axe problems, badly tempered

[Peter_t]

hi there,
i almost finished fixing up an axe for a friend and was at the stage of fitting the head and thought i'd be better off reworking the blade first. i tried to use a file (brand new sandvik mill b*stard) and it just skipped over it like it was made of glass! no chance.

i wish i had tried this earlier! then i wouldn't have bothered fixing it but iv put too much work into it to abandon it now.

could i re-temper the edge a little softer? iv seen on greenpete's video when he tempers his knives by heating them with a blow torch until they turn a straw yellow colour. would it be easily done with an axe too?


many thanks!

Pete

 

[Ex Member lyndon]

unless you have a forge that can take an inch thick of steel to 800 degrees i woudnt bother trying your better off useing a mechanical form of stock removal IE. a grinder or belt sander just remember if you colour the metal you have removed the temper from it ...the file sliding off it like glass is a good thing
get a bucket of water and a belt sander stick it in a vice use 80 grit ot more if you have it finish with 240 or more but dip in the water after every pass as a rule of thumb ...dont use gloves if its to hot to hold its in danger of loosing its hardness

 

[Peter_t]

the file sliding off it like glass is a good thing

how is this a good thing? an axe that can only be sharpened with power tools is next to useless

i have got a home made forge and have heated a 4mm think file to neer white but i don't see the relevents to tempering the blade? correct me if im wrong but i thought tempering was done after hardening to take some of the hardness away so that it it becomes useable?

i have reprofiled many axes and none of them needed powertools.


pete

 

[robin wood]

Yes you are looking for around 200-220 degrees for tempering and it certainly can be done with a blow torch or over a domestic gas ring quite easily.

Tips

1 in order to see the colour you need to polish an area first easiest done with power tools and fine abrasives.
2 have a bucket of water handy because seconds after you see straw if you don't quench you may see bronze, peacock an blue by which time you are too soft.
3 be patient when heating and keep a close eye. It takes quite a while to start getting the heat up there and you will be watching for a couple of minutes with nothing happening then as soon as the colours come they can move quickly. The more gently you put the heat in (ie axe held further above the flame) the slower the colours will move when you get there but the longer you will have to wait.
4 with practice it is possible to pump a lot of heat in at first holding the blade in the heart of the flame then as it is getting closer to the temp you want letting it cook more gently.
5 if you go to deep straw or even bronze it will still be good for an axe.

 

[Jus_like_that]

Shouldn't be any need for a forge.

First of all, just set your kitchen oven to about 230 degrees celsius, put the bit in there for about an hour, you should see the colour change to deep straw. This is to normalise it. then let it air cool and try it then. after that you'll have no trouble sharpening!


ATB

Adam

 

[Matt.S]

Shouldn't be any need for a forge.

First of all, just set your kitchen oven to about 230 degrees celsius, put the bit in there for about an hour, you should see the colour change to deep straw. This is to normalise it. then let it air cool and try it then. after that you'll have no trouble sharpening!


ATB

Adam

Just a small point, this is tempering. Normlaising a piece of steel starts at critical/non-magnetic temperature (about cherry red glow).

 

[Peter_t]

just wack it in the oven? didn't think it would be that easy!

cheers guys!

pete

 

[Cegga]

Hi !!
If you only have to re- temper it put in you home owen and the temp 250 degree for 30- 45 min .
and this is to TEMPER it if you want to normalise it you have to do that in 580 degree for 5 hour but then you have to heat treat it again and the temp for that are 800 degree and cool it in water
cegga

 

[Dave Budd]

before you go retempering the head it might be worth rubbing the surface down with a bit of abrasive stone and then trying the file again. I often find with older axe heads that have a thick layer of rust/patina that a file has trouble biting to begin with. The heads are correctly tempered and are soft enough under the surface

 

[Peter_t]

what is normaliseing?

also 200, 220, 230 or 250? well my oven doesn't go to 250. is it the temperature that which the steel is 'cooked' rather than the time its cooked that determines the hardness?


