heat treatment question

[titanius anglesmith]

Hi all,
over the last few months i have managed to get hold of a few old sheffield steel files.I hope to have a go at turning them into knifes at some point.Now i understand that they need to be softned first.I understand that part.Then rehardened.I understand that part.Then tempered.This is the part i am not shure about.I will be using my domestic oven to do this,and an oven thermometer.Do i,
1 heat up and quench again
2 heat up and let it cool slowly in the oven
3 heat up and air cool.
Thanks in advance.
regards Chris.

 

[milius2]

That's a very good question Chris, I'm looking forward to hearing some answers on this one. I would go for air cool But that depends on experience I think. You should try different methods but quenching is not needed I think...

 

[HillBill]

If you are just talking about tempering, the all you do is heat it in the oven and let it cool. I air cool mine. No quenching after tempering. You could leave it in the oven if you wish, it wont affect it as the only way to affect the temper is to get the steel hotter than the temp you tempered it at.

You should be aiming at a temp between 220 and 250c for tempering files. I cant be more specific as i dont know the steel. This should give you a range of between 57 and 59RC.

 

[BeerHunter]

Apologies for jumping on the back of this, but how do you soften the file, to work it?

And the OP mentions hardening, and then tempering? What's the difference?

Many thanks

 

[HillBill]

To soften a file you heat it up until the steel loses its magnetism. Usually around 800c. Then you let it cool slowly. Its then annealed (softened)

Hardening, as its name suggests hardens the steel. In its fully hardened state steel is brittle. If you hit it against the edge of something it will likely snap.

Tempering is a process that comes after hardening, it brings the hardness down some, to add toughness to the steel.

 

[BeerHunter]

Thanks for that

 

[titanius anglesmith]

Hi all,
thanks for answering this for me.
Regards chris.

 

[mikew]

As you know, the files are already hardened. All you need to do is temper them, then grind them. You shouldn't need to re-harden. There is a well known American maker called Michael Morris who does just that with all his knives.

To temper I would start with 220 degrees four an hour, then put an edge on it and see if the edge holds up.

Personally I'd recomend spending your time experimenting with O1 steel though. You can buy enough steel for three knives or so for around £10 and at least you will know what type of steel you are using that way. It would be annoying to spend hours making a knife only to find out the steel was unsuitable.

 

[titanius anglesmith]

Hi all,
good advice Mikew, i realise that going down the file route is hit and miss.I have never done anything like this before.But i got the files for nothing, so i thought nothing ventured nothing gained.I will be treating this as a learning curve,just to see what happens, and what is involved.If it turns out ok, or not i hope that i will have learned something.
Regards Chris.

 

[mikew]

Sounds good to me

 

[Fat ferret]

I always anneal, shape, harden and then temper. If you just ground the file as it is it would take longer and unless you can keep it cool you will probably affect the temper. Annealing and hardening isn't all that difficult, here's what I do.

Anneal the file, leaf spring or whatever by chucking it in the wood burner and hoaking it out when the fire has gone out. You can do this outside if you don't have a wood burner. It needs to get properly orange and then cool slowly in the embers.

Your file should now be easy to file. If you can bend it in your hands it's probably case hardened and useless. Now you can file it into shape or use a grinder.

To harden heat it up to orange again and hoak out and quench in oil while still orange, vegetable oil is fine. Dunk straight in not at an angle to avoid warping.

I then temper with a blow torch. Working from the spine I only let the edge get straw coloured. If you decide it's too hard once you have finished the knife just put the handle in a can of water and temper a bit more.

 

[georann]

Ok heres a slightly different question for you knife making aficionados, I have a neck knife that was made from an old file by a guy on BB. It has no handle material, just the bare metal file which has been ground and polished so it is comfy in the hand whilst still file patterned. The problem is the handle is a bit too long so I want to grind/Cut the end down. To do this I'm assuming I don't really need to soften it, but would the temperatures reached in cutting it ruin the blade and require retreating? Its currently razor sharp!
I can post a picture of it if that doesn't make complete sense.

Thanks in advance
Dan

 

[lannyman8]

if its a short handle (being a neck knife a presume it is) it may get too hot, the only safe way is to be sure and take precations, wrap the blade and handle area not being cut in cloth and wet it with ice cold water, start cutting the handle, when steam comes off the cloth re wet it and carry on, that should protect the blade well enough for the temper not to be messed about with, as above it would have to be over 200 c to start messing with the temper... OR put the blade in a tin can full of water, the water should cover all the blade and as much of the handle as possible below the cut line required, then blow torch it until red/orange hot, leave it to cool in the water, the red bit will now be soft enough to cut with a hack saw and file to shape... all good....

regards.

chris.

Ok heres a slightly different question for you knife making aficionados, I have a neck knife that was made from an old file by a guy on BB. It has no handle material, just the bare metal file which has been ground and polished so it is comfy in the hand whilst still file patterned. The problem is the handle is a bit too long so I want to grind/Cut the end down. To do this I'm assuming I don't really need to soften it, but would the temperatures reached in cutting it ruin the blade and require retreating? Its currently razor sharp!
I can post a picture of it if that doesn't make complete sense.

Thanks in advance
Dan

 

[ged]

http://en.wikipedia.org/wiki/Tempering

 

[titanius anglesmith]

Hi all ,
i have just revisited this thread. Thanks ged for the link that you posted. i will read it through later.Also to everyone else who offered advice.
Regards Chris.

 

[Paddytray]

please forgive me if I sound like a berk .
I've brought some AISI TYPE - 01
it's 3mm thick and the Tempering advice reads .
550f.(290c) 1 hour per Inch of thickness.
so how long should I hold the temperature for ?

 

[Hog On Ice]

3/25.4 x 60 = 7.08 minutes would be my best guess but I know nothing about the reality of tempering

 

[Paddytray]

that's what I thought but I dont want to balls up my first attempt .

 

[Albus Culter]

please forgive me if I sound like a berk .
I've brought some AISI TYPE - 01
it's 3mm thick and the Tempering advice reads .
550f.(290c) 1 hour per Inch of thickness.
so how long should I hold the temperature for ?

I think that's as a minimum guide. Longer wont hurt so long as the temperature does not raise any further.

 

[Dave Budd]

most people will temper for at least an hour, despite the industrial standard being that per inch of thickness. It is better to leave it in for more time than less since you need to make sure that the steel has been at the correct temperature throughout. Domestic ovens fluctuate wildly, so if you put it in for 7 minutes then it may not have reached the correct temp at all, let alone through its thickness and for the 7 mins.

I use a specially built furnace and I don't start timing until the thing comes BACK to the desired temperature. If I put a batch of blades in there it can take half an hour before the thermocouple reads the tempering temperature (axes will take even longer). Once the temp is there I leave for at least half an hour, but normally a whole hour for the first cycle at least. Repeating the tempering ensure that you have reduced any retained austenite and have fully tempered, it also allows you to creep up on the desired hardness by testing after the first cycle at a lower temperature.