Top all-time · #3335
K&J Magnetics
Company blog · kjmagnetics.com/bloghardwarescience
K&J Magnetics is the company blog at kjmagnetics.com, writing about hardware and science. Since 2013, 23 different Hacker News readers have linked it 29 times, most often “Can I erase sensitive data on an old hard drive with Neodymium Magnets?”. No feed was found, so read it on the site itself.
Too few sampled comments (18) to say how often HN recommends it.?
Why HN links it
HN readers link K&J Magnetics, a neodymium magnet supplier, for its blog posts and product pages on magnet physics, such as levitation, Halbach arrays, and hard drive demagnetization.
Summarised by Claude from a sample of 18 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Most-linked posts?
- Can I erase sensitive data on an old hard drive with Neodymium Magnets?3 people · 3 mentions · first linked 2017-12-03
- /blog.asp?p=diamagnetic-levitation2 people · 2 mentions · first linked 2023-07-25
- /blog.asp?p=electromagnetic-levitation2 people · 2 mentions · first linked 2019-01-22
- Neodymium Magnets FAQ2 people · 2 mentions · first linked 2018-11-18
What Hacker News says?
If you can find some N52 grade magnets it's worth ordering them just for the novelty value This 1013 lb pull N52 magnet could also be entertaining. Maybe also useful for checking grilled meat for metallic objects. https://www.kjmagnetics.com/proddetail.asp?prod=BZX0Z0Y0-N52...
Comment linking /proddetail.asp?prod=BZX0Z0Y0-N52&cat=168
on “Canadian surgeons urge people to throw out bristle BBQ brushes”Submitted Can Repelling Magnets Replace the Spring in a Pogo Stick? as a story · 292 points
HN discussionMaybe as "toy sets" of magnets; it seems there's a ton of back and forth. That said, you can get spherical rare-earth magnets here: https://www.kjmagnetics.com/products.asp?cat=12 ...though a set of such won't be cheap, depending on the size of the magnets wanted.
Comment linking /products.asp?cat=12
on “Senator asks FBI director to name the cryptographers who support backdoors”Submitted Can I erase sensitive data on an old hard drive with Neodymium Magnets? as a story · 105 points
HN discussionSeems like the tough part of this is access to the magnetizing machine. I wonder if the same effect could be achieved by placing tiny off the shelf magnets[0] in the molded part instead? [0] https://www.kjmagnetics.com/proddetail.asp?prod=D101-N52
Comment linking /proddetail.asp?prod=D101-N52
on “Show HN: Put this touch sensor on a robot and learn super precise tasks”Submitted Watching Magnets Rust as a story · 44 points
HN discussionThere are actually very powerful permanent magnets inside of every spinning hard drive already, so clearly there's more to destroying data than just having a magnet nearby. https://www.kjmagnetics.com/blog.asp?p=hard-drive-destructio... has a writeup about trying and failing to wipe a drive with extremely powerful magnets.
Comment linking /blog.asp?p=hard-drive-destruction
on “Recover HD Using a Magnet”Submitted Tensegrity Table as a story · 2 points
HN discussionI was surprised to read that the magnets weaken over time. I honestly thought permanent where really permanent, but according to a google search: > Neodymium magnets are the strongest and most permanent magnets known to man. If they are not overheated or physically damaged, neodymium magnets will lose less than 1% of their strength over 10 years - not enough for you to notice unless you have very sensitive measuring…
Comment linking /faq.asp
on “I have magnets implanted in my hands”Submitted Magnetic Poles Are a Myth as a story · 2 points
HN discussion- F2 · 2017-02-23
Halbach arrays are just a pattern or orientation of magnets that biases the total magnetic field to one direction.[1] Polymagnets are just magnets with a pattern of multiple north-south poles on one face. [2] At best you could have a Halbach array on a single polymagnet and have it be just as effective as individual magnets in the same pattern. Though for large scale applications there wouldn't be much point as you…
Comment linking /images/blog/halbachvsalt.png
on “Electromagnetic Levitation Quadcopter [video]” Submitted Can Repelling Magnets Replace the Spring in a Pogo Stick? as a story · 2 points
HN discussionK&J Magnetics gave it a try: https://www.kjmagnetics.com/blog.asp?p=induction-stove
Comment linking /blog.asp?p=induction-stove
on “DIY induction stove – Frying eggs with magnets”Submitted Neodymium Magnets FAQ as a story · 2 points
HN discussionAs you might imagine, others have encountered and solved this problem already with stick on high friction disks. They've also used cheap, steel cups to direct and strengthen the magnetic field: http://www.leevalley.com/US/wood/page.aspx?p=32066&cat=1,423... Also, I've used those nice shiny magnets in outdoor applications and can attest that they rust in fairly short order. But one might be able to address this by en…
Comment linking /products.asp?cat=164
on “Attach anything to anything with sugru and magnets”Submitted Testing Magnet Strength – K&J Magnetics Blog as a story · 1 points
HN discussionNo, digmagnetic of levitation requires multiple magnets in a halbac array: https://www.kjmagnetics.com/blog.asp?p=diamagnetic-levitatio... https://pubs.aip.org/aip/apm/article/9/10/101107/1061600/Pho...
