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 Tom Mills | Home > 
Forging a Knife Blade
A photo essay showing how I forge a knife blade from an old file.
Date(s): February 21, 2004. Album by Tom Mills. Photos by Tom Mills. 1 - 24 of 24 Total. 7171 Visits.
  Sign the Guestbook. Displaying 10 of 21 entries.
Thanks for the time you took to write this up! Great looking knives imo...
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Tom, Sat, 21 Apr 2012 11:59AM
enjoyed you knife making. Thought I was the only one who poor boyed That process.
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Harmey Randolph, Thu, 5 Jan 2012 12:33PM
I don't think that a person has to follow a link to another site. All of the information here makes perfect sense. A file is made from high carbon steel and it holds a good edge. This is what you want a good knife to do also. If you want to make a pry bar then you had better search out another material. I use my knives for cutting and over the years have made many knives from discarded files with very good results.
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Don, Tue, 20 Sep 2011 2:17PM
just an old guy that likes tinkering with stuff. nice to learn something new
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roger gilbreth, Mon, 11 Jul 2011 5:56PM
I was reading your article on the war sword and how it was made with old leaf spring metal, to create swords/knives/daggers, and found it very interesting. I work for SDTruckSprings.com and being
that we work with these, things all day. Its nice to see them put use rather just sit there at a scrap yard or in the wear house, and with customers always buying new leaf springs --- obviously they have
old leaf springs; so we decided to write about a trend we've spotted on your site and show our customers what some are doing with their old leaf spring metal. So we wrote an article about it which you
can find here. Hope you enjoy!
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Mike DelVecchio | http://www.sdtrucksprings.com, Wed, 9 Feb 2011 9:38AM
I have checked a few sites around and so far yours was the easiest and most affordable way yet. I am currently making a few myself, and i am very eager to try your tempering procedure first hand. Thanks for the tips!
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Eric, Thu, 18 Nov 2010 2:44PM
i am 16 and have made a few but your pictures with info has helped me out a ton!
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Eddy , Tue, 9 Feb 2010 8:36PM
looksee
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orville, Mon, 28 Dec 2009 8:09AM
I would like to know how to forge a knife blade and how to make a forge
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Donald Shannon | msn, Mon, 21 Sep 2009 7:56AM
how to shape knives from old files or leaf springs
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Arnoldo cisneros, Wed, 8 Jul 2009 12:49PM
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All you need to make a great knife from an old file are a few tools:  An old file, a forge, something for an anvil, some coal or wood charcoal, and a new file (or belt sander, grinder, etc) to shape the blade and put cutting edge bevels into it.  Here's a simple forge that's designed for long blades.  They're easy to make and only cost a few bucks.  Pay no attention to the blow dryer bellows!  The anvil cost me $30. It's a piece of junk from a discount tool store, but it works for me.  If you want, you can use the head of an old sledge hammer for an anvil.  I did!
"Your set-up looks better t..."
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My new blade forge.  My first forge, made of an old tire rim, was insufficient to properly heat blades over 6" or so.  I made this out of an old wash-tub.  There's a trough in the center with the air inflow pipe at the bottom.  I cemented the pipe in place with a combo chicken wire and cement like plaster called "hydrocal".  The stuff deteriorates with heat, and eventually you have to replace/repair it, but not for a long time.  The file cost less than a buck at a garage sale.

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After selecting an old file (I like Nicolson files), I usually  hot-cut it to its general length.  Hot cutting is merely using a chisel to cut the file while at a nice cherry red heat.  Another easier way is to clamp a file in a strong vice, and hit the sucker with a hammer.  A file is so hard, that it will snap like a piece of glass.  Any stress put into the metal from this maneuver will be released once you heat the metal in the forge.  I usually opt for the hammer/vice method!
"As you can see, I'm using ..."
"hey Tom I really love the ..."
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After cutting the file to the lenth of the desired knife, it's a good idea to hammer in the cuting bevels.  By hammering them in, you'll save lots of time at the grinder, or belt sander.  Hammering the bevels will take a number of heats (don't hit the steel with a hammer unless it is cherry red! Return to the heat, as necessary).  As you hammer the bottom edge, you'll see the blade curve upward. Hammer on the top edge to minimize the upward bend, or don't worry about it.  You can grind it even later.

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After your bevels are hammered in, you should anneal the steel so that it is soft and easier to shape at the grinder and/or belt sander.  All annealing involves is bringing the steel up to critical heat (cherry red - where it no longer attracts a magnet), and letting it cool as slowly as possible.  The best way to do this is to get the steel to critical heat, and then burry it in the wood ashes or dry vermiculite.  It may take several hours to cool this way.  With my gas forge, I usually cheat and just shut off the forge, close the door and let the steel sit inside until cool.  It takes about 2 hours to cool this way (not enough for a full annealing, but good enough for me). The longer it takes to cool, the easier it will be to shape the knife.

