How to heat treat a file?

I got a great big file this week I want to use to make a razor out of. But of course the file is still hardened. Who can help me with what temperatures I need to get it soft enough to work with and for how long it would need to be at that temp?

And after softening and working the metal, what would the best temps be to harden again and what process? Oil cooling, air, water etc?

I can use a professional grade heating oven to heat so it's down to the degree and minute precise if needed.

Who could help me with some hard needed advise :)

Thanks.

Without knowing the exact steel it's made out of its hard to say what exact temp is needed. But as a basic, heat the file up so its a nice glowing orange (or about 1500 if using the oven) for a few minutes then let it cool slowly (annealing) this will make it soft enough to work, and if it still seems very hard, repeat.

As far as heat treating your probably looking at around 1450-1500 deg F for about 5 min then quench in oil would be my suggestion. And then around a 2 hour temper at 450, that should get you in the ball park of 59-61 HRC assuming its W2 or something of the like.

An old file would likely be a simple carbon steel. New files could be anything that has been case hardened only deep enough to have hard teeth then get thrown away (disposable economy and cheap!)

To anneal such a piece, heat to the 1500 F (800C) for five minutes then put into a bucket of ashes that cover the whole blade and let it cool down slowly overnight. Any insulator, like vermiculite, or similar will work as long as it doesn't burn. Then it should be soft enough to grind easier. Heat treatment is as mentioned above. If the blade hardens at all it's good steel. If it's the disposable kind of new manufacture, it won't harden at all.

Good luck.

If you dont have vermiculite or simiar, you can heat it to temp in the oven and then turn the oven off and let it cool in there. It may not be fully soft but more than workable if it is a simple carbon steel. To anneal stainless you can program the cooling of the oven, like 25 degree's per hour(specifics depend on the steel type) to correctly cool the steel. Having a ht oven greatly increases your chance for success.

For annealing I put a thick, flattened iron pipe in the fire, with one end closed off, and put my knives in the pipe.
I heat it until both the pipe and the knives are glowing orange, and stop the air flow feeding the fire.
the fire will die down gradually and the thermal inertia of the pipe will make sure it cools down really really slowly.
After that they are annealled.

i've had no trouble working files simply heated red and left to air cool for annealing.

of course, once shaped i heat them again, harden via quench, polish bright (to read your color) and draw back with controlled heat. ancient steel-working traditions. Just basics, but i'm making tools, not razors here.

Thanks for the input guys. Great info, helps a lot :)

Quote:

---

Originally Posted by WadePatton

i've had no trouble working files simply heated red and left to air cool for annealing.

of course, once shaped i heat them again, harden via quench, polish bright (to read your color) and draw back with controlled heat. ancient steel-working traditions. Just basics, but i'm making tools, not razors here.

---

For knives you want to anneal before quenching. It reduces the amount of warp you will get, as well as reduce grain size.

Quote:

---

Originally Posted by Bruno

For knives you want to anneal before quenching. It reduces the amount of warp you will get, as well as reduce grain size.

---

I found out that one the hard way...

Quote:

---

Originally Posted by shooter74743

I found out that one the hard way...

---

Make a long thin knife from O1, and then quench in icecold water :D
Did that once, just for laughs :)

Hi Shaggy,

The best method to establish the temperature to reharden at is by using a magnet. The steel will become non magnetic once the bottom end of the critical temperature zone is reached. If you go above this by around 200 degrees you will obtain the full hardness without the guess work. To soften the steel is basically the same without quenching. If you have access to a heat treating furnace you will be able to ring the steel up to temperature in it then allow it to cool in the furnace.

It's already been menioned that some files are only case hardened and it is a good idea to cut off a small test piece to save the heart ache of putting in a lot of work for nothing. This has happened to me nn the past.

If it does turn out to be case hardened it can be used for damascus projects down the track.

I hope this helps.

Keith.

Thanks for the info.

Yesterday I got another file from the same brand. I have an uncle who works in the metal industry and he is going to get me specific data on the metal composition and the way to soften and harden it to factory specs. The files I'm using now are tested this week at 70HRC, so that's pretty hard, but brittle. But I don't mind, the edge is so fine it should sharpen up nicely.

If you are going to heat treat it, you're not going to hit 70 HRc.
And that's a good thing. The adjective for a 70 HRc razor would be 'defective'.
Extremely brittle, and extremely hard to hone.

People here have honed razors at HRc 64 and 65. It's very tedious and time consuming, and has a high risk of micro chipping.
I don't even know how you;d get a file to 70 HRc using normal heat treatment methods. But even if you could, it would just mean you created a useless razor :)

I'll double up on that!!

