How to tell if annealed properly - file knife

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ahlangle

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Sep 16, 2015
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First time trying to make a knife and have some questions.
I tried annealing a 10" Nicholson double cut bastard file to a "red heat" with charcoal and fan in pit.
Stuck it in bucket of sand to cool for an hour but when cooled, how will I know if I annealed it correctly (other than breaking my hacksaw or other tools on it)?

Also, I planned on this being a full tang knife. Any suggestions for handle? Is cypress too weak?

I'll take any advice on the process as this is my first time and not trying to make anything fancy, just usable.
Thanks very much
 
Try drilling into it. With hard steel, this is will take forever and not work, but with soft steel, it should be a lot easier. Some other people will probably come on with better advice soon
And i've never heard of cypress for a handle
 
If it drills with regualr bits then you probably annealed it enough to work it. If it didn't work, try using vermiculite instead of sand. Oh, and is this a new file or a vintage one? The older ones were made better than. The new ones these days.

Cypress is a soft wood, and isn't too suitable for a knife handle. If you are looking for cheap, easy to find wood then you might want to try maple, walnut, or Oak.
 
When trying to drill into it, what type of bits should be able to get through it (what is a "regular drill bit")?
It is a new file.
If a magnet no longer sticks to it, what is that telling me? I forgot the trick with that.
Thanks very much guys.
 
ahlangle said:
When trying to drill into it, what type of bits should be able to get through it (what is a "regular drill bit")?
It is a new file.
If a magnet no longer sticks to it, what is that telling me? I forgot the trick with that.
Thanks very much guys.
Click to expand...
The magnet is for heat treating not annealing. Regular HSS metal drill bits should drill if its annealed properly. Also take another file and see if it removes material. If it does you're good. If not then you need to try annealing again.
 
This is getting a little technical, maybe a bit more than the OP was wanting to hear, but a file (hopefully it isn't case hardened but actual high carbon steel) has too much carbon to be using the slow cool ash/sand/vermiculite treatment. From what I understand, employing that slow cool will put carbides into grain boundaries, making for a very brittle steel. In order to get the carbides back into their proper position, a full normalizing will be needed.

To anneal properly, you'll need to know critical temperature, and thus the magnet can be very handy, especially with a charcoal pit set up.

There are tons of threads on heat treating files, you might do a search and look up some of that info. Without going into why and all sorts of technical jargon, but here is a quick "recipe" on how to proceed with your file, because you let it slow cool and now carbides are in the wrong place, but at least the file should be machinable. Go ahead and cut your bevels, get the shape where you want it, leave about .020" or .030" at the edge. All of the following heat treating should be done with some anti scale coating (not needed during tempering), but if not, just realize there will be a layer of decarb after you heat treat that you'll need to sand thru. The decarb layer is soft, it will be on top of the hard steel, so don't let that trick you into thinking you didn't heat treat right. Sand thru the decarb layer first, check your hardness with another file.
Normalize at 1600°f and let it air cool.
Thermal cycle at 1500°f and let it air cool.
Thermal cycle at 1400°f and let it air cool.
Harden at 1475°f with a short soak, 5 minutes if you can do that with your set up, quench in fast oil. Canola oil warmed to 130°f works well if you don't have a quench oil. Do NOT use motor oil or ATF.
Temper at 400°f twice, at least one hour each time.

The magnet trick is good to know. Obviously with a pit charcoal heat treat set up, nailing temperature is extremely difficult. Just remember that the magnet will stop sticking at around 1414°f-1425°f. You'll need to guesstimate your temps by using the magnet, then the color. Do this in low/no light.
 
Are you saying you heated until a magnet wouldnt stick? Or do you mean now that it is cooled a magnet still wont stick?
 
I meant I heated "until red hot" and cooled in bucket of sand. Magnet still stuck afterward.
I must have done it properly because I've been able to cut it easily now.
 
Ok that makes sense. I thought initially that you meant after cooling, the magnet wont stick, and that threw me WAY off haha.
 
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