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Blacksmithing and Metallurgy Hand-wrought manufacture of metal objects, extracting metals from their ores, or purifying metals and casting useful items from the metals.

Blacksmithing and Metallurgy

Annealing a File

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Old 05-26-2011, 06:44:49 PM
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John Hamilton John Hamilton is offline
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Default Annealing a File

Can I anneal an old Blackhawk file with an acetyline torch? If so, how? I want to forge it into a knife. Thanks.
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Old 05-26-2011, 08:02:38 PM
Tom Martin Tom Martin is offline
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Default Re: annealing a file

Heat the entire file to a bright red, and bury in ashes or sand until cool. That should do it, but it will have to be re-hardened and tempered to make a good knife.
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Old 05-27-2011, 12:04:47 PM
David Hughes David Hughes is offline
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Default Re: Annealing a File

I second what Tom sez. SLOW cooling from a red heat is annealing. RAPID cooling of an appropriate steel produces hardening. Annealing relieves hardening and internal stress produced by forging. Tempering reduces hardness and increases toughness. If you want to forge a file, just heating it enough to work it should be sufficient without an extra step of annealing. You would want to anneal it after forging. As a file is a high-carbon tool steel, I believe it has a narrow range of working heat and also has a narrow range of hardening temp (heating before quenching for hardness). Without tempering, file steel will be too brittle for a knife, and tempering is it's own can of worms.

I watched a local blacksmith make hatchets (tomahawks). He would hot-cut sections of old flat rasps, take a piece of mild steel, heat and bend over, sandwitch the rasp steel in the center, and forge weld it together. This produced a hard but brittle center for the edge, butressed by not-brittle cladding, the mild steel making the eye of the 'hawk. I envied his forge welding, my attempts have been miserable failures
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Old 05-28-2011, 04:28:19 PM
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John Hamilton John Hamilton is offline
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Default Re: Annealing a File

I have a tomahawk of this kind with the hardened blade. That's the way they used to do axes, chisels, etc.

Last time I heated a file and cooled it in sand I reheated it to red, struck it with a hammer and it shattered. I'll try again until I get it right. There are a lot of worn out files around.

Thanks for the advice.
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Old 05-30-2011, 01:14:27 PM
Pete Spaco Pete Spaco is offline
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Default Re: Annealing a File

Knife making is what you do AFTER you have learned to become a blacksmith, in my opinion.

There is red, red and red, color-wise.
In a darkened room, you may be able to see some color ("blood red") down as cold as maybe 900° F. Red starts to become orange at about 1600 or 1700° F. You need to be closer to the "top" of the red range, rather than the bottom if you are to either hard or anneal simple carbon steels. If you are going to try again, get a magnet. Slowly heat the part, checking to see if the magnet is attracted or not. At room temp and up to about a "medium" red, the magnet WILL be attracted to the part. As you continue heating, the magnet will, at some point, no longer be attracted to the part. This is the point where you would quench the part to harden it. In general, (others--- don't flame me for this) I would not forge the part very much below this temp either. I also would not forge this material much above a mid orange.
A caveat in all this is that different people see colors differently. That's why a magnet is important at least until you "calibrate" yourself.

In your last post, it was unclear what your goal was when you heated the part and put it into the sand. Were you trying to forge the part cold after you took it out of the sand? Were you trying to anneal (soften) the part by heating it and putting it into the sand?

There are lots of other pieces to the pie here. For instance, many old files were made of plain carbon steels, where the above process would work to some degree. But, if the file were made from a more modern alloy steel, attempting to anneal one in a bucket of ashes (okay), let alone sand (not so okay, in my book) probably won't work at all.

One hour at a forge with a somewhat seasoned blacksmith could cover more than you will get from hours of typing here.
But if you keep trying and keep asking questions based on your results, you will get there eventually this way.

You should take this link to my webpage on getting started in blacksmithing and follow its advice:

Pete Stanaitis
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Old 06-17-2011, 05:42:32 PM
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Default Re: Annealing a File

Thanks, Pete. I have some blacksmithing experience but not with files. Read that many Confederate knives were made from files.

Heated my Blackhawk file red (but which red) and let it cool in ashes. Then reheated it red (see above) and it broke into pieces on the first hammer blow.

My blacksmith friend Bob Woodard said to stay away from this. If I'm successful I can't make enough and if I'm not it is very frustrating. For right not I have more irons in the fire but appreciate your contact information. I usually don't know when to quit.
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