Blade Tempering

[Lodian]

I gave this a try the other weekend.
Had a fire then as the main wood burned down opened my knife and put the blade in the red hot slow burning coals, i attached the handle with metal wire to pull it and gloves jml 350 degree resistant gloves.
After around 6-8 mins i took the blade oout it was glowing red, i then started to work it on my sharpening stone until i had what looked like a good edge, then soaked it in water till i could touch it with my ungloved hand.
It raised a really sharp edge then i polisheed the black muck of with some metal polish.


Anyone else tried similliar?

 

[davep90]

think you will need a new knife

 

[JohnC]

Justy for clarification... was this an existing knife that you were re-tempering or a new blade being tempered for the first time?

 

[Ogri the trog]

I gave this a try the other weekend.
Had a fire...... opened my knife and put the blade in the red hot slow burning coals......
After around 6-8 mins i took the blade oout it was glowing red,...., then soaked it in water till i could touch it with my ungloved hand.
It raised a really sharp edge then i polisheed the black muck of with some metal polish.


Anyone else tried similliar?

I can definately say "No".
Not sure what you're trying to achieve there Lodian, if you had a working knife already, then you're likely to have destroyed it, if you're lucky it might be a temporary thing.
When a knife is made from scratch (very generally) it is shaped whilst in a soft state, then hardened by heating it above a critical level, so that the carbon is absorbed into the steel, then quenched in oil or water. It is then in a hard state though very brittle - so it is "tempered" to trade some of the hardness for toughness. This is done by gently heating the blade to around the 180 - 220 degree Celcius mark (again generalised) and allowed to cool slowly.
By heating your blade, with no way of knowing the final temperature, you probably allowed the carbon to be released from the steel resulting in a very soft blade - giving the impression of being sharp by all the burrs that the stone would have caused.
You might be exceptionally lucky and be able to recover it but first we'd need to know what the knife started out as.....

My guess is you're in the market for a new one!

Ogri the trog

 

[weaver]

With all the warnings not to let steel get too hot while grinding you would think most of the people here know that placing a knife in a fire till it glows will certainly ruin the temper and will at the least require new heat treating to restore the hardness of the blade.

To be short about it, NO. Don't ever heat your knife like that.

 

[fredcraft]

I remember I did something similar on a machette I owned back when I was 15 y.o. ... good thing it was only a cheap generic model.

Of course, you cannot guess what it will do if you don't know about the process, so don't feel bad about it (unless it was woodlore or some other 300 quid knife..... was it ?! ). Lesson learned I guess !

 

[Lodian]

No it was a cheap £5 one but its still fine and i now find it easer to use when working with wood.

 

[C_Claycomb]

So to be clear...
You took a working knife. (Sheath knife? Folding knife? Stainless or carbon steel?)
Did you remove whatever handle it had on it?
You then put it in the embers of a camp fire, no forced air, not coal? Then let it sit there until it merely glowed red? You didn't check it with a magnet?

While it is glowing you use a sharpening stone on it?

Having had it cool some, to black? You then stuck it in water until it was back to room temperature?

You took it out of the water and polished the black oxide off the blade?

Have I got that right?

Even if I only have part of that right :yikes: Without seeing the result I don't want to say that you 100% knackered a knife, but I cannot see how that process could possibly improve even a £5 knife whether it was made of stainless or regular carbon steel. The sharpening while the blade is glowing sounds positively ridiculous...although that MIGHT not be what you meant, it just sounds that way.

What gave you the idea?

 

[Lodian]

Friend of a friend and i did magnet check it it was fine.

 

[C_Claycomb]

Were you trying to make it harder or softer?

If you checked that the blade was nonmagnetic at red heat it would suggest that you wanted the blade harder, which only works well with simple carbon steels, BUT, you must quench promptly from non-magnetic. If you drop below that critical point before quenching you won't get the blade properly hard.

Come on, having opened this can of worms you gotta be a little more descriptive

 

[Lodian]

Scared to due to some other posts, afraid the knife police will come and steall it from me lol and ban me from bying bushcraft knives in fututre.
Was aiming to make it harder. This was my first attempt and i was just having a stab in the dark(excuse the pun)

 

[C_Claycomb]

Well, you might get banned from buying anything that cost more than £10, but I reckon you will have no problem keeping hold of anything you decide to experiment on
There really is no need to dive blindfolded into knife making and knife modification. There are many great threads on here, on British Blades and Blade Forums about hardening, tempering, re-handling and all other aspects of knife making.

If you buy a Mora type knife you really don't need to make it harder. If you want something a little better than a Mora there are theads on here where folk discuss some of the good mid-range options like Helle, Kellam, the stuff that Tregor carry, Bruslleto and more.

If you want to try the hardening thing, look for O-1 tool steel, old springs, old carbon steel kitchen knives. Some will require nothing more than cutting out and grinding to shape (keep it cool), others need forging and the O-1 can be filed to shape, then heat treated by you, or one of the other members here on on British Blades.

Best of luck on your next project!

 

[JonathanD]

Scared to due to some other posts, afraid the knife police will come and steall it from me lol and ban me from bying bushcraft knives in fututre.
Was aiming to make it harder. This was my first attempt and i was just having a stab in the dark(excuse the pun)

Hey, don't worry about it, this is what blokes do. I'm always taking apart new stuff to see how it works. I remember when I bought a Rolex Submariner ten years ago the bezel was a bit rocky. Take it back to the shop? Nope, not me, popped it off with a SAK screwdriver blade and try to fix it myself. Worked too, thank God

 

[Lodian]

Lol got my mora the other day i aint letting it nere the fire i like it to much.