The Habaki - Parts of a Japanese Katana
The habaki is a piece of metal encircling the base of the blade of a Japanese sword. It has the double purpose of locking the tsuba (guard) in place, and to maintain the weapon in its saya (scabbard) so the katana will not easily slide out. The first step in drawing a katana is by grasping the saya and applying pressure on the tsuba with your thumb to free the habaki from the saya called koiguchi no kirikata, at which point the blade can been drawn very quickly. This action could be considered an act of aggression by a samurai as it is putting your sword in a state of readiness much like drawing the hammer back on a revolver in the old west. The habaki will have normal wear as well as cause wear on the saya due to the wedging action which is why most are very simple in design. However, some of the elite katana makers treat the habaki like every other blade furnishing and form the habaki as a piece of art.
The importance of the habaki is seen in drawing the katana from the scabbard. It is drawn by grasping the saya near the top and pressing the guard with the thumb to emerge the blade just enough to unwedge the habaki from inside the scabbard in a process called koiguchi no kirikata cutting the koiguchi". The blade, being freed, can be drawn out very quickly. This is known as koiguchi o kiru, nukitsuke , or tanka o kiru "clearing the tanka". This is obviously an extremely aggressive gesture, since a fatal cut can be given in a fraction of a second thereafter. It is similar in connotation and effect as drawing back the hammer of a handgun, chambering a round on a pump-action shotgun, or pulling back and releasing the charging handle on other firearms.
The habaki will cause normal wear and tear inside the scabbard, and either a shim or a total replacement of the scabbard may be needed to remedy the issue as it will become too loose over time. Removing the habaki and oiling it after cutting or once every few months is recommended.
The habaki, or blade collar, sometimes been called the 'heart' of a Japanese sword and plays two important roles.
The first role is to simply mate with the koiguchi of the saya (scabbard) to ensure the best possible fit and keep the sword securely in its sheathe when not in use. When perfectly matched to the koiguchi, a Katana will be able to be turned upside down without falling out, yet able to be released by a small amount of pressure from the thumb on the hand guard.
The second role is perhaps the most misunderstood. For the habaki acts as a shock absorber, distributing impacts to the blade into the habaki before it travels into the handle, thus a well made and well fitted blade collar contributes to the overall structural integrity of a Katana.
A good habaki should have straight edges, sharp tendons, and fit the blade properly without shaking, so that it can protect the sword. Note: The shape of the gilt is a plug-like object (a structure that gradually narrows from back to front). The surface of the gilt is not completely flat, but has a certain curvature. This is also to ensure the ability of the saya carp mouth Better contact.