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Old hard drives are my favourite source of super-powered fridge magnets. I have a bunch of them holding up countless childrens' drawings. But the magnets themselves are stuck to base plates of various shapes, some with pins and protrusions which are sometimes unhelpful.

I am wondering what the best process would be to remove the magnets from those plates? They're definitely not stuck on solely by their own magnetism, so my best guess is "some sort of glue". I don't want to take a saw or screwdriver to them, because they're probably way too firmly stuck and also too brittle -- I'd just break them (possibly spectacularly so). I have tried sawing off the odd parts of one base plate, but getting the metal particle sawdust away from (or off of) the magnet is quite a challenge. I have also tried to twist and pry those pins off, but they're stuck in their holes better than my measly DIY-ers toolbox can undo (I don't have access to a metalworking shop).

So ... Heat? Acid? Magic? Some other SE stack?

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  • $\begingroup$ I'm thinking heat, but you'd have to be careful just how hot you get it. These tables might help, but you'll need to take an educated guess as to what type of neodymium magnet these are. And of course, you'll have to wear gloves when trying to separate the magnets. $\endgroup$ – BillDOe Sep 15 '18 at 20:30
  • $\begingroup$ Well I was lucky, I used a large old screwdriver and sharp tap from a hammer - came off a treat, ppe is a must. $\endgroup$ – Solar Mike Sep 15 '18 at 20:51
  • $\begingroup$ Maybe some piano wire or similar would be able to get in there under the edges without chipping the magnet. $\endgroup$ – norlesh Sep 16 '18 at 16:41
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    $\begingroup$ @BillDOe, the Curie temperature of Neodymium magnets is low. As low as 100C for some types. You definitely would not want to use heat. $\endgroup$ – user17527 Sep 16 '18 at 17:09
  • $\begingroup$ @besmirched, are you saying the data in the tables in my link are inaccurate? The lowest Curie Temperature according to it is 310°C. The lowest Working Temperature is 80°C for the N-Type magnets. If you get a neodymium magnet to its Curie Temperature, it will not recover its magnetism when cooled back to room temp, whereas it will if heated only to its working temperature. Or at least that's my understanding. And I did say wearing gloves is a must. $\endgroup$ – BillDOe Sep 16 '18 at 23:46
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You don't want to use heat on a neodymium magnet, as it will remove the magnetism. You are correct that adhesive is used to bond the magnets to the base. I've been successful in the same manner suggested by Solar Mike, with a screwdriver and hammer, but have managed to fracture more than one in the process.

If you wish a more controlled removal process, an arbor press or hydraulic press with a jig to secure the backing plate while applying pressure to the edge of the magnet may give the best results.

I've not tried a solvent, but acetone or MEK or similarly dangerous chemicals applied to the edges may help with release.

I think the screwdriver and hammer option is best, if you can afford to damage one or two. Alternative, a very sharp metal chisel (not wood chisel) or screwdriver with a sharpened edge will add a leverage moment to the shearing force, improving your chances.

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There are several approaches I've used to try to separate magnets like this from the base.
These are listed in order of ease (from my experience) and sometimes I'll use more than one of these at the same time. Sintered neodymium will fracture quite easily because it is powder that is pressed together under extreme heat and physical pressure. I think of it a bit 0like sandstone or a dried clod of dirt that holds together but can readily be turned back to power.

  1. Thicker steel target.

  2. A bigger magnet

(NOTE: I enclose the thicker steel target or larger magnet in fabric or nylon (like an sock or thick woven nylon bag) so that I can then the magnet from after I remove it from the old target and to minimize abrasion.

  1. Wood block ... push from the side. May need a vice or vice grips to hold the base in place.

  2. Thin non-magnetic thin metal sheet ... slip between the magnet and the target. A kitchen knife can sometimes work, but you may bend it in the process.

  3. Wedge... gradually slide between the magnet and target from the side. Ideally I use a wedge that is not ferromagnetic. This could be 304 stainless steel, hard plastic, hard wood.

  4. Lower the coefficient of friction between the magnet and the target with a chemical lubricant. I've used spray vegetable oil, olive oil, sometimes liquid dishwashing soap. put this around the magnet and then push from the side.

  5. Steel tool: screwdriver, hammer, crowbar, paint-can opener, etc. Be slow and careful as these can easily fracture the magnet (see below) and also the magnetic attraction may sometimes make it harder.

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