Pivot System

The pivot system of a balisong determins how the handles rotate around 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. At this point, the sexbolt, washers, handles and screw function as a single, solid unit, meaning they move together without any friction between them. The blade acts as a second independent component, meaning it is allowed to freely swing around the handles. The only friction in this systems is between the washers and the blade.

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. After screwing the pivot screws in, check the tolerances and adjust the screws accordingly.

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.

Assembling Washer Only

When you are disassembling an already assembled washer only balisong, make sure to note the orientation of each washer and reassemble everything exactly as it was. There is an exception: Sometimes phosphor bronze washers come with a smooth/rounded and a rough/blocky side. The smooth side should always face the blade to ensure a smooth swing and prevent binding. Some manifacturers overlook this detail and install the washers incorrectly. In that case you should flip the washer so the smooth side faces the blade.

Bushing

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

The bushing pivot 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 blade's 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. At this point, the sexbolt, washers, bushing, handles and screw function as a single, solid unit, meaning they move together without any friction between them. The blade acts as a second independent component, meaning it is allowed to freely swing around the handles. The only friction in this systems is between the washers and the blade and between the outer diameter of the bushing and the blade as the bushing "scrapes" against the insides of the bushing holes of the blade.

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-4.8mm (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 6.350mm for their Replicant
Nabalis uses 6.985mm for their Vulp
Baliplus uses 7.052mm for their Titanium Barebones clone.
Squid Industries uses 6.350mm for their Nautilus
Baliplus uses 6.299mm for their Serif clone.
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 Forwards And Backwards

Length

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

Assembling Bushings

When you are disassembling an already assembled bushing balisong, make sure to note the orientation of each bushing and washer. Reassemble everything exactly as it was. That means inserting each bushing into the same side of the blade using the same washer on the same side as before. That is because once a washer has been pressed against a bushing, the bushing will press a small groove into the washer, forming a bond, which means that the washer should only ever be re-used with that specific bushing with the same washer side facing the same bushing side. This is sometimes called "marrying".

Please also read #Assembling_Washer_Only as everything that has been written down there, also applies to bushing balisongs.

Bushing Tuning

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 the balisong will behave as if it was running 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 the optimal length 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 the #Lapping_Methods chapter.

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. This can be done by bending the sandpaper in the other direction and/or by taping it down to a straight and sturdy surface.

Sharpening Stone

Resin bonded diamond sharpening stones can be used as a premium and longer lasting lapping surface compared to #Sand Paper. They allow for more security against uneven bushings and more consistent lapping since they get worn out a lot slower.

Stay away from cheap sharpening stones like those shown in this video: https://www.youtube.com/watch?v=V5shv-7m5Ic, as they tend to develop a recess in the center over time which will make your bushings uneven. They also come with a range of other problems covered in the video. 

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

Regardless of whether you are using sandpaper or sharpening stones, you should also invest in a strop. Stropping helps reduce any bur that may form on the edges of the bushing during lapping and removes residue stuck to the surface. This results in a smoother, more consistent 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 will probably also want to apply some stropping compound on your strop before using it.

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

Avoid chromium oxide oxide compounds, as they are not suitable for high-hardness stainless steels.

For more information on strops, watch this video: https://www.youtube.com/watch?v=pMnS1jU4904. Even though it focuses on knife sharpening, much of it also applies to bushings.

Lapping Methods

There are different lapping methods depending on the tools you have.

Always lap only one side of the bushing. This keeps the bushing as flat as possible and makes it easier to fix the bushing if it becomes uneven.

Uneven bushings are extremely common, as factories usually dont sell perfectly flat bushings and all lapping methods will introduce some degree of unevenness. There are two proper ways to fix uneven bushings.

1) Buy slightly oversized bushings. This way, you will spend as little time as possible on the lapping surface, reducing the chances of introducing uneveness. However, this method comes with its own set of problems as this method is very unreliable and some bushing sellers, like TheTrueLink have been known to send out bushings that are shorter than advertised.

2) If your bushings are a lot taller than your target height, for example 0.100mm taller, then you must manually even out the bushing as described in Uneven Bushings.

By Hand

If you have no lapping tools, you will have to lap the bushing by hand. Start by placing your bushing flat-side-down on your lapping surface and lap the bushing in a circular or figure-eight motion while applying even and constant pressure across the whole bushing. After a few motions, usually between 3 and 10 (in this example we will use 5), but always keep the number of motions the same, rotate the bushing 90 degrees. Repeat this process three more times. In total you should have performed 4 rotations (ending back at your original position) and 20 circles or figure-eights (5 per rotation). This completes one pass.

