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Precision magnets!

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  • Precision magnets!

    Ahoi!

    I made a first set of laminated magnets that are ground all flat, parallel and square. We have something like this at work, but they are quite expensive to buy...about 300bucks for a 25x25x100mm magnet.



    They are very usefull for aligning workpieces to each other, act as a work stop, square up small parts in the vice and much more.

    Full writeup here:
    http://gtwr.de/projects/pro_toolmakermagnet/index.html

    Video Part 1:
    https://youtu.be/HBhnRvCnIcs

    Video Part 2:
    https://youtu.be/Marc0h7sGLQ

    And no, I dont worrie much about magnetising my whole tooling, its not that bad as long as you dont slide the magnets around on a part. But still, I need a demagnetizer one day
    Personal website

  • #2
    Interesting project Stefan. What was your conclusion on the Fog Buster? It wasn't clear if you were using it by the end of the video.

    Would you consider one for your mill or lathe?

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    • #3
      Very well made videos. Thank you, Stefan.
      Mike
      WI/IL border, USA

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      • #4
        I would like to build a demag unit, a video would be welcomed if you decide to build one

        I have access to one at work but it hardly works.

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        • #5
          Wow ! I really don't think I will ever be able to make a set of those magnetic blocks to his precision, but I learned a bunch of little tricks that will have to remember. Now if one of you guys find you have some spare time and want make me a set of the blocks for Christmas I would be a happy camper.
          _____________________________________________

          I would rather have tools that I never use, than not have a tool I need.
          Oregon Coast

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          • #6
            These blocks are awsome! I have some magnets left from my 4th axis/lathe headstock direct drive servo motor so I might give a try. Problem is they are quite big so I think that the block would be too strong, plus I don't have a surface grinder yet.

            The demagnetizer would be awsome. All my tools are becoming magnetized and I'm getting really tired. The one that gives me more headaches is my mitutoyo carliper, almost imposible to work with it now.

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            • #7
              Why didn't you put the pins in before the surface grinding operation? Epoxy wouldn't be needed then.

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              • #8
                Impressive. Neodymium magnets have become very cheap but make toxic dust when machined. Embedding them in brass with soft steel plates to guide the magnetic force lines makes a very nice and durable machinists tool. Thank you for the nice vids.
                I hear and I forget.
                I see and I remember.
                I do and I understand.
                Confucius (孔夫子)

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                • #9
                  A powerful demagnetizer is very simple to make. Find any old cheaply made 120/230 vac to something power transformer that has all the I laminations held on the core at one end. Remove that I section and that's it. Leave all the secondaries open and insulated. Don't run for more than 30 seconds or so to avoid overheating when powered. Turn on power and sweep the magnetized object slowly across the open end of the E core. Turn off when object is far away. Be careful not to place aluminum objects on the core. If you do that and engage power it can fire the object with a lot of velocity.
                  Free software for calculating bolt circles and similar: Click Here

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                  • #10
                    http://bbs.homeshopmachinist.net/thr...t=demagnetizer

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                    • #11
                      Originally posted by Evan View Post
                      Be careful not to place aluminum objects on the core. If you do that and engage power it can fire the object with a lot of velocity.
                      Hi Evan,

                      I'm not quite following your description of how you are modifying the transformer. What is going on to propel the aluminium objects?

                      I am planning to pick up a spool of enamelled copper wire to make a degausser. No need to unwind it, just leave it on the spool, crack open the inside of the case to find the other end of the wire, and run an AC current through it. Then simply pass the tool through the centre of the spool.

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                      • #12
                        There are many on eBay for a modest sum. I have one like the one in the link and it has worked perfectly for many years.

                        http://www.ebay.com/itm/DEMAGNETIZER...cAAOSwzaJYBLIv
                        Kansas City area

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                        • #13
                          Thank you all!

                          And also thanks for the ideas on the demagnetiser. I still hope to find an old industrial one for cheap.

                          What was your conclusion on the Fog Buster? It wasn't clear if you were using it by the end of the video.
                          I like it! I used it today on the lathe and its fine there too

                          Way more reliable than the Noga I had before.

                          Why didn't you put the pins in before the surface grinding operation? Epoxy wouldn't be needed then.
                          I thought about that for the next ones I make, but I suspect that it will be a pain to assemble

                          I might ditch the pins and do some other form of joinery...I am looking towards the woodworkers already. Something with tounge and grove maybe.
                          Personal website

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                          • #14
                            Stefan
                            A couple ideas for your assembly issues.
                            Drill your plates and c'sink opposing faces. The holes do not need great precision. When you butter the epoxy the c'sinks act like rivets. If you used slow set it is conceivable that a loose stack could be made and epoxy poured until the faces wet, then clamped. Should give better strength than just the shear face you showed.
                            You could chase rabbets (there's a woodworker's term) down two sides and lay in steel bars that just meet the steel outer plates, clamp tightly and weld the corner joints. Any electric arc process won't heat the work sufficient to weaken the magnets. The contracting welds should tighten the stack.

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                            • #15
                              Be careful not to place aluminum objects on the core. If you do that and engage power it can fire the object with a lot of velocity.
                              Eh? How come we never had any such excitement when bulk erasing stacks of 1" audio mag tapes all on aluminium spools?

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