Intro: Leaf Spring to Gurkha Khukri
The kukri is a large knife, originating in Nepal, the national knife. The kukri is as iconic in that region, as the Bowie knife to western culture. It's a multipurpose knife, with a history or brutal efficiency. It was carried by every Gurkha soldier as a last resort weapon. They were kept razor sharp, and sliced through enemies with ease. They developed a legend around themselves. It was symbolic of the soldiers. There are kukris in museums dated at over 500 years old. The knife may be even older, with connections to the classic Greek sword Kopis. It's a core part of the nations history, even well known to most of the world.
The blade has a curve on the front as well as extra mass for a heavier weight. Another interesting point on the construction on a typical kukri is the notches on the blade, similar to a choil. However they say it stops the blood from dripping onto ones hand. This protects once grip, and increases longevity of the handle. The knife also has two other small knives associated. They are either in the sheath or in a separate case. They are called Karda and Chakmak. The Karda is a small utility blade, and thr Chakmak is a blade for sharpening.
I wanted to recreate the kukri in a way that pleased me. I was looking for a more hefty construction, not accurate to history. I also have a different curve and head size. I probably won't be making the small knives either. Regardless, I have always been intrigued by this Nepalese knife, and wanted one of my own. Let's get started, shall we?
Step 1: Type of Steel
I have really enjoyed using steel leaf springs for knives and swords. If I'm not mistaken it is typically 5160 steel. It's a fairly easily workable metal, with good strength.
For this machete I started with about an 18 inch section. I cut off the holes, and started forging. I then marked out the dimension of the piece on the table, and drew a finished goal to reference.
Step 2: Forging
I didn't get very many pictures of this part, but anyways.
I started by hammering the front down to a point. I simply lined up the tip toward the side of the anvil and started smashing away.
The kukri has a much heavy portion toward the front of the blade, so I started hammering the sections prior to that.
With each few hits, I had to flatten the piece again, since the edges would thicken up with each blow. It made for a very long process since I needed to make it about half as wide as it was initially.
Hammer after hammer.
The blade wasn't pointing down far enough, so I had to grind it down to shape. Halfway through, when I did that, I also ground the profile to a closer shape, before returning to forging.
I continued stretching out the thin portion of the blade and the handle. With it all sized down I hammered out the belly of the handle and rounded the back of the handle.
To divide the spot between the blade and the handle I forged a choil.
Step 3: Drilling
Drilling holes can be very challenging. Different types of steel harden in different conditions.
Some steels will harden some just by cooling off in the air. Others may harden from a splash of water.
Another issue is work hardening. By forging the steel, it may build up a hardness even though it wasn't quenched.
When I drilled these holes, I was having trouble. I had to anneal the steel. Annealing is heating up the blade to critical temperature and letting it cool very slowly to relief hardness and stress from the steel.
I used three cycles of heat and cool. I let it cool in a fireproof insulating environment.
I drilled the holes first with a smaller drill bit. Before I annealed it I broke a drill bit in the handle. I resorted to drilling different holes and having some holes run though the blade for glue.
Step 4: Grinding
I have never ground a bevel that had an inward curve. You can't use the flat surface of the grinder like typically (At least as easy). I opted to to use the larger wheel on the bottom to do all the grinding.
I started with a steeper angle until I reached about the middle of the blade thickness minus the middle 1/16 in. Following that i gradually decreased the angle, by cutting farther up the blade.
I started by grinding the whole edge, top to bottom. As I got closer to finish I would grind smaller portions, focusing on evening everything out.
Near the base of the grind it was thicker, caused by the curve of the wheel. Ideally, its an issue, but has no major issues.
I cleaned up the grind with a flap wheel on the angle grinder. It makes quick work, and looks good. I also used it to fix the cutting edge/bevels.
I went to the scotch brite belt and cleaned the whole thing.
On to heat treat (HT)
Step 5: HT
Heat treating is synonymous with quenching and hardening.
It is aligning/locking the carbon atoms in the steel by cooling it at the proper speed. Some steels use oil, others water, air, or soapy combinations.
I generally use oil, as it's a safe guess that people typically have luck with. I have used it on leaf spring, and it seems to do well. I need to do a stress test on a blade at some point, I'll make a video.
I quenched in a bucket of oil, and used the scotch brite belt to clean it up. Then I applied some beeswax after slight heat.
Step 6: Cut and Glue
First you gotta select your wood. I used some section of wood I had in my box.
I marked the approximate size with a sharpie. I cut it out with the table saw. I cut the piece in half to make the scales. I then lined up the scales with the front of the handle section. I marked the spot in the hole for the pin with a punch.
I drilled the hole on the spot. The pictures show the process pretty well. Next I put it the pin through the blade and the scale with the hole. With them held together, I drilled through the other hole of the metal, to drill into to scale.
For the other scale's holes:
I marked the hole with a punch the same way as with the first one. I drilled out the hole. I then used one pin to line up the scales with the blade, and marked the next spot, through the other sides holes. I drilled it out.
I checked the fit and moved on
Step 7: Preglue Shaping
The hardest part to shape on a knife handle is the front edge toward the blade. Because of this, I find it essential to shape that first.
I just used 80 grit paper to put a radius on the front. Reference pictures for size.
With the front shaped, its time to glue.
Step 8: Gluing
I glue everything together with a two part epoxy from harbor freight. I used the saw dust from the last step to color the glue. I had beeswax on the handle so I sanded this off. I slathered all surfaces, including the pins. I pressed them together using a vise. A few clamps can be used as well.
Now for my minor innovation
I always have the pins be a bit wider then the scales. These get in the way when I try to clamp it all in the vise. I got around this by drilling holes in a couple boards, and letting them grip the kukri. This allows the pins to go through and apply pressure instead on the scales. This ensures a solid gluing. I let the glue cure for a few hours.
Step 9: Handle Shaping
Step 10: Finished
There you have it. Please use the comments, let'em fly