Comment linking /blog.asp?p=diamagnetic-levitation
on “A Room-Temperature Superconductor? New Developments”Submitted Halbach Arrays II as a story · 1 points
HN discussionThe field is not static when energized. The hanging ones are not too hard to make with a Hall effect sensor and an electromagnet. This is a good explanation: https://www.kjmagnetics.com/blog.asp?p=electromagnetic-levit...
Comment linking /blog.asp?p=electromagnetic-levitation
on “Naïve Math: The Mendocino Motor and Earnshaw's Theorem”Submitted Eddy Currents as a story · 1 points
HN discussionPermanent magnets don't do much to hard drives[0]. Well, with a strong enough magnet, it will, but the magnet will mechanically damagethe internals before they affect the actual data. Anyways, it can't be a solenoid because solenoids are unidirectional. They actuate in one direction, and have a spring return in the other. The actuator in hard drives needs to be able to actuate in both directions, so they use a magne…
Comment linking /blog.asp?p=hard-drive-destruction
on “Watching Magnets Rust”Submitted Magnetic Grates as a story · 1 points
HN discussionJust so everyone is on the same page, static passive diamagnetic levitation is possible with materials like pyrolytic graphite. https://en.wikipedia.org/wiki/Diamagnetism https://www.kjmagnetics.com/blog.asp?p=diamagnetic-levitatio... ...and superconductors are usually perfectly diamagnetic.
Comment linking /blog.asp?p=diamagnetic-levitation
on “The First Room-Temperature Ambient-Pressure Superconductor”https://www.kjmagnetics.com/blog.asp?p=electromagnetic-levit...
Comment linking /blog.asp?p=electromagnetic-levitation
on “Ongoing compilation table of LK-99 reproduction claims”A couple of years ago someone built a model submarine with an actual MagnetoHydroDynamic drive: “Magnet Powered Submarine - The Hunt for Red October IRL!” https://www.youtube.com/watch?v=nFsiydplCtw The corresponding blog entry includes the STL files for 3D-printing the submarine’s hull: https://www.kjmagnetics.com/blog.asp?p=red-october
Comment linking /blog.asp?p=red-october
on “DARPA’s silent MHD magnetic drives for replacing naval propellers”They are used in these applications, typically very high grade, unless you're buying a legacy product line. In, say, a hybrid stepper the magnet is usually a wide thin round disc, sandwiched between two steel rotor lamination stacks. With the link below you can examine the BH curve and load line for a Ø20 mm N52 disc magnet, 2mm thick, at 20 degrees C. (It's not exact because this assumes a magnet in free space and…
Comment linking /bhcurves.asp
on “Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines”What about, say, Neodymium magnets? https://www.kjmagnetics.com/neomaginfo.asp What I'm asking is: are Neodymium magnets NOT used in these applications?
Comment linking /neomaginfo.asp
on “Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines”They absolutely are, especially as the motors get bigger. See for yourself at k&j magnetics: https://www.kjmagnetics.com/?gclid=Cj0KCQjwmICoBhDxARIsABXkX... Small ones are a few dollars, bigger ones are hundreds or thousands
Comment linking /?gclid=Cj0KCQjwmICoBhDxARIsABXkXlILq8MC5a5RR20bfP1afy1hQMQ_CRrdEa16nr6TNDLbujnwjEHBGEgaAuy0EALw_wcB
on “ZF makes magnet-free electric motor uniquely compact and competitive”Look for Yttrium-Barium-Copper oxide that superconducts when cooled with liquid nitrogen. This is "cheap" cooling that will never run out. https://www.kjmagnetics.com/blog.asp?p=superconductors#:~:te... .
Comment linking /blog.asp?p=superconductors
on “Absence of superconductivity in LK-99 at ambient conditions”
