The Railroad Hori Hori – Redux

Railroad spike becomes a hori hori with riveted veg-tanned leather (finished February 2022)
The original hori hori knives I made from RR spikes (August 2016)

It’s useful on occasion to revisit one’s earlier work. The two photos above contrast the results of my ‘smithing over a six year period. The first picture is my latest hori hori creation, forged from an old railroad spike, hardened, sharpened and finished with walnut handle slabs. The second photo is a set of hori hori that I made for the Nikka Yuko Japanese Gardens in Lethbridge, AB. It was a great learning experience for me, and looking at the older photo now I can see both how my design has changed over time, and how my ‘smithing has changed.

A “before and after” of the forging process, 2022.

The big, iron block is a 250 lb. Japanese pattern anvil I purchased from my friend and mentor, Dave J Friesen of Crossed Heart Forge. Using that, and an eight pound hammer, has really increased my efficiency. There’s quite a bit of material to move in the spike. It’s a mid carbon steel so it’s not as tough as spring steel, but it starts out at 5/8″ thick, and I forge that down to 5/32″ at the hilt of the blade with a slight thickness taper to the point. Two holes are drilled in the handle for steel pins to secure the handle slabs.

The finished hori hori and the two hammers I use to forge with. 8 and 4 lbs. 2022.

The serrations have seen some modification over the years, too. For the Nikka Yuko hori hori, I used a half round file but it seemed to me the teeth were too shallow and didn’t saw very well. I then switched to a small chainsaw file for the knives made from coil spring, and that worked ok but I think the teeth were a bit small. The serrations, according to my research and personal experience, are designed to saw through woody materials such as thick roots and small branches. The latest iteration uses a large chainsaw file for deeper teeth which should make for quicker cutting and sharpening (less teeth to sharpen).

The scooped blade is formed by forging into a shallow piece of pipe, cut in half. The first railroad hori hori knives had a very slight scoop by forging with a round peen along the length of the blade. I leave the scale from forging on the blade as it inhibits rust, and it wears off over time anyhow because of digging in the soil.

The blade and handle are hardened in room temperature vegetable oil. This gives a hardness a bit below an axe, and allows for quick field dressing with a bastard file and chainsaw file if needed. There’s no need to make the edge razor sharp as the first stab into soil acts like sandpaper. The balance between hardness and toughness is important; it’s hard enough so that sharpening isn’t required too frequently, while remaining tough so the knife doesn’t snap when prying a plant out of the ground.

The handle is a simple affair: two slabs of walnut, or whatever scrap hardwood I have lying about, pinned with two steel rivets. A woodworking tool that I love to use ever since Dave J showed me is the Japanese saw file. It works quickly and leaves a finish that needs only light sanding to smooth out. The bevels on the handle are formed with that saw file. A coating of linseed oil seals and protects the wood.

Our tuxedo cat comes by for inspection.

After discussing the sheath design with my wife and striker, Lorinda, I decided to try a cross carry instead of the traditional wooden sheath or vertical sheath that’s common with factory models. The cross carry keeps the handle out of the way when bending over or kneeling, which is a very common stance in the garden. The vertical carry can make drawing the knife a bit awkward, and these knives are easily misplaced if not kept near at hand. This is an experiment at this point, but I really like how it came together.

The leather sheath is fitted to the scooped blade to ensure a snug fit while preventing the edges from slicing up the inside of the sheath. Copper rivets secure the belt loop and the sheath itself. I thought about using copper rivets on the handle, too, but decided on steel for the extra strength they provide.

I look now at the requirements for a good hori hori knife and I realize I picked a really hard tool to start with. Back in 2016 I had only been a hobby smith for about a year. The hori hori has a difficult blade shape, two sharpened edges, and needs just the right balance of hardness and toughness. I ruined a good number of promising knives when they warped after quenching and tried bending them back. Pretty sure the neighbours heard my dismay when the blade went <snap>! Other times I would spend an hour or more heating up a warped blade, forging it straight, normalizing it and quenching once again… only to have it warp again. Thankfully, I can say that no one who has purchased one my knives have had them break or bend, which is a common complaint about the factory models.

I’m looking at trying my hand at other hand tools, now that I have a good number of years of experience under my belt. Wood carving knives, draw knives and broad axes are next. Hopefully I can make at least one of each this year and see where that takes me.

One Blade Becomes Two

Sister Blades

Working on some new tool designs, I took an old lawn mower blade and recycled it to use as stock for a kusakezuri (Japanese hand hoe) and a hori hori. In my continuing study of Japanese agricultural tools made with reclaimed steel, I’ve created these as prototypes. The fact that the two blades are sisters really speaks to me, and I plan to let whoever becomes the owner of these tools know it.

The kusakezuri blade, ferrule and handle unassembled. The blade needs hardening at this point.

The hori hori blade with tape measure to capture the scale.

Heat Treatment Process

The hand hoe is ready for heat treatment. The process involves annealing (which I did already), then normalizing the blade for two or three cycles depending on if the blade warps as it cools. Finally, the blade will be hardened by quenching. For this particular steel from the reclaimed lawn mower blade, I took a piece of it and tested it. It hardened very well at a cherry red heat quenched in room temperature water. For longer pieces like a blade, however, quenching it in a medium like that could cause it to warp excessively or even crack from the stress of cooling so quickly.

I next tried hardening the test piece in warm vegetable oil (came out soft), and then cold vegetable oil. The second result had ok hardness (a file barely scratched it). I decided to quench the hori hori blade in the cold vegetable oil. This is the result:

A slight curve can be seen along the blade’s edge. This needs to be corrected.

The blade warped slightly, curving upwards, and the edges were a little soft for my liking, with the file biting a bit. The ideal is a file skating on the surface of the hardened steel. I’m going to harden the hori hori again, but this time using yaki-ire to harden the edges. I will use the same process for the hand hoe as well.

Yaki-ire is a style of edge hardening that is accomplished by applying a clay mask to all surfaces of the blade except for the edge. When the 1-2 mm clay layer is dry, the blade is heated to the correct temperature and then quenched in water. Water quenches faster than oil, so I believe this will give the hardness that I want while maintaining some toughness in the rest of the blade.

Blade Anatomy

A slight concave is forged into the back of the hoe blade to ease in sharpening.

Tang detail: note the sharp shoulder where the tang meets the ferrule.

The back side of a single bevel blade is called ura in Japanese, and in the picture above I forged a slight concave on the ura to make sharpening easier. This is a traditional method for forging single bevel blades. The blade will fit into a slot cut into a hardwood handle. An iron ferrule is used to support the tang and blade; for the support to work correctly the ferrule must fit snugly with both the tang and the wood. It takes a bit of work to ensure all the pieces fit properly.

Next update will show the completed pieces.

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