A case study in involuntary magnetic body-modification

A few people have e-mailed me about this.

Big rare-earth magnets: They want to hurt you.

What you're looking at, here, is a sandwich. The sandwich's components are:

1: One large neodymium-iron-boron ("NIB") magnet.

2: The fingernail and finger-tip, mashed down to negligible thickness, of a gentleman called Dirk.

3: Another large NIB magnet.

Hackneyed though it is to say this, Dirk was lucky. He could have been luckier, I grant you, but he could also easily have lost a whole hand to rare-earth magnets this large.

You can read the whole grisly story here on the MagnetNerd.com site, the front page of which shows a couple of little half-inch-cube NIBs attracting each other through the thickness of a man's hand.

(The Magnet Nerd also has good pages about magnetic perpetual-motion machines and the various other evergreen magnet scams. And a line of chunky wooden implements to let you handle large NIBs, and pull the blighters apart, without losing any digits.)

The mutual attraction between magnets of all types increases, all other things being equal, exponentially as the magnets get bigger, and approximately with the inverse-cube of the distance between them. (That last part is the bit that really sneaks up on you.) So you can make an instant earring by sticking a couple of small NIB discs together with your ear-lobe in between, or you can smash your whole hand into wafer-thin steak tartare with a couple of magnets the size of cigarette packets.

I think it's brilliant that anybody can buy fist-sized NIB magnets from a variety of dealers - Forcefield ("WonderMagnet"), Engineered Concepts ("SuperMagnetMan"), and of course umpteen eBay dealers. I think the people selling them are generally very responsible, too; in product listings for the big buggers, there's usually a BE CAREFUL YOU IDIOT warning. And to my knowledge NIB magnets are generally very well packaged, too - collections of small magnets get a mild-steel wrapper, and really big magnets get great big double-boxed packaging, firmly holding the magnet in the middle of a large box.

The biggest magnets in this house are the two-inch-square trapezoid and two-by-one-inch cylinders from this old review. I don't know whether you could actually smash all of the bones in your hand by putting one of the cylinders on one side and one on the other. You'd probably just get a very nasty bruise. I'll leave the experiments involving gauntlets, eye protection and supermarket poultry to someone else, though. And the two-inchers ain't nothin' compared to what's on offer these days.

As I write this, a quick eBay search (if you use the not-often-useful "Price + Postage: highest first" sorting option) turns up a 4-by-1.5-inch disc for $US169.99 ex shipping, 2-by-2-inch cylinders for $US109.99, and, most terrifyingly, a two-inch sphere for $US139.99.

Spherical magnets have the problem that only a tiny area of their surface can be in contact with any other object - like another magnet - that isn't concave. For little sphere magnets - the quarter-inchers, for instance, that you can use to make impromptu rings or bracelets - this just means that they need extra-thick nickel plating so the little contact patches between the spheres won't quickly wear down to the brittle black ceramic of the magnet material itself.

A big NIB sphere, though, is aching to smash itself into other magnets just like every other big NIB, but is fated to deliver all of its terrifying impact energy to that one tiny contact point.

I imagine the X-rays of that victim would look quite interesting.

If you reckon it's time for everyone to start calling you "Lefty" or "Stumps", NIB-magnet dealers stand ready to assist you. The Engineered Concepts guy currently has a 6-by-1-inch ring magnet for $US425, 6-by-4-by-0.75-inch blocks for $US325, and wedges for the bold wind-generator maker (find info about this at Forcefield's other site, Otherpower.com) at $US720 for half of an eight-inch-outside-diameter ring.

Forcefield, meanwhile, will be pleased to sell you wedges suitable for making a 14-inch ring, for $US30 each. The rest of their range tops out around the two-inch size class.

(If you're for some reason not seized by an uncontrollable urge to maim yourself in an unusual way, I suggest Forcefield's $20 Grab Bag. It contains an assortment of different NIBs, none of which are big enough to give you anything worse than a blood-blister. If you're buying for a child - preferably one who's old enough to avoid swallowing more than one magnet - I suggest getting a large number of quarter-inch-or-smaller discs or cubes. They're cheap these days, and a lot of fun.)

28 Responses to “A case study in involuntary magnetic body-modification”

  1. Changes Says:

    Dan, please don't put such pictures in plain sight next time. Link them or something. There are some of us who get seriously freaked out about anything regarding nails, fingers and pain, ESPECIALLY if there's amputation (voluntary or not) involved. :(

  2. Daniel Rutter Says:

    The Internet is no place for girlymen.

    (Well, actually girlymen are welcome. It's just people who can't handle the occasional Penis Bird or severed finger who have a difficult time.)

  3. dazzawul Says:

    I'll Bite..

    Penis Bird?!

    And yeah, I can't help but cringe whenever I see a removed fingernail or something else of the like.. it just looks painful.

