Big freakin magnet!

[wierdscience]

http://cgi.ebay.com/6-dia-x-2-neodymium-magnet-magnets_W0QQitemZ7504085602QQcategoryZ1267QQcmdZViewItem

I guess this where "watch your fingers" comes into play

[darryl]

Yeah, watch your fingers squirt out all over the room. That would be a considerable annoyance. Might be best to only get one. Best to keep an eye out for the mailman, you'll find him pinned to your mailbox.

[Frank Ford]

Yoiks!

It seems borderline irresponsible, let alone actionable, to sell a 45 strength monster of that size to the public. I regularly use a 36 grade 2" diameter by 2" long cylinder, and it's a brute I wouldn't approach unless it's in its cage:

http://www.frets.com/FRETSPages/Luthier/HighTechDept/Magnets/MagPlunger/magplunger.html

[darryl]

That was my first thought, that it probably shouldn't be sold to the general public. Then I thought what if you wanted to pick it up yourself and save the shipping costs- how would you get it past the steel door jambs of the car without having an - incident. Do you remember to leave all the cassettes at home, along with your credit cards? Which machine in the shop do you want to become a permanent part of- cause if that magnet wants to unite with the machine and you're in between, there you are.
I'm trying to think of a good use for maybe forone of those monsters in the shop-

[Evan]

http://mripractice.tripod.com/mrpractice/id69.htm

[rockrat]

Nice link Evan. The compressed gas bottle in the MRI looks scarry.

Is there not a material called moo-metal that they use to ship magnets with? I seem to recall a fellow telling me about the stuff.

[cuemaker]

Ok, i obviously dont understand the strength of the magnet.

If i was holding it near my lathe, how far away would I be when I started to feel its tug?

And what are the uses of such a magnet?

[Oby1]

WHAT is MOO-metal,tell me more
Bob

[BillH]

Hmm, buy a whole bunch of them, you could make one hell of an outrigger brushless motor.
For some reason, does any one else feel like it would be fun to do tests on computers with that magnet?

[Wirecutter]

<font face="Verdana, Arial" size="2">Originally posted by Oby1:
WHAT is MOO-metal,tell me more
Bob</font>

I think I can sort of answer this one. First, I've always heard it called mu-metal (meYOO metal).

I've worked with mu-metal as a magnetic sheild. I was told it's made by taking a (I believe ferrous) metal and grinding it up into a powder. Then the powder is pressed back into metal sheets somehow. You wind up with a metal sheet with absolutely no "grain", and you can't develop magnetic eddy currents in the metal. So it winds up being a magnetic shield.

The biggest downside is that it's so expensive. I don't know how effective it is, either. At work years ago, we were trying to shield data aquisition instrumentation from picking up H-field stuff (magnetic crap) from a nearby induction furnace, and it was a real bitch. Mu-metal was used, but it wasn't the only technique we needed.

Is there a metallurgist or chemist that can clarify this explaination here?

-M

[japcas]

I wouldn't even want to get near that magnet and definitely not between it and a piece of metal. We have some 1/4 by 1in. by 2in. neodymium magnets at work we use with our wire machine to hold parts after they are cut loose from dropping on the lower head. I think they are rated at about 110 lbs. of pull and they will pinch your fingers in a heartbeat. We don't use those that often as we usually don't need that much strength.

[Frank Ford]

The neodymiums in the 2 x 2 inch size are used extensively in band instrument repair. You toss a steel ball of appropriate size down the bell of the horn, and rub the outside with the magnet. Like magic, the dents are ironed out of the brass from the inside. Quite a sight!

There are lots of injury reports, particularly when mechanics forget the strength of the magnet, and carry it to the workbench, only to have screwdriver jump and punch a hole in the back of a hand.

[hoffman]

<font face="Verdana, Arial" size="2">Originally posted by cuemaker:
Ok, i obviously dont understand the strength of the magnet.

If i was holding it near my lathe, how far away would I be when I started to feel its tug?

And what are the uses of such a magnet?</font>

I played with one that was about 1/4 square and about 3/8 long. I could not pull it off the fridge and had to slide it to the edge and pry it off. It was one hell of a magnet! I can't even comprehend the strength of one of those big ones.

Based on my experience with a little one I imagine that big sucker could send you to the emergency room :0 Especially if 2 of them popped together...

I was wondering about shipping. Surely they couldn't ship that thing by UPS!



------------------
Deep Sea Tool Salvage

[darryl]

Mu-metal is a nickel iron alloy that has a superior ability to conduct a magnetic field. It is easier to magnetize and has lower losses than ordinary steel. Apart from that there's no magic about it. If the magnetic field strength is more than a certain thickness of material can contain, then there will be leakage flux. It's no different for mu-metal. Permalloy is another name for a nickel iron alloy which exhibits better performance in handling magnetic field strength than typical transformer lamination material. A newer development, some years old now however, is a fast quenched alloy that is better at containing a magnetic field than ordinary transformer steel. It comes down to how much thickness of material does it take to prevent any magnetic field from escaping the confines of the device. Ordinary steel will do the job, but a greater thickness will be needed than if nu-metal is used. Other factors come into play as well, such as frequency of the magnetic field signal, and the degree to which the shielding material is completely wrapped. This is the same for all magnetic materials, nu-metal being only one of them.

If that large magnet is shipped with magnetic shielding around it, then the thickness of that shield material will have to be some minimum in order to not let any flux leak out. The further that shield box is from the magnet, the thinner it can be, but of course the size of the whole package is greater then too. If the magnet came with a keeper, like the old horseshoe magnets, then that presents a handling problem which is how to get the keeper off the magnet. I'm wondering as well how they would prevent problems when shipping such a powerful magnet.

Of course, they could always be shipped air mail. The receiving end would have one of the magnets, and the shipped magnet would just be launched in the general direction. I'm not sure how the receiving would be handled though. I can see it now- 'incoming magnet, RUN LIKE H---!

[Mcgyver]

this is interesting, but strictly abstract - i don't want one anywhere around my shop! how are they made? how they stored? what would you use one that powerfull for?