An Inside Look at Handle Geometry

A rare opportunity to compare the inside and outside geometry of a finished handle core. Historically an old tsuka would be split open for repair or adjustment or even re-purposing for a new blade, however a newly crafted tsuka is always glued together before the outside is shaped.

In this unusual case the core was opened and adjusted at a late stage in shaping, providing an example to study and observe. The proportions in the example below are generally based on study of a range of antique sword tsuka, with the main difference being the kataki (hardwood) style lacking samegawa and silk cord wrapping.

An Inside Look at Classical Tanto Handle Geometry
First recall how the tang sits slightly off center in the block, the omote side is carved slightly deeper than the ura along the edge side to support the steel and keep stress off of the glue joint.
An Inside Look at Classical Tanto Handle Geometry
The edge of the tang is cradled by the omote (left) but fades away on the ura (right).
An Inside Look at Classical Tanto Handle Geometry
The handle flows along with the spine of the tang.
An Inside Look at Classical Tanto Handle Geometry
The spine of the tang is supported half by the omote (shown top) and half by the ura (shown bottom).
An Inside Look at Classical Tanto Handle Geometry
The mekugi peg comes through from the omote (top) towards the ura (bottom).
An Inside Look at Classical Tanto Handle Geometry
The off center split is visible, omote sitting on the bottom, ura on the top.
An Inside Look at Classical Tanto Handle Geometry
A view of the joint fitment, omote on the bottom, ura on the top.
An Inside Look at Classical Tanto Handle Geometry
Ideally the grain lines up and runs across the handle slightly diagonally.
An Inside Look at Classical Tanto Handle Geometry
The tang sitting in the omote, ferrule removed, because this is a kataki (hardwood style) handle the ferrule sits lower, ending up flush with the surface.
An Inside Look at Classical Tanto Handle Geometry
The tang sitting in the ura, note the spine of the tang is half supported on each side.
An Inside Look at Classical Tanto Handle Geometry
Tang in the omote, note the mekugi-ana in the tsuka is smaller than the mekugi-ana in the tang.
An Inside Look at Classical Tanto Handle Geometry
Tang in the ura, note how the mekugi pulls the tang back pressing against the mekugi-ana to create tension on the tang between the ana and the machi and compression on the tsuka between the ana and the seppa/tsuba.
An Inside Look at Classical Tanto Handle Geometry
If the ferrule were a proper fuchi there would be a small space between the tsuka and the tsuba/guard.
An Inside Look at Classical Tanto Handle Geometry
The edge of the tang sits fully in the omote and is flush with the surface.

An Inside Look at Classical Tanto Handle Geometry


More about the interior of a traditionally crafted tsuka and saya:

View the archives for tsuka geometry or all classical tanto geometry.

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