Magnetic Knives?

[cart@@n]

I discovered that some of my knives are slightly magnetized, the worst examples can hold a sewing needle on the blade.

This fenomena seems to be more prevalent in blades made in china.

Is it normal for blades to be slightly magnetic?

 

[Grease]

Heat treating a knife will de magnatize it. If it's magnetic, it's got s crappy/non existent heat treat.

One of the tricks for heat treating in a crude forge is to heat it until it's no longer magnetic.

 

[Grayzer86]

Heat treating a knife will de magnatize it. If it's magnetic, it's got s crappy/non existent heat treat.

One of the tricks for heat treating in a crude forge is to heat it until it's no longer magnetic.

That is incorrect on several levels. A properly heat treated blade can be magnetized just like none heat treated steel, and says nothing about quality. Also all steels lose their ability to ATRACT a magnet above roughly 1450 degrees, when the cool below that point, they will again attract a magnet.

 

[Grease]

That is incorrect on several levels. A properly heat treated blade can be magnetized just like none heat treated steel, and says nothing about quality.

Well, nevermind then. Apparently everything I've read about basic heat treating has been off...

Also all steels lose their ability to ATRACT a magnet above roughly 1450 degrees, when the cool below that point, they will again attract a magnet.

I think you mean magnets lose the ability to attract steel heated above 1450...

 

[spketch]

I've had good knives become slightly magnetic when working with a lot of hard drives in a given day. If you bring them near any strong magnets it can happen. Doesn't mean anything about the heat treat or quality of the blade necessarily.

 

[jmarston]

No, he means above that temperature, the crystal structure changes and the steel is no longer attracted by a magnet.

A couple of my blades are magnetic. My Strider is. Drives me nuts as I am a machinist and am always covered in chips and filings. Oh well.

 

[davek14]

Machinist here also. Many of my tools get slightly magnetic and pick up chips and metal dust. There are magnetic fields everywhere which can magnetize your tools. Electric motors and transformers put out a magnetic field. The big ones in a machine shop put out a big one.

We used to take junk hard drives apart to scavenge a powerful magnet from them.

When my daughter was in grade school she needed some iron filings for a magnet project. One way to get them is to drag a magnet on a string along the side of the road for a while. Well, I figured I could do that at work and get all she needed pretty quickly. I heard about "walking my magnet" for a while.

 

[dkb45]

I have a few knives that have become slightly magnetized. It means nothing about quality, they range from a few bucks to about $100. From what I have read and heard, it does nothing to the actual knifeocity of the knife, it just means it is magnetic. It still knifes as well as a normal knife knifes, it will just attract metal.

 

[Grayzer86]

Well, nevermind then. Apparently everything I've read about basic heat treating has been off...




I think you mean magnets lose the ability to attract steel heated above 1450...

I'm not trying to be a dick, just stating that the info was incorrect that's all. I DO heat treating, as well as read about it, and am also personal friends with several heat treaters, one of which does all of Kirby lamberts blades. I may not have been clear in my wording originally. A magnet will stick to cold steel, once the steel gets to that temp, (around 1450) a magnet won't stick, then When the steel cools, the magnet will stick again. That part is a proven fact. There is also nothing stopping properly or improperly heat treated steel from becoming magnetized itself.

 

[jla3156]

You could always demagnetize the blade.

 

[dkb45]

You could always demagnetize the blade.

Don't you most easily do that by the equivalent of a spine whack to knock the uniform molecules that cause magnetism out of alignment? I think swiping it over a magnet should work to, but that could have been made up by me at some point.

 

[Drew Riley]

Whacking the spine may demagnetize it to an extent. It could also ding up your blade!
Swiping it over a magnet will likely magenetize it more.

You can buy demagnetizer (also called degaussers by some) from Enco and other machinist supply houses. I think I got mine for about $45 on sale.

Just flip the switch, swipe the knife, tool, or what have you over the demagnetizer a couple times, and bada bing! Couldn't be easier.

As already stated, any knife, whether it's a $1 chinese special, or $1000 custom, can become magnetized for any number of reasons, independent of heat treat.
Some makers use magnets go hold blades while grinding. This is how mine usually get magnetized. Again, one or two swipes on my magic machine, and it's golden.

 

[liamstrain]

We have a magnetic knife rack in the kitchen - as a result, now most of our kitchen knives are magnetized too.

If it bothers you get (or borrow) a degausser.

 

[SPNKr]

Magnetic knife racks can cause that, but it's more likely caused by some powerful electronic device you may be around sometimes. The only possible issue I'm aware of are the filings that stick to the edge when sharpening, meaning it's a lot more difficult to get a clean and polished edge. As others have mentioned you can get a degausser.

Btw do not heat the knife till it's non magnetic unless you plan to heat treat it from scratch all over again. The Curie point is at a very high temperature (something like 900 degrees? can't remember) and you will get complete transformation to austenite.

 

[zzyzzogeton]

We have a magnetic knife rack in the kitchen - as a result, now most of our kitchen knives are magnetized too.

If it bothers you get (or borrow) a degausser.

This. +1 I have several machetes and large blade knives out in the shop that I "store" on a long magnetic "knife strip" that I got many years ago at a restaurant supply house. Every blade on it for any long period of time will develop a "magnetic personality".

 

[BenchCo Spydermade]

Whacking the spine may demagnetize it to an extent. It could also ding up your blade!
Swiping it over a magnet will likely magenetize it more.


As already stated, any knife, whether it's a $1 chinese special, or $1000 custom, can become magnetized for any number of reasons, independent of heat treat.

Nope. Not a ceramic knife. (Sorry, couldn't help myself)

 

[cart@@n]

Thank you guys for the answers.

I've been doing some research on the subject and it seems that a lot of processes can magnetize a knife, like machining, grinding, sharpening, polishing, welding, laser printing, among others.

I also saw companies offering demagnetizing services for surgical instruments to avoid contamination by eventual metallic particles attached to the instruments, being that one of the disadvantages of magnetized blades.

I wonder if carrying a magnetized folder in your pocket or holding it for long periods of time can have any negative health effects.

 

[zzyzzogeton]

Thank you guys for the answers.

I've been doing some research on the subject and it seems that a lot of processes can magnetize a knife, like machining, grinding, sharpening, polishing, welding, laser printing, among others.

I also saw companies offering demagnetizing services for surgical instruments to avoid contamination by eventual metallic particles attached to the instruments, being that one of the disadvantages of magnetized blades.

I wonder if carrying a magnetized folder in your pocket or holding it for long periods of time can have any negative health effects.

With all the electromagnetic radiation flying around from ground and air based radars, airplane altimeters, radio and tv stations, cell phones, microwaves, power transmission lines, etc, etc, etc...., a minute magnetic charge on a knife blade is the least of our problems.

 

[Rapt_up]

You can magnetize most magnetic steels by swiping or rubbing it in a controlled direction repeatedly.... Sound like anything we do with knives? Like Sharpening???



Its got nothing to do with quality of manufacture, although some of the cheaper steels magnetize more easily. This includes all plain carbon steels as compared to stainless steels.

 

[amg137]

I wonder if carrying a magnetized folder in your pocket or holding it for long periods of time can have any negative health effects.

Magnets have never been shown to have any effect, good or bad, on human health. Heck, some hippies even wear them because they think they have healing properties. That's bunk, of course, but you shouldn't worry about it one iota.