    But yeah, Changes, man up a little will yah, you're on the internet, at least it was just a finger getting smooshed by a stray magnet, and not something like http://www.meatspin.com

  4. Daniel Rutter Says:

    I have a feeling that this thread's going to be an interesting test of Blogsome's offensive-comment detector.

  5. kamikrae-z Says:

    Encyclopedia Dramatica is to memes as Wikipedia is to knowledge: http://encyclopediadramatica.com/Penisbird

    Having said that, if you want to play the trumps thing, BME Extreme is about as hardcore as I've seen. Google at your own risk.

    Oh, and thanks Dan - I've now got something to show people when they look at me incredulously after I explain how NIB magnets can actually be dangerous.

  6. RichVR Says:

    I stopped chewing on my bagel just long enough to figure out what the heck I was looking at. Meh. Now the Tree Man freaks me out. I've messed up enough to be missing a few bits from finger tips. They usually grow back okay. Usually.

  7. fawktastic Says:

    'I’ll Bite..

    Penis Bird?!'

    These words should preferably never follow each other in a sentence.

  8. Stark Says:

    Oh geeze.... I've seen injuries like that before - usually they are caused by carelessness in a machine shop though (high speed presses and extrusion machines can do some extraordinarily gruesome things to foolish people).

    I've got a stack of around 70 different hard disk magnets sitting here on my desk - the product of several years of destroying old hard drives - and they have bit me more than a few times. Nothing worse than a bruise or blood-blister though. I recently purchased one 2x4x1 inch NIB and I will make sure to never, ever, get it within a hundred feet of my stack of hard drive magnets. The carnage possible with that combination is not worth ever risking.

  9. fawktastic Says:

    I think a monkey eating your face would definitely be considered worse

  10. Ziggyinc Says:

    I'm enthralled by the Gauss Rifle. Do you suppose its even recoilless?

  11. Changes Says:

    I'm no girlyman, mind you. The penisbird does nothing for me. I actually got linked LemonParty from someone and it merely caused a raised eyebrow, and all Goatse does is make me laugh a bit. I can actually endure gurochan for a while before I start getting the feeling that I want to undergo voluntary lobotomy just so I won't remember those pictures again in the future.
    But amputations, finger torture/pain and the like hit my likely-unconscious-trauma button and I cringe and just want to tear my eyes out.
    Come to think of it, eyes too hit that button, but for some nonsensical reason fingers do it more.

  12. FuzzyPlushroom Says:

    How 'bout Funnelgirl?

    Nah, okay, I'll stop. Glad I'm not the only one amused by Goatse (do not click that) and LemonParty.

    On topic, someone showed me this yesterday, I believe. It was bad yesterday, it's bad now, and it's a good example of why Thou Shalt Not Screwe With Ye Olde Neodymium Magnettes.

  13. corinoco Says:

    Back in Uni days I was lucky enough to get to work on a student run building site. We had some gruesome industrial accidents, myself included.

    While unloading a pallet of laminated timber beams weighing about 2.5t, I managed to get my hand underneath it while guiding it onto another stack of timber. It was still rigged to the crane, and the operator managed to get it back up after only 2 or 3 seconds, but for that time I got to experience the feeling of almost all the bones in my hand being ground against one another in unusual ways. I was very lucky - we worked next door to the then still operating St.Henry's Hospital. The A&E team knew us all quite well by then, and I got away with severe bruising and a bit of cartilage damage that means I'm likely to get arthritis in that hand, and a keen appreciation of not putting your hands in a situation where they might get squished.

  14. dr_w00t Says:

    Man I hope I don't get fired because of this thread.

  15. kamikrae-z Says:

    OOOH oooh oooh! Miss! Miss! I just thought of another one! Worst guro pic I've ever seen is a person wrapped around a lathe. You couldn't really tell that it was a person though.

    [I know exactly the picture you mean. That little beauty took me back to the BBS days, when I and my friends gleefully collected all of the most horrifying industrial-accident, suicide-by-train and birth-defect pictures we could find for download. I still have a directory with a bunch of those pictures in it, and I added the lathe-accident one to it last year, for it truly is a sight to behold. (The next-youngest pic is dated 1996, but I think I actually collected it in about 1990.) -Dan]

    Hands down THE best motivator against wearing loose clothing around machinery. I also always wear eye protection because my first metalworks teacher told us the story of a student who got an iron filing in his eye, which stayed there until it rusted, became infected and eventually had to be removed surgically. I always have time to go and put on safety goggles.

  16. TwoHedWlf Says:

    I'm sure everyone who has ever had contact with hard drive magnets is familiar with the phrase, "Hey, these are really stro*SNAP*OOWWW!" I bought a dozen off Trademe and I think that took me exactly 5 seconds after opening the package.

    Got nothing on actual fingersmooshing.

  17. Itsacon Says:

    You guys must be talking about this site.

    Curse you, googling skills.