thanks again

pete

 

[Peter_t]

before you go retempering the head it might be worth rubbing the surface down with a bit of abrasive stone and then trying the file again. I often find with older axe heads that have a thick layer of rust/patina that a file has trouble biting to begin with. The heads are correctly tempered and are soft enough under the surface

thanks dave, the head isn't actually that old and had little rust. its just your typicle cheep hardwear shop axe with the usuall forced on then glued head which breaks in notime .

pete

 

[Matt.S]

what is normaliseing?

also 200, 220, 230 or 250? well my oven doesn't go to 250. is it the temperature that which the steel is 'cooked' rather than the time its cooked that determines the hardness?


thanks again

pete

Normalising is similar to annealing in that it is a process whereby the structure of the steel is relaxed -- this removes stresses within the steel and softens it, though not to as great an extent as annealing does. Both processes start by heating the steel above the critical point -- around 8-900C, followed by slow cooling. The speed and medium in which the steel is cooled is where the two processes divide; annealling is often done in an insulating medium such as woodash or perlite, whereas normalising is faster -- leaving the piece to cool in still air is common. Normalising is not a complete relaxation/softening but is good enough as a prepratory stage to hardening. Neither of these processes are what you wan to be doing in this case.

No-one can tell you for sure exactly what temperature to temper your axe -- the precise steel composition is unknown, though it is reasonable to assume it's a plain-carbon steel with around 0.7-1% carbon. 220C is usually near the upper limit of what you can get with a domestic oven, and it will bring 1% carbon steel down to a useful hardness.

Temperature is the more crucial factor in tempering, but you must allow sufficient 'soak' time for the core of the axe to reach the same temperature as the outside. Because your oven is thermostatically controlled (and so you are unlikely to overtemper), an hour is a good time to be on the safe side.

 

[Peter_t]

thanks Matt.S
i'l give it a go tomoro and post the results


pete

 

[Cegga]

I am not 100 % sure but I say that sandvik use the Fundia steel as Gränsfors and the rest of the axe makers in Sweden use .And then the temp and time I write are rigth .
heat treat in 800 temper in 250 30 min get the axe ca 56 HRC .
If you want it harder you can go down on the temper temp 200 degree get ca 60 HRC .
Cegga

 

[bushblade]

Sounds like a whole lot of hassle on a cheapo axe to me. Just leave it as it is and sharpen it with wet and dry glued/taped to pieces of wood, don't use the file.

 

[ged]

how is this a good thing? an axe that can only be sharpened with power tools is next to useless

Depends on your situation. My axes live in the workshop, a couple of metres away from the bench grinder. If one needs sharpening its (a) very surprising unless the wife's been using it on concrete blocks and (b) it's about a 30 second job on the grinder. I don't need to shave with my axes. If I sharpen an axe once a year I think there's something wrong with me. I have wood burning stoves, and I chop up (or at least split) quite a bit of wood - about three or four tons per year. I don't do much felling and I use a chain saw for the bulk of the cutting.

If you aren't experienced in heat-treating steels I advise you not to try it on anything that you value. It's an art that takes a lot of learning, and you'll make quite a few mistakes on the way. A lot has been said about temperatures, but nothing about the atmosphere - the gases around the parts during heating/soaking/cooling. At high temperatures (more than you get in the oven) the atmosphere can rapidly combine with the iron etc. in the parts to make things like nitrides (hard) and oxides (nasty). You also have to consider the metal composition, the carbon content is vitally important, and nobody here knows what it is. As Matt.S says, you probably don't want to be doing that sort of thing. At very high temperatures if you quench with water you can get hydrogen released which is pretty good at combining with metals and that's very nasty - it can cause cracks which don't appear until much later when you stress the parts for example. That's why they need to control hydrogen in many welding operations.

I seriously doubt that your axe needs any heat treatment at all, and I'm quite sure that the handle won't benefit from it.