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.
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:
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.
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.
In this video I show the steps I take to finish the forged and tempered hori hori. It’s broken down into four essential steps:
Grind bevels to final shape – using files and/or a bench grinder with various grits of belts, I take the edges down on both sides of the blade to their final shape. The finished angle of the bevel is about 30 degrees, to ensure a robust edge since the knife is used primarily for digging
File serrations into one edge – using a round file, I file in serrations into one edge. This helps with sawing through fibrous roots and woody stems.
Wrap the handle – The handle is wrapped with brightly coloured paracord so that if the knife happens to be left in the garden, it’s easy to spot.
Sharpen the edges – Finally, I use a sharpening stone to get the edges to their final sharpness. I don’t go as far as making the edges razor sharp because they would lose that edge pretty quickly digging in soil anyways. The knife is still sharp enough to cut paper, and it chops through wood readily.
Lorinda demonstrates how the kama is an ideal tool for selective harvesting and cutting of green plants and herbs. Here she is specifically harvesting leaves and flower buds from a comfrey patch.
The kama can be used for many other applications such as harvesting garden greens, squash, and cutting grasses and weeds around trees and other sensitive perennials. To find out more about the kama and how it’s made, visit this page.
Lorinda and I love using this tool around the garden for pretty much any cutting job for herbaceous plants.
It’s harvesting time once again, and here we’re showing you how we get our garlic out of the ground. The broadfork is an indispensable tool for harvesting because it 1) digs up the plant we want and 2) loosens and aerates the soil at the same time and thus prepping the bed for spring all in one go.
Lorinda and the hens are the stars of this video. No music this time as I wanted to highlight how quiet it is working with hand tools as opposed to machinery.
This spring my wife and I recorded us preparing a garden bed for planting using three tools that I make: the broadfork, the russian hoe and the hori hori. Each tool has specific functions that complement one another, culminating in a garden bed that’s weed free and cultivated without putting through the equivalent of a soil blender (powered roto-tiller). We had a bit of fun with this as well!
Fernie Forge is a business based near Fernie, British Columbia and operated by Sandra and Dave Barrett, both master blacksmiths from England. My wife and I had the good fortune of meeting them both during our honeymoon last fall. When we got to talking shop, Sandra expressed interest in featuring some of my work at their gallery, The Eye of the Needle Studio, located in the heart of Fernie’s downtown. It’s a beautiful location that features work from blacksmiths and other artists from around the world. I was honoured that she considered my work good enough to be included in their gallery.
If you are ever in the Fernie area, I highly recommend stopping by their gallery.