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This is the same piece of steel from photo #4.  Having hammered in the bevels on the anvil, it takes just a few minutes to make it look like a knife.  I'm using a 2"x42" belt & disk sander (Sears, about $99 on sale).  I started with a hand held 3"x21" belt sander turned upside down and clamped to a workmate bench.  I still use that one for finish up work!

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Basic shape and cutting edge bevels are nearing completion.  Need some more work on the belt sander, but this is almost ready for heat treat and tempering.

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Going to put a birch bark handle on this blade.  If you're interested, take a look at the birch bark handle photo album.

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Alrighty...the blades are ready to be hardened and tempered.  First, I'll normalize the steel by heating to critical heat (non-magnetic) and let cool at air temperature.  I'll do this 2 or 3 times (usually only 2 times, cause I'm always ina rush).  Normalizing releases stresses in the steel that we put there by beating the crap out of it with a hammer.  Doing this before quenching keeps the blade from warping, or worse yet, cracking.  Ever since I learned to do this, I haven't cracked a blade!

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Critical heat is where the steel becomes non-magnetic.

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Real knife makers will probably laugh at my normalizing strategy!  I put them in the clamps so that they can be positioned in such a way as to release their heat evenly.  I read that when normalizing, you should orient the blade north/south.  I don't know what the reason for that is (when I first read that, I thought it was a joke...but apparently not), but I do it anyway.
"North to south positionnal..."
"what keke said could have ..."
"actually the guy i read it..."
"Magnetic flux is the reaso..."
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After nomalizing 2 times, I'm anxious to quench (i.e., harden the steel).  I've set up a bucket of pre-heated veggie oil (no particular temp, I just warmed it up a bit).  I've got the bucket of oil close by so I can move quick from the forge to the oil.

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Stand back Jack!  This is my favorite part.  I'm holding the blade in tongs and trying to take a photo at the same time.  I got lucky with this shot, cause I was moving fast.  The still photo makes it seem that I'm slowly lowering the blade, but that's NOT so.  I'm moving quick!  You can see the oil starting to boil as the blade enters the oil.

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The oil boils and then flashes into flame.  Smells like the drive-in at that fine Scottish restaurant, McDonalds!  I've plunged the blade straight down and am holding it as still as I can.  The flame only lasts for af ew seconds. I've read different things about quenching - move the blade, don't move the blade, quench only the cutting edge, etc.  This way has worked for me so far, so I'm just sticking with what has worked before.  WIll try other methods soon.

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Love that forge scale!  Reminds me of the Lord of the Rings and the complexion of the Uruk-hai (those evil creatures spawned from the flames of Isengard).  If I could keep all of the forge scale, I would.  I like it!

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Too bad all of this forge scale will be gone!

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Cleaning up the cutting edge so that we can see the color changes during tempering.  I use about a 120 grit for this purpose (note, this pic was borrowed from the initial grinding stage. That's why no forge scale).
"i think that if you quench..."
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Real knife makers will cringe when they see my tempering technique!  I use a propane torch on low, and simply heat the spine of the knife up as evenly as possible.  In theory, I look for the golden color to hit the cutting edge, and I quench quicly in water.  I intentionally messed this one up, by only heating the back part of the blade.  When the color hit the edge, I quenched it to stop the tempering.  I'll then return to "paint" some heat/color on the remainng part of the blade.  If it starts to turn a dark brown and then blue color, you've gone too far!

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Her's a better shot of the partially tempered blade.  I'll return to the heat source to temper the front of the blade to the same color.  Some folks advocate tempering in an oven at about 400 degrees.  I tried that once and over did the blade real quick.  This way, I feel I have more control.  I'm sure I'm doing it wrong, but the blades come out great and I don't care!

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Here's a knife made from one of the three blades above.  The handle is bloodwood/brass.  The sheath decorated & dyed leather.

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Same knife as previous photo - again, made from one of the three file blades above.

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This blade was also one of those in the photo above.  I'm in the process of putting a lacewood handle on the last of the 3 blades.  Should be finished in a day or so!
"dont you find using old fi..."
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Here is a work in progress.  This was the dagger blade above.  I decided to try making a Scottish dagger (called a Sgian Dubh).  The handle is Osage Orange - it will turn dark orange with time.  I kind of messed up the blade, having sharpened it on both sides.  Sgian Dubhs only have one side sharpened, and the other only appears so (or so I've read).  This one would be illegal to carry around.  Next time I'll make it the right way.

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Here's the finished birch bark handle knife (left).  The knife on the right was the longer blade above.  I'd snapped off the tang on that one by mistake (I'm too embarrassed to say how).  A friend of mine saved me by welding it back on and fixing up the blade for me.  I made the sheaths out of tooling leather.

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