Pivot System

The pivot system of a balisong determins how the handles rotate aroudn the blade. There are currently four types of pivot systems.

Washer

The washer pivot system, often referred to as "washer only", uses only washers between the blade and handles. While other systems may include washers as part of a more complex setup (like bushings), a washer only system relies solely on the washers.

In this system, the blade is sandwiched between two washers, which are usually made out of phospor bronze. This washer-blade-washer assembly is then clamped between the two handles. A sexbolt goes through the entire stack: handle-washer-blade-washer-handle, to keep it from fallig apart. A pivot screw is screwed in from the other side to keep the sexbolt from falling out.

Tuning Washers

Tuning a washer balisong is done by adjusting the tightness of the pivot screws. The torque applied to the screws determines how freely the handles rotate. If the screws are too tight, the balisong will bind. If the screws are too loose, the balisong will feel losse and might even tap.

Because a proper tune relies on not fully tightening the screws, you will not get full thread friction retention. This means that the screws are more likely to loosen over time as compared to a bushing system. To prevent this, some form of threadlocker is typically used.

Bushing

A bushing is a small cylinder, usually made out of heat-treated stainless steel.

The bushing system is sometimes also called "traditional bushing system" or "normal bushing system" because there is another pivot system that uses bushings, the floating washer system. However, since the traditional bushing system is by far the most common pivot system, people will assume you're reffering to traditional bushings, when you meantion "bushing".

In a traditional bushing system, the bushing goes inside the blades pivot hole and gets sandwiched by two washers on each side. This washer-bushing(which is inside the blade)-washer assembly is then clamped between the two handles. A sexbolt passes through the entire stack: handle-washer-bushing(which is inside the blade)-washer-handle, to keep it from fallig apart. A pivot screw is screwed in from the other side to keep the sexbolt from falling out.

Sizes

Bushings have 3 measurements: outer diameter, inner diameter, and height.

Inner Diameter

Often abbreviated to ID.
The ID of most bushings will usually be the same, around 4.7mm-4.9mm (0.188in)

Outer Diameter

Often abbreviated to OD.
Unfortunately there is no standard for bushing sizes. Some balisongs may use the same bushing size, but this is not guaranteed. For example:
Bladerunners Systems uses 6.35mm-6.36mm for their Replicant
Nabalis uses 6.985mm for their Vulp
Baliplus uses 7.052mm for their Titanium Barebones clone.
Squid Industries uses 6.326 for their Nautilus
To see a list of which balisongs use which type of bushing, check out the balisong list.

While some of those differences may looks small (for example: 6.985 vs 7.052), they can still dictate whether a bushing might or might not fit inside the bushing hole of a blade. You can use a small bushing for a larger bushing hole (for example 6.985 inside a blade that needs 7.052) but that will introduce problems. Please read Tune#Handles_move_up_and_down

Length

The last axis of the bushing is the length. It is the only flat part of the bushing.

Tuning Bushing

One of the main advantages of a traditional bushing system is that, when set up correctly, allows for a perfect tune: no tap, no play and completely free-swinging handles with no bind.

Tuning a traditional bushing system involves adjusting the length of the bushings, typically by sanding, untill it is only slightly longer than the thickness of the blade. If the bushing is too long, the blade will have too much side-to-side movement between the handles and in extreme cases, the blade will hit the handles and it will tap. If the bushing is too short, you will have bind because at that point, the bushing becomes useless and its like you are on a washer-only system.

The optimal length for the bushing varies between balisong to balisong, blade to blade and even pivot hole to pivot hole (so never mix your bushings and always keep track of which bushing you have tuned for what pivot of what blade), but it is usually at least 0.025mm longer than the blade. A good starting point is 0.045mm and then go from there. If your bushing is 0.025mm (0.001in) shorter than your blade, you probably have an undersized bushing and your balisong will most likely bind. You must also be careful to not sand your bushing at an angle because this will make your balisong bind, but only in specific handle positions. Some community members tend to call uneven bushings "lopsided". There are measures and tools to counteract an uneven bushing. These measures and tools will get discussed in later chapters.

Lapping Surface

You will need some surface on which you can lap your bushings.

Sand Paper

Most people use sandpaper. While sandpaper usually works just fine, it usually comes warped/curled, so you run the risk of making your bushing uneven because the side of the bushing which is closer tho the warped part of the sandpaper, will automatically have more pressure applied to it, making your bushing uneven. So if you want to use sandpaper, make sure to properly straighten it out before you start lapping your bushings.

Sharpening Stone

Sharpening stones are the more premium and longer lasting lapping surface. They allow for more security against uneven bushings and more consistent lapping since they get worn out a lot slower. Here is a decent sharpening stone:

Amazon DE: https://www.amazon.de/dp/B07GRWN1PV?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1&th=1

Amazon US: https://www.amazon.com/SHARPAL-Diamond-Whetstone-Storage-Sharpening/dp/B07GRWN1PV

Grit

While you can successfully lap a bushing with only one grit size, at least two grit sizes are recommended: a coarse and a fine grit. Something like 325 and 1200 grit work just fine. You should use the low grit when you are far off your target bushing length, and the high grit when you are close, so that you do not accidentally overshoot your target and end up with an undersized bushing.

Strop

Independant of whether you want to use sandpaper or sharpening stones, you should also buy a strop. A strop will help you minimize the bur that might form on the edge of your bushing that comes from lapping and removing residue that might be stuck to the bushing, allowing for a smoother, more even bushing surface.

Amazon DE: https://www.amazon.de/-/en/SHARPAL-204N-Leather-Polishing-Sharpening/dp/B09KV5D79X

Amazon US: https://www.amazon.com/SHARPAL-204N-Polishing-Sharpening-Woodcarving/dp/B07WC1M411?th=1

You probably also want some form of stropping compound.

Stroppystuff is considered a well regarded brand for stropping compound, but the price reflects that. https://stroppystuff.com/products/6-micron-mono-diamond-suspension-high-concentration-30ml

Do not use any chromium oxide stropping compound, as it is not a fitting stropping compound for high hardness, stainless steel.

If you want more information on strops, watch this video: https://www.youtube.com/watch?v=pMnS1jU4904. It is about knife sharpening, but a lot of things said in that video also apply to bushings.

Micrometer

A micrometer is not necessary, but highly recommended, since it helps a lot with identifying with what type of bushings you are dealing with (undersized/oversized/uneven).

Lapping Tool

There have been tools invented specifically for lapping bushings.

Conversion

It is possible to convert different types of bushing systems.

Floating Washers -> Traditional

A floating bushing system can be converted to a traditional bushing system. Currently the instructions are missing on how to do this, but a community member called Taktyc has created a video in which he announced that he will make a tutorial about this.