How Powerful are Rare Earth Magnets? (knife content)

S

Scott Free

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Sep 15, 1999
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I've just completed a small fixed blade pocket knife. I am thinking about carry options and I intend to include a small rare earth magnet at the tip of the sheath to better hold onto the knife. I found the magnetic discs on ebay. They are 1/8 thick and 1/2 inch in diameter. The problem with powerful magnets is that they can damage electronics and credit cards strips. I know enough to keep my wallet separated from the sheath/magnet. And I read that I should keep these potent magnets away from computers, electronics and magnetic media. What does this mean though? Should I not where the knife while I sit at my computer? If I keep the sheath/magnet in my right front pocket, will it affect my watch as my wrist swings past it? How powerful is a 1/8" by 1/2" rare earth magnet, and just how far will I need to keep it from my computer and watch?

Scott
 
The only critical thing to keep the magnets away from are magnetic storage media. That includes audio recording tape, VCR tapes, floppy disks, and cards with magnetic strips on them. A magnet can also give you distorted spots on a computer CRT monitor screen (usually correctable by getting the monitor to do a degauss cycle--often just by cycling the power). The computer hard drives are magnetic media, but you are unlikely to damage them unless you pull the drive out of the computer and open them. DVD's and CD's are not magnetic so they are safe. Only old mechanical watches are at risk from magnets.
 
Out of curiousity I bot two N45 Neodymium-Iron-Boron, 1/4" x 1", plated disk magnets while at Blade West. Very interesting powerful attraction and repulsion with each other. To the point of danger. They can attract and collide with such velocity and force as to fling off a sharp cutting/piercing piece or pinch and crush skin, depending on their size and rating.

With one in my pocket I can carry most knives (or my huge keychain of gadgets) I have on the outside of my pants pocket, if I so desired. With a larger neo, 2"x1"x.5" N50, I could carry my double bladed axe that way. So if your pockets are full you have an option ;) .

I have not had any problems with magnetic media, video displays or watches. However, the cautions that come with these magnets are many. Keep them away from someone with a pacemaker, for example. http://www.kjmagnetics.com/safety.asp

On ebay, magnet master has my business. His literature, that comes with merchandise, is very helpful. If I was to get any more neo magnets they would be spherical so there is less chance of pinching and shearing when they contact each other.

The idea of using them in a sheath has strong appeal to me. I gave my son a Gerber hatchet with a knife held in the handle by magnetism. I understand, per the vendor at Blade, that they are of use in folding knives without springs.

All the best,

oregon
 
The interesting thing is, if you do crack one of those hard disks open you'll find they contain rare earth magnets inside. Old hard disks are a great source for these magnets. I'm a system administrator and I have the opportunity to take apart tons of them. I have the magnets stuck to surfaces all over my office as a result.

Basically, I wouldn't worry too much about wearing the knife while near your computer. Just don't stick it on top of the monitor or on floppy disks and you'll be alright.

Jeff Clark said:
The only critical thing to keep the magnets away from are magnetic storage media. That includes audio recording tape, VCR tapes, floppy disks, and cards with magnetic strips on them. A magnet can also give you distorted spots on a computer CRT monitor scree (usually correctable by getting the monitor to do a degauss cycle--often just by cycling the power). The computer hard drives are magnetic media, but you are unlikely to damage them unless you pull the drive out of the computer and open them. DVD's and CD's are not magnetic so they are safe. Only old mechanical watches are at risk from magnets.
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what exactly do they mean by "rare earth" bud nealy uses it in his sheaths, have always wondered "WTF"??
 
I think its the material they are made out of, rare earth magnetic material like neodyum instead of just a magnetised lump or iron. Rare earth materials can give a much stronger magnetic field than iron.

www.unitednuclear.com sell rare earth magnets too
 
Scott Ridgeway said:
I've just completed a small fixed blade pocket knife. I am thinking about carry options and I intend to include a small rare earth magnet at the tip of the sheath to better hold onto the knife. I found the magnetic discs on ebay. They are 1/8 thick and 1/2 inch in diameter. The problem with powerful magnets is that they can damage electronics and credit cards strips. I know enough to keep my wallet separated from the sheath/magnet. And I read that I should keep these potent magnets away from computers, electronics and magnetic media. What does this mean though? Should I not where the knife while I sit at my computer? If I keep the sheath/magnet in my right front pocket, will it affect my watch as my wrist swings past it? How powerful is a 1/8" by 1/2" rare earth magnet, and just how far will I need to keep it from my computer and watch?

Scott
Click to expand...

The 1/8 by 1/2 disks are powerful enough that you can probably not pull two of them apart in the direction perpendicular to the flat surface. You can, however, pull them apart by shearing, in other words slide one of them off the other and out of the magnetic field to separate them. Your idea might work if the magnet is mounted so the knife blade lays flat across its field and is "drawn across" the magnet rather than "lifted off" of it. They might still be too powerful though.

Be careful with those things. They can fly towards each other and shatter on impact or they can shear off pieces of flesh that get in their way when they are flying.
 
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