Magnetised steel and heat treatment

Kermit

Kermit

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Ive exposed my tree beater to a rather brutal regrind session on the belt sander and the blade edge has become magnetised, its a rather weak magentic field but noticeable after I took it to manual sharpening and the filings clung on. Is this a sign that the heat treatment has gone to the cleaners or am I just being anal.

If so would I be looking at a butane torch and bucket of motor oil to rectify the problem or is that asking for further problems.
 
Without knowing what kind of steel it is, attempting a home made heat treat is probably not a good idea.

I have never heard of grinding a blade causing it to become magnetic but I don't know for sure if it is possible. Is there any way it could have come into contact with a magnet?

I would just use it and see how the edge holds up. That will be your best way of knowing if you messed up the heat treat. You can also take a file and see if it skates over the metal or bites in with a little pressure. Of course you could scratch the knife so don't go overboard.
 
The best I can do is guess, 440C, its one of Martindales machete's which really doesnt help the id process because all the sales blurb offers is 'hot rolled steel' or something to that effect.

Its no doubt Sheffield steel so, expect nothing too exotic.

The entire blade got extemely hot during the beltsand regrind and of course this was directly along the blade edge so, just wondered.

Thanks for the responce FLaMTnBkr.
 
I would think that, as long as it didn't discolor the blade, your HT is fine. Did any part of the blade change colors?
 
If it is a stainless steel you definitely don't want to attempt a heat treat yourself. If it was a simple carbon steel like 1080 you could probably get away with something yourself but you would need to temper it which you might be able to do in an oven if it fit. I think you would probably just end up making things worse though.

That being said, since it is a machete you will probably be ok. You don't want a machete to be real hard since you can come into contact with hard objects like rocks. You might have made the steel softer but for just general yard work I doubt you will notice a difference unless you are trying to get it shaving sharp.
 
Kermit said:
yes one particular area on the edge did begin to brown, :o
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That area probably has a temper problem now but I wouldn't worry about it on a machete. When it dulls just sharpen the area out without getting it so hot. I could very well be that the magnetized metal will become demagnetized just from the impact of using it. IIRC impacts can disorient the direction of the molecules enough to demagnetize it. Could be totally wrong though.
 
Magnetism has nothing to do with the temper. Just whack the blade on something hard, and it will no longer be magnetic.
 
SOLEIL said:
IIRC impacts can disorient the direction of the molecules enough to demagnetize it. Could be totally wrong though.
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Bill DeShivs said:
Magnetism has nothing to do with the temper. Just whack the blade on something hard, and it will no longer be magnetic.
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Never tried that, learn something all the time here on BFC. But I do know that you can magnetize a steel rod, for example -- or a knife of you actually wanted a magnetic one :) -- by pushing it into the ground at an angle towards the north magnetic pole, and giving it some hard whacks with a hammer driving it into the ground. FWIW I saw this same effect all the time when I used to shoot frequently at a range, which like many ranges faced north ... firing pins would become magnetic; potentially a big problem on certain guns like 1911's.

You can demagnetize at no cost with a an electric soldering gun, for small items just insert through the loop of the tip and slowly withdraw while the gun is on. For larger stuff, or more demagnetizing "oomph" wind a coil of wire the right size, 3-4 turns is good, and do the same.
 
FlaMtnBkr said:
I have never heard of grinding a blade causing it to become magnetic but I don't know for sure if it is possible. Is there any way it could have come into contact with a magnet?
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It happened to my knife, too, from grinding.
 
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