neodymium magnets

[DaveC426913]

I've seen these things for sale on the web.

http://www.amasci.com/neodemo.htmlhttp://www.kjmagnetics.com/safety.asp

I consistently see the same claims:
- they can easily pinch skin, like with a pair of pliers
- they can shatter, showering you with high speed shards

Are they really that powerful? I mean, I have no reason to doubt the claims, but I find it hard to imagine something so small being so powerful. To pinch your skin like pliers would require a HUGE attractive force.

Anyone had any experience?

I'm tempted to buy some just to prove it to myself.

(Although my original idea has bit the dust. As a joke, I was going to buy several, and carve or draw dots on them and use them as dice, just to get a larf.)

"Yeah, that's hilarious Dave, now would you mind driving me to the hospital? I'd drive myself, but with only one working eye... well, you know...."

[Claude Bile]

Yes, I remember in 2nd year physics labs, getting them stuck together and it took us about half an hour to jimmy them apart. I've never seen them shatter, but they are VERY strong magnets, you really do have to play with them to believe just how strong they are.

Claude.

[Gokul43201]

Good NdFeB magnets are both very strong as well as fairly brittle. Please take those warnings seriously.

If you buy a set of NdFeB magnets, you'll find that they come with non-magnetic spacers between them (whose thickness depends on the size of the magnets). Without these spacers, it will be virtually impossible to take apart a bunch of magnets that are stuck to each other face-to-face.

I've had experience working with as well as synthesizing high strength permanent magnets. You DO want to be careful when handling them.

[josephcheri]

how can we measure the magnetic strength of a neodymium magnets ?

[DaveC426913]

This thread is 7 years old.

You can measure the force in any number of mundane ways. Hang one on the hook of a standard fish scale or force-meter over top of another. Measure the force of pull at a given separation.

[ROY56]

HEY GUYS speaking of samaruim cobalt magnet, i have just built away for magnets to turn in a circle on a rotor as in a motor. i have found something interesting, i built my rotor on a brass shaft & about a foot below i made a cam on the brass shaft. now i have built my rocker arms that work the magnets in & out in ORDERLY fashion. this is when i hit a wall, because my motor was running but i couldnt slow it down or speed it up. so i needed somekind of carberator. then it hit me my rotor was allready running full out. so all i can do is slow it down. so by taking some non-mag wormscrew and building away for me to retract my magnets slowly and slowing my rotor down. for the rest of my power and rpm will have to come from pulse-magnets