I recently had a full hollow 440c blade that was around 61-63. I accidentally forgot to put it through its second temper cycle. It wouldn't get through one shave then the edge would be so chipped out it was like it was never honed. It took a little while to figure out what was wrong, but an additional temper cycle and now its shaving like a champ. I think (depending on steel and profile) that 57-60 is where its at as far as razor edges go!

HI Shaggy,

70 HRC is unbelievably hard. this would only be obtainable under very controlled conditions. I'd recommend quenching the blade in oil even if this steel turns out to be a water quench steel also. The cross section of a razor compared to a file as you can understand is significantly different and a blade would more than likely not survive a quench that violent.

a blade hardness of around 60HRC would give the best overall performance whilst keeping a measure of toughness to prevent micro chipping and accidental knocks on the basin ect. as previously mentioned.

I know that having a razor with 70hrc is much to hard/brittle. It should be in the neighbourhood of 60-63 now. The original files are 70hrc, the one I am doing now is hardend to that 60ish figure.

Just curious, how are you testing the hardness & coming up with conclusive numbers?

My uncle who gave me the files is a metalworker milling/turning etc. and has the equipment to test this, and so he did.

Quote:

---

Originally Posted by Shaggy8675

My uncle who gave me the files is a metalworker milling/turning etc. and has the equipment to test this, and so he did.

---

That is certainly very convenient. Most of us have to devise all sorts of tests to get some idea of what is happening.
A rockwell tester is something I want to buy some day.

Well, we come from a family of metalworkers here. Me, my uncles, my brother, nephews all got their feet in turning, milling, grinding, welding etc. So it has got it's perks ;)

Had the opportunity today to take a pic of the oven I am using. Does the trick ;)

http://farm3.staticflickr.com/2850/1...e0b6597f_c.jpg


http://farm3.staticflickr.com/2827/1...73c117ea_c.jpg


Oven is calibrated couple of times a year to very high tolerance.

That's fancy, should be able to get the exact HT you want...almost as absolute as salts.

Quote:

---

Originally Posted by shooter74743

That's fancy, should be able to get the exact HT you want...almost as absolute as salts.

---

Atmosphere requires some sore of scale prevention barrier like foil or paint-on refractory coating. The oven gets hot, you quench, remove said scale preventer and you're done.
Salts require playing with a very small scale volcano. A much higher danger/fun factor and no fiddling with foils and paint-on wait for it to dry crap. ;)

Thats why when i grow up i want to be like you mike! I am all guy &a the danger factor is like a bug to a bug zapper!

I'm so jelous. I used to operate ovens like that, but don't have access to them anymore. I have to resort to more primitive methods.

+1 to what mike has said about foil or another oxidisation barrier for use when heat treating. It saves a lot of work later cleaning up the material once hardened, and it will also reduce decarburisation during heating to a degree.

It's a small privilege I have in the work that I do. Having good ovens and small machines to help with the end result.

""Hi Shaggy, The best method to establish the temperature to reharden at is by using a magnet. The steel will become non magnetic once the bottom end of the critical temperature zone is reached. If you go above this by around 200 degrees you will obtain the full hardness without the guess work""

Reminds me of being at the Farmers Museum in Cooperstown NY ~30 years ago. Watching a blacksmith working on an old forge. I asked him how he knew when the metal was hot enough. Showed me using an old Cow Magnet. But then said: 'or you can do it the way the 'old timers' did': ...and ran the piece of hot orange bar across his palm!!! Said ' just about right'. I said 'What' and he did it again. Asked if it didn't hurt?? He said: 'No, you get use to it!!'
Still one of the darnedest thing I've seen!

Well, I know some of the old timers, and seen some others in action on youtube. They use the color as an indication. Not a single one ran the steel across his hands. That is a good way to need a rush trip to the ER with 3d degree burns.

Agree with you... But... that why I can still see him sitting there doing it. Twice. He said that the piece he was working on was a chisel and he was placing a piece of steel for the edge onto the iron bar.
Only thing I could think of is that he came close but never touch his skin.

The sticker says 3000 Celsius? Does that oven really get that hot? That is about Double the melting temp of steel.

I never tried it but it should be able to. We also work with ceramics and stuff, those have higher fusing points than steel. for instance Zirconium dioxide (ZrO2) has a melting point of 2700c I believe. But we don't use that ourselves.

Thanks for the info, I did not realize there were ovens that got that hot. Mine tops out at about 1200c.

Quote:

---

Originally Posted by JMJones

Thanks for the info, I did not realize there were ovens that got that hot. Mine tops out at about 1200c.

---

That is a normal value. The reason most ovens top out at that value is that if they go much higher, they have to take measure to prevent the oven structure from melting :)