Butterfly knife
A balisong, also known as a butterfly knife, fan knife or Batangas knife, is a type of folding pocketknife that originated from the Philippines. Its distinct features are two handles counter-rotating around the tang such that, when closed, the blade is concealed within grooves in the handles. A latch sometimes holds the handles together, typically mounted on the one facing the cutting edge. An exceptionally large balisong is called a balisword.
The balisong was commonly used by Filipinos, especially those in the Tagalog region, as self-defense and a pocket utility knife. Hollow-grind balisongs were also used as straight razors before conventional razors were made available in the Philippines. In the hands of a trained user, the knife blade can be brought out to bear quickly using one hand. Manipulations, called "flipping", are performed for art or amusement. Blunt "trainer" versions of these knives are also available and can be used to practice tricks without the risk of injury.
The knife is now illegal or the length of the blade is restricted in some countries, often under the same laws and for the same reasons that switchblades or concealed weapons are restricted, additionally having restrictions in some countries due to the balisong being classified as a gravity knife. Within the Philippines, it is no longer as common in urban areas as in the past.
Name
Names for the knives in English include "fan knives" and "butterfly knives" from the motion, and "click clacks" from the sound they make when they are opened and closed.The name "balisong" is derived from barangay Balisong, part of the municipality of Taal, Batangas province, which along with the neighboring barangay Pandayan, were the original manufacturing centers of the knives in the Philippines. The two barangays were home to a blacksmith industry that also produced other bladed implements such as bolo knives. It is also claimed that the meaning of the term balisong is derived from the Tagalog words baling sungay as the hilt of the blade was traditionally made from carved carabao and deer horn, as well as bones. The traditional balisong is also known as veinte y nueve or "twenty-nine" in the Philippines because they are long when opened.
History
The origin of the knives is unclear. Oral histories claim that the knives were first created in the Philippines in 800 CE. However, there is no documentation or archaeological evidence to back this. Balisong's mass production in the Philippines can only be attested to the early 1900s. Another claim is that the balisong was originally an adaptation of a French measuring tool called the pied du roi, invented between the 1500s to the late 1760s. However, how it was introduced to the Philippines is unknown. There are theories that it may have been introduced by sailors in the Spanish Empire, which was then allied with France.Regardless of origin, the modern balisong was perfected in the Philippines, where it became much larger and was predominantly used as a weapon, not just a tool. The quick opening techniques were also developed in the Philippines. In contrast, the French pied du roi was primarily a folding ruler, with the knife only included in some specimens as a novelty. They were cumbersome to open and unlikely to be used for self-defense, especially since they also commonly included a metal tang at a right angle from the end of the handle to aid in measuring. There were also very similar designs to the balisong produced in England in the late 19th century, presumably also derived from the pied du roi. But like the latter, they were primarily utilitarian tools.
Construction
There are two main types of balisong construction: "sandwich construction" and "channel construction".Sandwich-constructed balisong knives are assembled in layers that are generally pinned or screwed together. They allow the pivot pins to be adjusted more tightly without binding. When the knife is closed, the blade rests between the layers.
For a channel-constructed balisong, the main part of each handle is formed from one piece of material. In this handle, a groove is created in which the blade rests when the knife is closed. This style is regarded as being stronger than sandwich construction.
A version known as faux-channel construction also exists, where the handles are sandwiched between channel spacers that mimic the feel of a channel handle while being customizable with different types of spacers. Another variation is speed-channel construction, where a hole is milled out on the outside groove of the handle to support flow while flipping.
Sometimes, the handles can be made smaller in width to support a scales/liners system. Scales are the main handle construction in either the sandwich construction or the channel construction. Liners are the outside cover to make the full-sized handle. These liners are commonly made from G10 fiberglass or carbon fiber.
Additionally, the two main construction types can be combined to form a "chanwich construction", a portmanteau of "channel" and "sandwich", which involves two halves of a channel handle screwed together. The chanwich construction can be divided into 2 types: standard chanwich and speed chanwich. Although rare, this construction generally keeps the best elements of both constructions and discards the worst, as it retains the better handle shape channel construction is known for, while still allowing adjustment of the tightness the handles are held together to some extent, as well as easier access to the inside of the handle for cleaning.
