|
|
|
|
Basic Forging: File Knife
Start the fire using a mixture of tinder and vegetable coal, soaked
with kerosene or gas oil.
When the coal is properly lit, add a shovel-full of rock coal.
Once the coke is burning, place the file on its side between the coals
and start blowing air with a turbine (hand operated), this must be
done consistently and at a moderate speed.
After the file reaches the desired temperature, a light red or dark
orange color, place it on the anvil and forge the point. It has to
form an angle similar to that shown in picture 5. You have to hammer
all four sides of the file, this will help you both achieve an angle
like the one in the picture and make the file thinner as well.
With the point finished, it's time to start forging the edge of your
knife. In order to do this, you need to heat the steel again and start
hammering the lower half of the blade with moderate strength. This way
you'll start thinning and stretching down the steel. It's important to
do these on both sides of the file, otherwise you won't get a centered
edge.
Repeat this process through the whole length of the file. The knife
will start to take shape. As you can see from picture 8, as we stretch
the steel down to the point that we forged in the beginning it has an
upward curve that will later become the blades "clip".
When using this technique of "pulling the edge down", you must broaden
the part of the file that is going to become the knife's handle.
Unfortunately, I don't have pictures of that part of the process, but
I don't think it will entail any difficulties.
In the photograph you can see the finished product from the forging
process. The edge could be much thinner and even, but this is a very
basic tutorial and we'll have to make due with what we've accomplished
so far.
Part 2
Grinding.
For this part of the process I always turn to one of the belt grinders
in my workshop, but since I'm trying to do this in the most basic
possible way, I'm going to use common, easy to find, tools.
You'll need a large file (the bigger the better!), stones of at least
to different grains and sandpaper (which will be used later on), water
and a lot of patience.
Before you get started, you need to make sure that the blade is very
soft. After forging it, let it cool slowly in a sheltered place, the
best way to do it is to let it sit in the ashes of the forge. Heat
treatment experts, don't get your panties in a bunch, this is just a
tutorial for beginners. Give me a break!
Hold the blade in a vise. Start the grinding by marking the blade's
ricasso, which is the thickest part of the blade and will be used to
determine all other thicknesses.
As you can see from the picture, you have to hold the file at a
certain angle, 25º (more or less) is about right. This way, by the end
of this chapter, the edge area will be smooth and the body of the
knife will show a characteristic file pattern.
After just a few firm strokes the edge will start to show. Now is
the time to move on to the rest of the blade. In this picture you can
also see some depressions left on the blade by the hammer, don't worry
they'll disappear as you go through the rest of the process.
Using a stone, the coarsest one you can find, even out both sides of
the blade. Hold the blade in the vise and move the blade on it.
Remember to keep the 25º angle and to keep the stone wet. This
process, like the previews one, needs to continue over the whole blade
until if feels smooth to the touch.
Once you're happy with the results, move on to a medium grain stone, I
prefer natural stones. Do the same as in the previews step, hold the
stone in the vise and move the blade over it, like it's shown in the
picture.
You're almost there! After the blade has been ground with the medium
grain stone, heat treat it.
Part 3
If you look at the picture, you'll notice that some material needed to
be removed from the handle area to make it more comfortable, so I used
a hacksaw to make it more comfortable.
Once you achieve a tang shape you're happy with, you need to even it a
bit, so when the time comes to put the scales it will be easier to get
a good fit.
The filing technique is simple and easy. Just make sure that the
surface is as even as possible.
After filing both sides of the tang, you can drill the holes for the
pins. This is the difficult, or rather time consuming, part of the
process.
I used a manual drill that belonged to my great-grandfather (Pedro
Gugliotta), with a new bit since I knew there was some hard work
ahead. Even with the new drill bit, using kerosene to lubricate and
taking turns with a workshop assistant it took me over fifteen minutes
to drill a single hole. As you probably guessed, I used an electric
drill for the other hole.
There's another method, much simpler, which I didn't think about until
it was to late: Just use a center punch of the same size as the pin.
As they say, hindsight is 20/20...
In the picture you can see the tang, filed and drilled, ready for heat
treatment.
Part 4:
In the picture you can see the changes I made to the forge for heat
treatment. You just need to place two hearth bricks on their sides,
forming walls that will help contain the coal better than an open
forge.
Once the coal is properly lit, place the blade amongst them edge down.
The kind of heat treatment we are aiming for is differential, the kind
that will produce a hard edge and a soft back.
To achieve this, you have to keep moving the blade amongst the coal.
Once the hardening temperature is reached, around 800º, sink the blade
into burnt oil, grease or water with salt, I used burnt oil. How did I
know when the hardening temperature was reached? I just trust my
trained eye, but you should use a magnet. When the blade starts
turning orange, take it out of the fire and check it with a magnet,
when it doesn't stick it's ready. Try it, it works like a charm!
When sinking the blade into the quenching liquid (oil), do it point
first and without hesitations! Move it up and down, three times, more
or less, and let it cool until it reaches room temperature.
That's it, it's hardened! Look at the picture, you can see that the
part of the blade that received more hardening appears white, and the
rest of the knife is black. This is not a discoloration of the steel
or anything like that, it's just that when hardened, the steel's
structure becomes more "compact", if you will.
Part 5
The blade has been hardened, but the heat treatment isn't over. You
still need to temper it. This is done to take tensions off the blade
and make it less brittle. When I say that the blade is brittle, I
don't mean that it will break if we look at it wrong, but a good field
knife like this one needs to be able to stand any use and abuse.
Light the forge again, I used one with higher walls so I could load it
with a lot of coal,
Start a nice fire and, once all the coal is properly lit, place a
metal tube on the bed of coals.
Turn the fan off (or stop cranking it!). Then insert the blade, edge
up, and let it heat up.
But why? Do you remember that I said the we were going for a
differential heat treatment? With this process we are trying to
accentuate that hardness difference. Keep in mind that this is a field
knife that is certainly going to end up chopping wood.
The ideal color is a sort of blueish hue, don't let it go any further.
Keep an eye on the blade!
Once it's blue, take it out of the fire and let it rest on sand or
ashes, if you have non let it rest somewhere sheltered from the wind.
As soon as it is cold enough to touch, it will be ready for use.
  
    
|
|