After you have completed one pass, you should #Strop the bushing. Use the exact same technique as described above, but with stropping, you do not have to follow the steps as precisely because stropping removes little to no material. After that, you should check if your bushing is uneven and make it even again as described here: Uneven Bushings.

Check the tolerances as described in this chapter: Checking tolerances and repeat as needed.

KnifeDogs Pivot Lap

The KnifeDogs pivot lap includes one puck, multiple adapters and multiple plungers. Every plunger fits exactly one adapter perfectly.

To begin, you first need to figure out which adapter fits your bushing. Start by try placing your bushing insde one of the the adapters. If the adapter hole is too small, try one one with a larger hole. If the bushing is loose inisde the adapter, pick an adapter with a smaller hole. If your bushing fits perfectly inside the adapter with little to no wiggle, you have the correct adapter. Next, you need to find the correct plunger. Use the same process as before, but instead but instead of putting the bushing into the adapter, you need to try putting the plunger into the adapter.

After you have found the correct adapter and plunger, place the puck on your lapping surface with the logo/text "KNIFEDOGS PIVOT LAP" facing toward you. It is recommended to use a high grit sanding surface, around 1200 grit, as the pivot lap removes material quickly. Insert the adapter into the puck and place your bushing inside the adapter with the side that you want to sand, facing downward. Next, insert the plunger into the adapter so it sits on top of the bushing.

After that, press down on the plunger and on the puck and move the entire assembly in circles or figure eights across your lapping surface. On a 1200 grit resin bonded diamond stone, 10 circles will remove about 0.003mm of material, but your results may vary. When you have just purchased the pivot lap, the adapter will have a small lip that will hold the bushing inside the adapter. This lip will gradually wear down with use, so be careful not to drop or lose the bushing when lifting up the pivot lap. After you have done a couple of circles or figure-eights, strop the bushing.

Do not strop your bushing with the pivot lap as this will damage the strop. Always strop the bushing by hand with the stropping technique described near the end in the #By Hand chapter.

After stropping the bushing, check the tolerances and repeat as needed.

Nabalis Bushing Buddy

Place a white (soft) or black (hard) rubber ball inside the groove in the middle of the Bushing Buddy body and slide the sandpaper through the hat of the Bushing Buddy, so that some sticks out on both sides. At this point you can lube the grooves which are on the side of the bushing buddy for a smoother experience, but this is not necessary. Next, put your Bushing on top of the rubber ball, with the side you want to sand facing up. After that, put the hat on top of the body, making sure that the notches on the sides are aligned with the grooves. Then rotate the hat 10 times while applying light downward pressure from the top.

After that, take the hat off and check the tolerances and repeat as needed.

After you have completed one pass, you should #Strop the bushing. The instructions for stropping are covered at the of the By Hand chapter.

Troubleshooting Bushings

Here are some common issues, alsong with tips, tricks and solutions to help diagnoes and fix problems when your balisong doesn't behave as exprected.

Adjustable Handle Gap

If your handle gap shrinks when you press the handles together, for some balisongs, this is normal. However, if the change is excessive, it's likely that the #Inner Diameter of your bushing is too large.

Handles Move Forwards And Backwards

If your handles shift shift or "click" forward and backward (towards or away from the blade when your balisong is open), the #Outer Diameter of your bushing is likely too small.

Unexpected Binding

Binding that happens even though the balisong seems properly assembled can have several causes.

Wrong Sized Washer

Check the height of the washer that you currently have installed in your balisong. Some balisongs, like the Replicant require thinner washers than others.

Uneven Bushings

This is the most common cause for binding. A small amount of unevenness is usually acceptable, but the tighter your tune, the less tolerance there is before your balisong starts to bind. For example a difference of 0.030mm might not cause issues on a loose tune, but even a difference of 0.010mm can cause binding.

If you have a micromenter, measure the edges of the bushing's flat surface. If the measurements differ, the bushing is uneven. If you do not have a micrometer, there unfortunately is no precise way to confirm unevenness.

Stainless steel washers are especially problematic with uneven bushings because the hard washer will get forced into the blade, causing the edge of the washer to grind into the blade. This issue is far less severe with phosphor bronze washers, as the softer material will "glide" against the blade even if the bushing is not perfectly flat.