There are also three types of pivots systems that balisongs use: bearings, bushings, or washers-only.
Bearing-operated balisongs have small ball bearings housed in a circular concavity around the hole in the pivot. These bearings allow the handles of the balisong to rotate.
Bushing-operated balisongs have a small metal bushing slightly thicker than the tang in each pivot hole, with a usually bronze disc known as a washer on each side. These washers clamp down on the bushing, but not on the tang, when the pivot screw is tightened, allowing the handle to rotate around the tang.
There are also washer-only operated balisongs, which are usually much cheaper and lower quality than the other kinds, as they don't need bushings, but the handles will always bind to the tang when the screws are tightened enough, and the washers, tang and handles all wear themselves down much faster due to the increased friction.
Some of the blades of traditional butterfly knives in the Philippines were made from steel taken from railroad tracks, thus giving them a decent amount of durability and toughness, while others are made from recycled leaf springs of vehicles.
There are 2 types of pin systems: tang pins, small pins on the tang of the blade that space the handles, preventing them from hitting too hard, stopping blade wobble, and engaging the latch; and zen pins, which are two small pins embedded in the top of the handles of the balisong that make contact with the bottom of the blade. In certain knives the zen pins are hidden, embedded into the handle construction. While a balisong with zen pins is easier for the end user to perform maintenance on for the end user and significantly easier to design, they do not hold up as long as tang pins would in a properly made knife. The force of the harder blade contacting the soft zen pins will mean they need to be replaced far more often than tang pins, which should be mild steel, so the blade doesn't crack and can cushion against soft handle materials rather than crush each other.
Some modern balisongs also have a "pinless" system, in which they do not have any pins, and instead rely on the material of the handles to make contact with the blade, similar to how zen pins work. The longevity of the pinless is exceedingly short and not meant for long-term usage before the system itself fails and the knife breaks.
Parts
; Bite handle: The handle that closes on the sharp edge of the blade, and will cut the user if they are holding that handle when the knife closes. This handle usually carries the latch.; Choil: The unsharpened portion of the blade just above the kicker, which makes it easier to sharpen the blade.
; Jimping: Grooves at the near ends of the handles to support certain tricks and provide comfort while flipping.
; Kicker : Area on the blade that prevents the sharp edge from touching the inside of the handle and suffering damage. This is sometimes supplanted by an additional tang pin above the pivots.
; Latch: The standard locking system, which holds the knife closed. Magnets are occasionally used instead.
; Latch, Batangas: A latch that is attached to the bite handle.
; Latch, Manila: A latch that is attached to the safe handle.
; Latch, Spring: A latch that utilizes a spring to propel the latch open when the handles are squeezed.
; Latch gate : A block inside the channel of the handles, stopping the latch from impacting the blade.
; Pivot joint: A pin about which the Tang/Blade/Handle assemblies pivot.
; Safe handle: The handle that closes on the non-sharpened edge of the blade.
; Swedge: Unsharpened spine of the blade. Some balisongs are also sharpened here or on both sides with either a more traditional look or wavy edges similar to a Kris sword.
; Tang: The base of the blade where the handles are attached with pivot pins.
; Tang Pin: Pin meant to hold the blade away from the handle when closed to prevent dulling; and, in some cases, a second pin to keep the handles from excessively banging together while the butterfly knife is being manipulated.
; Zen Pins: Screws mounted inside the handles that collide with the kicker mounted on the tang to prevent the blade from moving around while in the open or closed position.
; Blade: The blade is a piece of steel that runs down the center of the knife, secured by both handles when closed. One edge of the blade is sharp and will cut the user if they are not careful, especially when flipping the knife. The other side is called the spine and can have what is known as a swedge. The swedge is a blunt bevel ground in for looks and won't cut the user. The spine commonly impacts the user's hand when flipping. Some knives will have a dual-edge blade, with both sides of the blade having a sharpened edge. Some models that uses the dual-edge blade include: Benchmade 49, Krake Raken Zenith, or the Kris Talisong
; Bushing: A small barrel of steel included in the blade so the handles can be tightened without back and forth movement. The bushing is a highly precise element of modern balisong knives and requires specialized tuning to function properly.