heat treating a knife

[brokenbiker]

right. after going through endless hunting knives over the last few years I have decided to make my own out of a file.

have even bought a brand new file for the job too, as it was only £1.20 on eBay.

anyway, the question is, will a go systems butane/propane mix blowtorch be enough to firstly anneal, then re-harden and then bring it up to temperature to temper the steel?

estimated max temp is around 1300 celcius and the nozzle is around 15mm dia and 30mm long. can produce a blue flame the dia of the nozzle and around 30-35mm in length on full flow.

will it do it just from holding the steel in the flame, or will I need some form of breeze block set up to keep the heat in?

 

[Pete.]

A brand new file might not be suitable as some are not through-hardenable. An older one might prove best.

 

[brokenbiker]

yeah came across that with the first one I bought. bought a second one that is suitable.

 

[julianthegypsy]

If you can get it up to a good orange temperature then it will be fine. You only need that to anneal it then harden it, tempering is much lower temperature anyway.

 

[brokenbiker]

yeah, I may have use of an oven on nights in work to temper but the annealing and hardening will have to be done in the garden.

would just use the propane but my torch is knackered after lending it (never lend tools!) to my brother.

will wait for the file to arrive then see what I can do. have some bricks lying around so may smash them up and use them anyway. cant do any harm

with a propane torch, does a bigger cup mean more heat?

 

[Bsmith]

with a propane torch, does a bigger cup mean more heat?[/QUOTE]

It will certainly mean more heat and more fuel use but not higher temperature.
Sorry BB I don't think that was the answer you were wanting.

 

[outofthefire]

Get a soft fire brick and make a small gas forge, that will maximise the heat from your torch.

 

[Wendelspanswick]

You could build a charcoal forge, either a truck brake drum or some insulation blocks, a blower (hair dryer or vacuum cleaner) and some lump wood charcoal.
If you use a vacuum cleaner as a blower you will only need to divert a proportion of the air otherwise you will blow the charcoal out of the forge, let the rest of the air vent out.
If you want old files go to a car boot sale, I can pick them up for pence.

 

[brokenbiker]

with a propane torch, does a bigger cup mean more heat?

It will certainly mean more heat and more fuel use but not higher temperature.
Sorry BB I don't think that was the answer you were wanting.[/QUOTE]

that was the answer I wanted, just worded the question wrong lol

what I meant to say was, does a bigger cup mean more temperature, but from what you have said it will just allow a larger area to be heated as opposed to a smaller cup

 

[brokenbiker]

You could build a charcoal forge, either a truck brake drum or some insulation blocks, a blower (hair dryer or vacuum cleaner) and some lump wood charcoal.
If you use a vacuum cleaner as a blower you will only need to divert a proportion of the air otherwise you will blow the charcoal out of the forge, let the rest of the air vent out.
If you want old files go to a car boot sale, I can pick them up for pence.

have seen this on youtube and was quite interested at the time, but read somewhere that lumpwood charcoal doesn't last long in a forced air forge?

something like 4 times as much needed compared to regular coal.

I can get hold of coal occasionally as my missus grandparents burn it in their house along with logs, but cant get hold of much

 

[julianthegypsy]

Use coke. You can get a bag of forge breeze for something like a tenner. That's enough to make dozens of knives, it lasts ages!

 

[the artfull-codger]

have seen this on youtube and was quite interested at the time, but read somewhere that lumpwood charcoal doesn't last long in a forced air forge?

something like 4 times as much needed compared to regular coal.

I can get hold of coal occasionally as my missus grandparents burn it in their house along with logs, but cant get hold of much

If your grandparents have a coal fire then all you need to do is have them get it going bright then put your file in & watch till it goes nice & red then bury it with the coals & ashes then leave it overnight to cool slowly,then you can do what you want with it before you harden & temper it,temper to red again & quench vertically in cold water & it'll be rock hard & brittle, polish it up & then temper as you say at work, I do mine in the rayburn overnight.

 

[PTvor]

There's at least one knife forum where they talk about making knives

http://www.britishblades.com

It might be worth checking out. I'd guess they're more likely to have a detailed knowledge of which types of steel are the best and how to go about it since they are enthusiasts.

 

[rustyoldford]

If your grandparents have a coal fire then all you need to do is have them get it going bright then put your file in & watch till it goes nice & red then bury it with the coals & ashes then leave it overnight to cool slowly,then you can do what you want with it before you harden & temper it,temper to red again & quench vertically in cold water & it'll be rock hard & brittle, polish it up & then temper as you say at work, I do mine in the rayburn overnight.

In cold water thats asking for trouble on something so fine ? engine oil would be far better but make sure you do it outside as it does flame up sometimes and smokes like hell ! leave it in the oil for a good couple of hours to fully cool. I used this un many small dies and punches when i was making small press tools. When annealing i used to clean the metal up so it was nice and clean and do not touch item with you hand making sure it is spotless and free from oil add heat until it goes a light brown colour then quench.

 

[the artfull-codger]

In cold water thats asking for trouble on something so fine ? engine oil would be far better but make sure you do it outside as it does flame up sometimes and smokes like hell ! leave it in the oil for a good couple of hours to fully cool. I used this un many small dies and punches when i was making small press tools. When annealing i used to clean the metal up so it was nice and clean and do not touch item with you hand making sure it is spotless and free from oil add heat until it goes a light brown colour then quench.

I can only speak from experience & I've never had any trouble with hardening this way with old files ,silver steel & guage plate,quenching in oil does not give the same hardness as water & brine makes it even harder but I allways use water then let the temper down to what the job requires,ie light straw for hardness but not to take shocks, up to blue/purple for springs etc.

 

[brokenbiker]

cheers for the info.

have given a bit of 5mm mild steel flat bar roughly the same size as the file a go over with the butane/propane mix blowtorch and after a while it did come up to cherry so im confident I will be able to harden the file again

 

[outofthefire]

Ideally quench it when its loose its magnetism rather than going by the colour because in different light situations what looks like cherry red can be quite different temperatures.

 

[brokenbiker]

yeah I knew about the magnetism, just wanted to check my torch would get it to around the temperature needed