Magnetism expectations in knives

[thebradleycrew]

Hey folks, curious for my own education on this one. I noticed the other day, in using two carbon steel knives, that there was a small magnetic attraction between them. Lo and behold, I found that to be the case in a couple of my knives. Now, I keep most of the ones out on a magnetic block(s) of some types, and curious if or how there could be attraction between them or if using a magnetic block in some way impacts it or if it is austenite or cementite related. I"m sure some folks like @Troopah_Knives or @MSicardCutlery or @Larrin can assist! Thanks!

 

[M1k3]

Leave the knives on magnets long enough, and they'll become magnetic. Degaussing will demagnetize them.

https://sharpyknives.com/why-is-my-knife-blade-magnetic/

 

[noj]

Hey folks, curious for my own education on this one. I noticed the other day, in using two carbon steel knives, that there was a small magnetic attraction between them. Lo and behold, I found that to be the case in a couple of my knives. Now, I keep most of the ones out on a magnetic block(s) of some types, and curious if or how there could be attraction between them or if using a magnetic block in some way impacts it or if it is austenite or cementite related. I"m sure some folks like @Troopah_Knives or @MSicardCutlery or @Larrin can assist! Thanks!

I don't have those answers, sorry, though I would guess you would need to add higher (than room) temperature to have those effects.

If you don't mind adding to your thread, I was curious if the magnetism affects polishing.

 

[noj]

Leave the knives on magnets long enough, and they'll become magnetic. Degaussing will demagnetize them.

https://sharpyknives.com/why-is-my-knife-blade-magnetic/

Oops, overlapping post.

The article said (among lots of things): ".. this is undesirable as the now magnetized blade may collect magnetic filings, which can pick up dust and grit, making finishing difficult."

Though feedback from folks here welcome of course!

 

[Troopah_Knives]

Moving ferrite/martensite through magnetic fields makes them "permanent magnets". If you think of all the electrons in the steel as tiny magnets the magnetic field they are exposed to aligns the magnets and makes the steel magnetic (for an interesting read look up "magnetic domains"). In knives clad in austenitic steel, this effect is less noticeable because the cladding can't be magnetized (they also don't stick well to those boards which is kinda a pain)

This effect is very noticeable in the shop for anyone who uses a surface grinder with a mag chuck as after surface grinding all of the swarf stays stuck to the blade. I demagnetize my blades periodically when I work on them to keep them clean. You can get a demagnetizer for like $80 on Amazon IMO its pretty worthwhile.

 

[blokey]

When 2 knives really love each other….

 

[M1k3]

When 2 knives really love each other….

They make a Paring knife.

 

[thebradleycrew]

When 2 knives really love each other….

I felt this today. It was a @martinhuber making love to my @DevinT so it was sort of a weird child they produced.

 

[thebradleycrew]

Moving ferrite/martensite through magnetic fields makes them "permanent magnets". If you think of all the electrons in the steel as tiny magnets the magnetic field they are exposed to aligns the magnets and makes the steel magnetic (for an interesting read look up "magnetic domains"). In knives clad in austenitic steel, this effect is less noticeable because the cladding can't be magnetized (they also don't stick well to those boards which is kinda a pain)

This effect is very noticeable in the shop for anyone who uses a surface grinder with a mag chuck as after surface grinding all of the swarf stays stuck to the blade. I demagnetize my blades periodically when I work on them to keep them clean. You can get a demagnetizer for like $80 on Amazon IMO its pretty worthwhile.

This is helpful. Definitely ordering a demagnetizer! Thanks, Malachi!

 

[MSicardCutlery]

Well....I have to watch this thread now just to see what Martin has to say to that

 

[thebradleycrew]

I can’t separate them.

 

[M1k3]

I can’t separate them.
View attachment 285728

#MenageATrois

 

[tostadas]

I can’t separate them.
View attachment 285728

 

[stringer]

I don't have those answers, sorry, though I would guess you would need to add higher (than room) temperature to have those effects.

If you don't mind adding to your thread, I was curious if the magnetism affects polishing.

I'm not much of a polisher but I can tell you that a highly magnetized knife gets annoying when doing general sharpening. Bits of swarf are magnetically attracted to the bevel. It can be especially noticable when doing tip work.

 

[brimmergj]

Bits of swarf are magnetically attracted to the bevel. It can be especially noticable when doing tip work.

I've had this happen a few times, but never thought about magnetism. Next time I'll check with a magnet.

 

[Troopah_Knives]

I can’t separate them.
View attachment 285728

Jeez at least put up an NSFW tag if you are gonna post something like that

 

[HSC /// Knives]

Moving ferrite/martensite through magnetic fields makes them "permanent magnets". If you think of all the electrons in the steel as tiny magnets the magnetic field they are exposed to aligns the magnets and makes the steel magnetic (for an interesting read look up "magnetic domains"). In knives clad in austenitic steel, this effect is less noticeable because the cladding can't be magnetized (they also don't stick well to those boards which is kinda a pain)

This effect is very noticeable in the shop for anyone who uses a surface grinder with a mag chuck as after surface grinding all of the swarf stays stuck to the blade. I demagnetize my blades periodically when I work on them to keep them clean. You can get a demagnetizer for like $80 on Amazon IMO its pretty worthwhile.

Yes, a surface grinder magnetic chuck makes the blade magnetic