Magnetized blade?

nelsonmc

nelsonmc

Joined
Jan 14, 2005
Messages
1,225
I was sharpening my Kershaw Chive today and I noticed some iron filings were sticking to the edge. Well now I guess it is somehow magnetized cause I can pick up a screw with it. This ever happen to anybody here? Is there a way to demagnetize it? Thanks!

Edit: I just checked and the whole knife is magnetized, not just the blade like I thought.
 
It's entirely possible that your knife has become magnatized.

There are several ways you can possibly cure it. The first would be to drop it on a hard surface. A sharp blow often disrupts mild magnatization. This can be very handy to know when you have a screwdriver that's become mildly magnatized not so much as to be useful, but just enough that dust and filings and such annoyingly cling to it.

For a knife, though, you may not want to take this approach. The answer then is to expose it to a strong oscillating magnetic field. You can get a tool at Radio Shaft called a tape head demagnatizer that produces such a field and that can probably demagnatize your knife. A bulk tape eraser (which may also be available at Radio Shaft or look on eBay) will probably also take care of it.

But, here's an even less expensive idea that should work if the knife isn't strongly magnatized. Wrap the cord of a 100W or so lamp around your knife taking care that the blade won't cut the cord (not a problem with folders but I mention it in case of fixed blades). Leave the lamp on for an hour or so and the oscillating field will demagnatize your knife.
 
Thank you very very much! I'm going to try the lamp cord idea right now. How does something like this happen? What could have magnetized it? It's a real pisser because I've been filing a knife and all the filings are sticking to this Chive like glue and I'm going to have to take it apart because they're in every possible little crevice.
 
Gollnick said:
...Wrap the cord of a 100W or so lamp around your knife taking care that the blade won't cut the cord (not a problem with folders but I mention it in case of fixed blades)...
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Gollnick,

Have you done this and verified it? I never have, but I would think wrapping the cord around the blade would cancel out the magnetic field: you would want the sine wave to oscillate positive one way, negative the other. By wrapping the cord, the portion of the cord would cancel out the effect, no? This is a common approach to cancelling magentism in current carrying wires (curling or twisting along the wires' length).

I would advise laying knife blade on top of and parallel to the power cord.

But again, I have *never* done this, so could well be entirely wrong. :confused:
 
Well when you take a piece of wire and wrap it around a nail and hook a battery to that wire it makes a electromagnet right? I remember doing that in school once or twice. I guess now I'm wondering if wrapping the cord of a lamp (around metal) would do the same thing and if so how would making an electromagnet demagnetize something? I have a big 250lbs magnet that I've stuck screw drivers to and they become magnetized but only for a short while. I really don't want to drop the knife like a tool. Oh well, it's still wrapped in the lamp wire, we'll see if it works a bit later I guess.

If it doesn't work I'll try laying it parallel to the power cord too.
 
Definitely let us know.

If it works, that's definitely a cool way to demagnetize something.
 
Well when you take a piece of wire and wrap it around a nail and hook a battery to that wire it makes a electromagnet right? I remember doing that in school once or twice. I guess now I'm wondering if wrapping the cord of a lamp (around metal) would do the same thing and if so how would making an electromagnet demagnetize something?
Click to expand...

When you made an electromagnet in school by wrapping wire around a nail you got the electricity from what? Probably a battery! That's DC.

Household electricity is AC. It changes direction sixty times per minute (fifty in Europe).

When you wrap the cord around your knife you are, indeed, creating an electromagnet with your knife at the center. But, because this electromagnet is fired by AC current, the polarity of the maganet (north pole vs. south pole) will change 60 times per second (fifty in Europe). And that's what has the effect of demagnatizing the metal.

This technique works for items that have become mildly magnetic.
 
You know, I should know the difference between DC and AC, considering I went to college for get this... Electronics Engineering! :D :eek: :rolleyes:
 
You make a coil out of the lamp wire then slowly witdraw the knife from the center of it, that way you have a diminishing oscillating field, way more effective.

TLM
 
Depending on the knife, it will still hold mildy magnetic to whatever pole it was when you cut the power.

If you have an CRT monitor with degaussing on startup you could put the knife neear or on top and cycle the monitor a few times. Magnetic work holds are often used in manufacture of steel parts, could beleft over from manufacturing process.
 
DaveH said:
Depending on the knife, it will still hold mildy magnetic to whatever pole it was when you cut the power.

If you have an CRT monitor with degaussing on startup you could put the knife neear or on top and cycle the monitor a few times. Magnetic work holds are often used in manufacture of steel parts, could beleft over from manufacturing process.
Click to expand...


I'll try the degauss next lol! Anyways, had the knife since early 2004 I think and it just recently desided to magnetize itself. I have no idea how it happened but it sure as hell annoys me.
 
The lamp cord will be conducting 60 cycle per second alternating current (AC). That means that you will indeed make an electro-magnet, but that magnet will be flipping directions every 120th of a second. The net effect is that it will flip-flop the magnetic domains in the metal so much that you will tend to eliminate residual magnetic fields.

Those are the generalities; there are a few things that will improve how this works. The first issue is that lamp cords are a type of twin-lead cable. There are two conducting wires attached side-by-side. The current in the two wires runs in opposite directions and tends to reduce or cancel the magnetic field coming out of the wire pair. What you really want to do is carefully split the wire down the middle (without exposing any copper) and make some loops using just one of the wires. It is best if you don't wrap the wire around the knife lengthwise unless you have a lamp dimmer switch on the lamp. That is because when you turn off the lamp the current will be running in a particular direction when it is stopped. The knife will sort of remember the last way that the magnetic field was oriented when the power was cut. It is better to slowly reduce the current (such as by using a dimmer switch) as you turn off the power. A better approach is if you have several loops of wire that are detached from the knife. This you can slowly draw away from the knife to taper off the oscillating magnetic field. It would really be nice if you had a coil big enough to surround the knife crosswise instead of around the axis of the knife. Residual magnetism will be less noticeable if it is not along the axis of the knife.

A professional degausser is usually a big loop with a lot of turns. You activate it and slowly wave it around and over your magnetized object. Then you slowly draw it away before turning it off.
 
Whoa what the hell? I just tried the degauss a few times but holy crap the knife is wicked magnetized now for some reason. I can lift another knife with it now. Somebody told me to rub it on another magnet... Could that work?

Haha here's a picture of a T6 torx stuck to it along with some iron filings which you can't really see, damn knife.

magneto.jpg
 
Your monitor spends most of its time with magnetic fields oriented in a particular direction. You are likely to magnetize your knife more with your monitor. Rubbing your knife with a magnet has similar risks of increasing the magnetic field rather than reducing it. At this point maybe you want to call around and see if there is a computer repair store nearby that will use a commercial degausser on it for you.
 
knife is wicked magnetized
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oops. I guess that's why I don't demgnetize knives for a living. :footinmou

OTOH, maybe you could sell it on ebay as a sepcial survial tool. Include some thread to suspend it by and have a combined knife/compass.
 
Haha wherever my knife is so is North according to the compass I got right here... Oh this is sweet, real real nice. Haha it works up to a foot away.
 
I'm sure in a few weeks Dark Ops will be running an add for their super magnetized blades...... :(
 
Used to disorient and affect the enemies directional finding ability.
 
FIXED! -- I took the knife apart so the plastic pieces were safe then I heated up all the metal parts to about 200F and then let them cool. No more magnetism! Found this little trick through lots of google searching.
 
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