      [snip]
                      I made my magnetic vise jaws this way and they do stay put on the vise.
                      [snip]
                      Let your drawings be an example of what us others can aspire to!

                      Your capture of the magnets by beveling the hole in the bracket is a great idea! I gotta' remember that.

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                      • #41
                        Originally posted by I make chips View Post
                        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.
                        I just attach the magnet to the oil filter.
                        Have not cut one open to check but figure they probably pickup some shavings floating by.
                        jeff

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                        • #42
                          I remember having a "monster magnet" as a kid - was a big plastic horseshoe shaped magnet with the magnets mounted into the ends and would pick up quite a bit but nothing like today's neo's --- still was kinda magical as a youngster,

                          times have changed and if you have small kids and think it would be cute to let them play with the little neo's you might want to think twice, although something to totally keep them amused with they also can be easily swallowed and then you better hope it was just one cuz if two or more then lots of times they will intersect in the small intestine and then connect two tubes together and not let go and cause the tissue to die off, huge problems and complications, that's if the kid survives...

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                          • #43
                            I bought a cheap magnetic swarf collector which was less to buy than I could make one for. It is a non magnetic stainless closed end tube with a number of magnets inside it. They can be withdrawn and any magnetic swarf just falls off. There is a guard halfway along the tube to prevent the swarf following the magnets as they are withdrawn.
                            ebay 232560219553
                            Last edited by old mart; 01-30-2021, 01:34 PM.

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                            • #44
                              Paul, re your drawing. In looking at it again I realized that this would be alloy jaws. So no reason for the pockets to be flat bottomed because it would not change anything. A set of soft jaws made just as you show would be nigh on perfect. Sorry for leaping to the wrong initial thoughts.
                              Chilliwack BC, Canada

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                              • #45
                                Originally posted by old mart View Post
                                I bought a cheap magnetic swarf collector ...
                                ebay 232560219553
                                "No exact matches found"

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