This punch is specifically designed to create nakago-ana (tang opening) in iron or copper tsuba, saving time with a cold chisel and files. The concept is to forge something shaped similar to a tang but with an exaggerated taper for strength.
The tool could be hardened but will likely lose its heat treatment during the drifting stage so best to keep the neck sturdy and short enough to hold up either way.
Working at very high heat will help prevent splitting when punching wrought iron. The tsuba in this video is medium carbon steel.
As time allows, the plan is to forge a bottom die (rather than use the hardy hole) to reduce the amount of distortion at the edges of the nakago-ana and speed up the drifting process, reducing the required number of heats to drift.
Hand carving a classical tanto style mounting from reclaimed and local natural materials using traditional Japanese woodworking tools.
A note about the wooden koiguchi: I don’t recommend this method with any wood other than Oceanspray ironwood due to its peculiar strength in cross section…wood (or better, horn) grain should run vertically across the opening to add strength to the koiguchi in the correct areas.
The abrasive plant material used for fine sanding/polishing is dried tokusa (polishing grass), known as horsetail in english…the plant cells contain silica and it can be used dried as is or glued to wooden blocks with sokui.
Hand filing a classical tanto style blade forged from half of a reclaimed horse carriage leaf spring. (4x) Arashiage is the rough shaping stage that comes after hizukuri (fire shaping) and before yaki-ire (hardening). Serious students of the forge can watch the full process version here: https://youtu.be/m659YKUiu80
Charcoal forging a traditional tanto style blade from half of a reclaimed horse carriage leaf spring at 4x speed (total actual forging time including heating was about 2 hours). Serious students of the forge can watch the full process version here: https://youtu.be/y7fROs7i8-U
The two distinct stages are sunobe and hizukuri…sunobe establishes the geometry and proportions, and hizukuri is putting in the bevels and creating the final shape. The final dimensions take a little extra care as this blade is being forged very closely to a traditional kata.
The finished forging has a subtle recurve and a slightly dropping spine compared to the kata as the process of yaki-ire will cause the spine to curve upwards.
Shear steel is a very old and somewhat rare form of steel produced by increasing the carbon content of wrought iron using heat and charcoal to create a reduction atmosphere and then forge welding and folding layers together to homogenize the billet. The finished blade has distinct visible layers telling the story of its history.
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A workshop visit from the The Samurai Carpenter
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