To solve this problem, you will have to sand the part of the bushing that is longer by hand. Begin by taking measurements at multiple points around the flat face of the bushing and note each reading. The greater the difference between the smallest and biggest measurement, the more uneven your bushing is. Identify the area with the highest measurement, this is the part that needs to be sanded. Place the bushing on your lapping surface and apply only preassure on the side that had the highest measurement while grinding the bushing against the lapping surface. This will remove material from the entire side you are sanding, but significantly more from the are where you apply pressure, so if you tune was already very tight, this procedure you will probably undersize the bushing.

After you have made sure that your bushing is not uneven anymore, #Strop it.

Uneven Washers

Washers usually do not become uneven on their own, especially if they are stainless steel washers, but just like with uneven bushings, uneven washers can also cause binding. As with an #Uneven_Bushing, you can try sanding the side of the washer that is thicker. However, removing too much material can lead to other issues, such as the chanwich seam on Tsunamis opening up. In most cases, you're better off simply replacing the washer.

Uneven Blade

To check if your blade is uneven, measure the area around the pivot hole, where the washer would normally contact the blade. If the thickness varies, the blade is uneven. Fixing this is extremely difficult. While sanding the thicker area, as described in #Uneven Bushings might seem like a solution, it is not practical as this method is not precise enough for a blade. Proper correction would require a surface grinder, which most people don't have access to. Your best option is to run the balisong with a looser tune. Some people try using stainless steel washers, hoping the harder material will gradually wear down the uneven blade, but this can cause other issues and is generally not recommended unless your bushings are perfectly even and you're okay with experimenting.

Used-Up Washer

This mostly affects phosphor bronze or brass washers, as stainless steel washers are too hard to get deformed significantly.

Phosphor bronze or brass Washers will wear down with time and they will develop a groove in the center due to the pressure from the bushing. When you reassemble your balisong, it's pretty much impossible to align the bushing perfectly with that groove again. As a result, one side of the washer will press harder against the blade than the other, which can lead to binding.

To fix this issue, you can lightly sand both sides of the washer with a low grit #Lapping_Surface, usually only around 10 circles or figure-eights per side. This removes the roughest imperfections and flattens out the washer. After that, repeat the same process with a high grit #Lapping_Surface. This helps smoothen the washer and improves swing. After that, you can Strop the surface of the washer. Do about 100 circles or figure-eights per side. Stropping removes almost no, if any material, but helps to refine the surface further. After stropping, your washers should have a reflective finish, though not quite necessarily a full mirror polish.

You can also try applying pressure to the pivot area as if you were trying to snap the handles off the blade. For a visual demonstration, watch this video: https://youtu.be/tcGMmcxFaQM?feature=shared&t=1316 and jump to the 21:56 mark.

At this point, reassemble your balisong and check the tune by #Feel. If the binding is still present, but reduced, you can repeat the process. Just be careful to not remove too much material, or you may end up with new problems which are described in #Uneven_Washers.

Checking tolerances

Checking the tolerances is very important to ensure that you are tuning your balisong correctly.

Micrometer

A micrometer is not necessary, but highly recommended, as it makes it much easier to identify what kind of bushing you are working with (undersized/oversized/uneven).

Usage

Before measuring any surface, make sure that the surface you want to measure is free from any dust or oil. The same goes for the spindle and anvil of the micrometer. After that, you need to make sure your micrometer is zeroed correctly. Start by fully closing the measuring gap of your micrometer. Then press the "zero" or "ABS" button. Once it's zeroed, open the micrometer, insert your bushing and close the measuring gap of the micrometer.

Important: Never force the micrometer shut. Always use the ratcheting wheel (the one that makes the clicking sound) to apply even and consistent pressure. Forcing it can damage the tool and will give false readings.

Feel

To check your tolerances by feel, assemble and lube your balisong and hold the balisong as if you are about do do a double rollout. From that position, grip the handle that is closer to your palm and tilt the knive vertically to the right if you are right-handed, left if you are left-handed. Now shake the balisong forwards and backwards quickly. If you can feel the balisong rattling/moving, you have play. If you can hear a "clicking/tapping" sound, then you have tap. If you cant feel either, then check the swing. If you have constant and smooth swing all the way through, then you have a good tune. If the handle gets stuck or feels "sticky/gummy" at any part during the swing, then you have bind. If you have bind, check

Conversion

It is possible to convert different types of bushing systems.

Floating Washers To 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.