    The car accident is very flattering as well... (and one of the best arguments for seatbelts you can think of).

  18. Daniel Rutter Says:

    Oh, yes, that's the one. And a whole series of pictures of the event, not just one! How delightful!

    The one picture I'd seen before is distinctly reminiscent of this - non-horrifying, unless you have this comparison in mind - one of a mattress wrapped around a Jeep's drive-shaft.

  19. Red October Says:

    Two dimly related things... I have long hair. This, I discovered one day, needs to be pulled back when you use the big, 1/2" electric ram-drill. I lost a big chunk of hair, but nothing else.
    Also, for some reason, in my girlfriend's family, they have a history of such industrial accidents. Her grandfather lost a finger in a band-saw, she had her hand drawn into a printing press (No severe lasting damage), and her daughter had a similar incident with a band-saw, but kept the finger. I can offer no explanation for these coincidences, but I can say with authority to watch yourself around machinery.

    Back when I was in highschool there was a fad of writing the Goatse URL everywhere (the http://www.goatse.cx). The sheer disgust of the image was played up, yet it was never described. The frenzy got so bad that I went out of curiosity, only to be severly underwelmed.

  20. TwoHedWlf Says:

    Heh, Your GF's family reminds me of when my dad was telling my brother's Fiance about how he lost his fingers in Iraq. (None cares moment coming) She mentioned, "I've never heard what happened to your fingers?" So he told her, "Well, I was in Iraq and I'd just picked up a 6 pack of coke. I was walking back to the barracks when I heard a bang. I felt my hand get all wet and looked down, saw blood and my fingers were gone."

    She said, "Oh my god, I'm so sorry, I didn't know!"

    Meanwhile my wife, my brother and I were trying not to laugh, despite every word of what he'd said being true.

    He just left out that he'd lost his fingers in a sawmill accident about 25 years before and one of the coke cans had exploded from the heat.

  21. kamikrae-z Says:

    At this point it's probably worth mentioning the Saw Stop circular saw table. Definitely a clever design, although I have no idea whether the Saw Stop products are widely used or liked in industry.

  22. pywaket Says:

    In the hobby shop at MIT, we just replaced one of the two tablesaws with a SawStop saw. I have to say, I was doubtful that a new saw could be nearly as nice as the ancient Unisaw that it was replacing (my own preference is for staionary power tools that are older than I am - my home saw is a 1939 unisaw), but in fact, it is quite nice. Very precise settings and smooth feel.

  23. Daniel Rutter Says:

    Yeah, they're apparently perfectly good, though quite expensive. You have to replace a substantial assembly if the emergency-stop thing ever fires, though. The brake goes BAM onto the blade and ruins it, as in the old story about the hard-disk emergency stop system, and then you need a new brake cartridge ($US70) plus a new blade. Which isn't much compared with the initial purchase price, but I don't know if that's a good thing or not :-).

    The brake is apparently very unlikely to fire by accident because someone's just cutting wet wood, though it of course will if some kid decides to try the hot-dog test for himself. And it will also fire if you cut something conductive. There's a bypass switch to let you disable the safety system, which you have to remember to press.

  24. Stark Says:

    Having seen first hand the damage a table saw can do to a human hand in less time than it takes to blink... $70 for replacement brake plus cost of a new blade is cheap by comparison. I worked in a cabinet shop for spending cash while in high school and got to help a coworker find the three fingers he removed at the second knuckle. He was not exactly a safe guy - never used feather boards or push blocks. He was pushing some trim piece or other through the saw and sneezed violently - et voila, 3 less fingers. A bit traumatizing to the 16 year old me - especially digging out a finger from behind a lumber rack against the wall (a good 5 meters away) spotted by the bloody mark on the wall above the rack. A surgeon managed to re-attach 2 of the fingers, but obviously they never worked quite right after that. A Saw-Stop would have been a nice thing to have back then... of course, this is the kind of guy who'd probably just bypass the damned thing all the time... we was, after all, already missing most of a thumb and the pinky finger from the opposite hand. Not capable of learning a lesson I guess.

  25. Alex Whiteside Says:

    Getting back to magnets for a second, Steorn (of Orbo fame) are now selling a bunch of devices for measuring magnetic fields and (apparently) the torque generated by them (how the system miraculously subtracts all non-magnetic torques from its measurement is a mystery but presumably adds a lot to the price). You can attempt to buy them here.

    Either they've genuinely realised that the Orbo is bunk and are attempting to recoup their losses by selling gizmos they developed to test it, or their goal all along was to make themselves the magnet engine quack's equipment supplier of choice.

  26. Alex Whiteside Says:

    (They also sell a bunch of other crap to enterprise. Low-friction magnetic bearings, eh? Those might be useful in convincing people that a simple plastic wheel was a perpetual motion machine.)

  27. bbot Says:

    Magnetnerd.com seems to be dead.

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