How to Heat Treat this Axe?

[Anvil_Fire777]

Hello,
First off, Hope everyone here had a wonderful christmas, i know i certainly did!
Anyway, i made an axe head out off a peice of old leaf spring (5160 as far as i know) and i want to know how to harden and temper it safley.



The only oil i have is used motor oil whic from past experiences, works qiuet well with knives. This axe head is a different story all together. it will mostly be a small carving/light chopping axe.
Can someone please give a detailed explanation of how i should do this? I understand the consepts of heat treating and have put some of them into practice (not axe heads though) so iam not a complete noob at it

Some help with this would be much appreciated. Thanks :)

[dablacksmith]

ide leave it as forged... it dosnt really need to be hardened for the use you want to put it to..

[CurlyGeorge]

I agree with dablacksmith. For what you will be using it for it shouldn't really need to be heat treated. Unless, of course you just want the practice. Then use your used motor oil, heat the axe head and quench. :D

[MattBower]

dablacksmith and Curly George may be right. However, since you asked, I'd heat treat it just like a knife, with two exceptions: (1) you really only need to harden the first inch or two behind the cutting edge; and (2) you'll want to temper somewhat softer than a knife edge. I'd take the edge to the bronze-brown range for starters and see how that works.

[Anvil_Fire777]

Yes, At the moment the steel is WAY to soft. I went to cut up an old floor board and ended up with a large nick in the blade from a 1mm nail. if the axe had a little hardness, there would be no nick in the blade. I gave a friend of mine a phone call last night and asked him about hardening this thing. Hes a professional blacksmith. He gave me 2 ways of doing it but ile run them past you guys. The first was to simpily heat about 1cm deep on the edge to an orange heat and quench whole thing in oil or water. He said that if it is too brittle, then put back in forge and get to orange heat again and quench quickly up until the black line then put in vice and rasp it until you get a bronze colour then quench in water.

Which should i try?

[pkrankow]

Yes, At the moment the steel is WAY to soft. I went to cut up an old floor board and ended up with a large nick in the blade from a 1mm nail. if the axe had a little hardness, there would be no nick in the blade. I gave a friend of mine a phone call last night and asked him about hardening this thing. Hes a professional blacksmith. He gave me 2 ways of doing it but ile run them past you guys. The first was to simpily heat about 1cm deep on the edge to an orange heat and quench whole thing in oil or water. He said that if it is too brittle, then put back in forge and get to orange heat again and quench quickly up until the black line then put in vice and rasp it until you get a bronze colour then quench in water.

Which should i try?

Yes. Both are good, simple, quick methods. The edge can be drawn softer by heating the eye to a black heat slowly and quenching the whole thing when the edge shows a darker temper color. This can help you soften the edge with either method.

Use a magnet on a thin wire to determine the temperature to quench from. You want to be slightly above non-magnetic. About 1500F.

Phil

[MattBower]

Don't quench your leaf spring in water. Speaking from personal experience, if it's 5160 or a similar steel, it will not like being quenched in water. A reasonably thin oil, like canola or peanut, preheated to around 130 F, is a pretty good quenchant for steels like 5160.

Your friend's second method is the one I'd go with if I were choosing between them, except I'd harden more than a centimeter of the edge. I'd go for more like 3cm. I personally like to oven temper, but lots of very good axes have been made the way your friend described.

[basher]

I would advise heating the edge and quenching in oil or heating the whole thing and quenching in oil . I would temper in a kitchen oven at 220 to 250 degc . or do the tempering as a seperate opperation .
the using residual heat in the un quenched blade to temper is a no no as far as I am concerned as it does not really allow for enough time for martensite to fully form at the edge before you temper.martensite formation is not instant and if you do not allow the blade to fully cool the transformation will happen after the residual heat temper and you could have untempered brittle steel at the edge.

[MattBower]

I would advise heating the edge and quenching in oil or heating the whole thing and quenching in oil . I would temper in a kitchen oven at 220 to 250 degc . or do the tempering as a seperate opperation .
the using residual heat in the un quenched blade to temper is a no no as far as I am concerned as it does not really allow for enough time for martensite to fully form at the edge before you temper.martensite formation is not instant and if you do not allow the blade to fully cool the transformation will happen after the residual heat temper and you could have untempered brittle steel at the edge.

I used to feel that way, and the metallurgy geek in me still does. However, there's a video on YouTube of one of the Gransfors-Bruks smiths heat treating an axe by edge quenching, then letting the colors run. Those guys have forgotten more about making axes than you or I will likely every know. So although that technique seems less than perfect, in theory, in practice it seems to be good enough to make very good axes.

[basher]

yup ......
if that is what they do they get good results , I have a few of there axes.
however in "my world" I like repeatability and that means temperature control and fixed time intervals .I get what you mean about the knife geeks attitude to it all ....however after 16 years at it the geek is stronger every day!!
there are more than just one model for good practice , But, if you want good results using "old" ways, then you need experience to back up the subtle nuances of those good old ways.
its all good use full (usable) information.

[MattBower]

yup ......
if that is what they do they get good results , I have a few of there axes.
however in "my world" I like repeatability and that means temperature control and fixed time intervals .I get what you mean about the knife geeks attitude to it all ....however after 16 years at it the geek is stronger every day!!
there are more than just one model for good practice , But, if you want good results using "old" ways, then you need experience to back up the subtle nuances of those good old ways.
its all good use full (usable) information.

Oh, hi, Owen. I didn't recognize your handle over here.

You're probably right. That technique can work, but making it work well may be a matter of lots of experience. To be fair, I'm shouldn't make it sound as if that's how G-B heat treats all their axes. It could be how they do it, but I don't know that. The video seems to be from a class that one of their smiths taught. So he could've done it that way to demonstrate a technique that's achievable for students working with simple setups, not necessarily because it's what G-B does on a production basis. (The guy also did the hardening in a coal forge and seemed to eyeball the temperature. No magnet, thermocouple, or other temperature measuring device in evidence. I suppose you can get away with that if you've done a few thousand of them. Not me. )

[KYBOY]

Well heres how wedo it. We make and sell a bunch of hawks and axes. We harden about an inch to a inch and a half of the edge. We normally use 1065, 1075,1095 and sometimes W-1 for the cutting bits. We use peanut oil heated to about 125*-130*..After hardening we clean the blade too bright with a 220 grit belt. Then we heat in front of the eye and run the colors..Taking the edge to straw with hints of purple..
Now we have done it this way more times than I could ever remember (multiple axe/hawks a week) and we seem to have gotten it down pretty good. Our customers love em' and come back to buy more.
Ive saw the same video and we do it the same way. Coal forge and all.

[Anvil_Fire777]

Thanks everyone.
i ended up heating about 1 1/4" of the tip to orange heat and quench in room temp used motor oil. this hardended it a good so i wiped the exess oil off and tempered it back by holding it above the fire until the oil was burnt off and i could just see hints of bronze showing then i quenced in same oil. The edge from what i know is perfect. its reasonably easily sharpened and holds its edge against Australian Hardwoods, let alone soft woods like pine that it is intended for. i got the axe to shaving sharp and cut through a 5 1/2" gum tree limb and it was not, from what i could tell, any blunter. Still shaved arm hairs. That Gum is Seriously hard.
I will post pics of the axe soon, when i have time.

Once again, thanks, this was certainly a learning experience for me.