Turning Pins and Bushings: How and Why You Should Do It
Turning Pins and Bushings: How and Why You Should Do It
Reading time: 7 min
If tracked machines are part of your heavy equipment fleet, then you’re probably familiar with pins and bushings. These small but crucial components are key to the functioning of tracked heavy equipment like dozers, excavators and tracked skid loaders.
Pins and bushings work together to support the weight of the machine and transmit force from the engine to the tracks.
Maintaining your machine’s pins and bushings is one of the most important maintenance requirements for tracked heavy equipment. One important task in properly maintaining your tracked machine is turning its pins and bushings.
What Does it Mean to Turn Pins and Bushings?
Turning Pins and Bushings involves removing pins and bushings from your machine’s tracks, rotating the pins and bushings end-for-end, then reinstalling them in the track. This is done so the pins and bushings wear down more evenly over time.
Tracked heavy equipment moves on tracks that are made up of a series of interconnected metal links. Like a bicycle chain, this chain of metal links is rotated by the machine’s sprocket – a giant cogwheel that supplies power from the engine.
Bushings are hollow metal cylinders that connect two links in the track together. Pins slide through the bushings and rotate inside of them as the track rotates around the sprocket. Over time, pins and bushings can wear down, causing slack in your machine’s track and leading to inefficient performance.
Bushings are especially susceptible to wear in two places – on the exterior of the bushing, due to frequent interaction with the sprocket, and on the interior of the bushing, due to the friction of the pin rotating inside the bushing.
Crucially, pins and bushings do not wear down evenly. They tend to wear down on the reverse-drive side, as this is the side of the bushing that interfaces more aggressively with the sprocket.
When you “turn” the pins and bushings in your tracked machine, you remove the pins and bushings from the track and flip them, end-for-end, so the fresh side will receive wear from the sprocket.
Advantages of Turning Pins and Bushings
The main advantage of turning pins and bushings is the resulting boost in longevity to your machine’s track. Turning pins and bushings can extend the life of a track so that it does not need to be replaced or serviced until the machine’s rollers require maintenance.
Wet Turns vs Dry Turns: What’s the Difference?
On modern machines, turns of the pins and bushings can either be wet or dry.
Wet turns apply to lubricated tracks, or SALT chains. SALT stands for sealed and lubricated track. On SALT chains, the pins contain an oil reservoir and a self-sealing plug in one end of the pin. This plug is used to fill the pin with oil, which gets dispersed inside the bushing during operation.
As part of a wet turn, the self-lubricating pins are refilled with oil before they’re reinstalled in the bushings.
During dry turns, also called grease turns, pins and bushings are simply reassembled with grease. Dry turns are the only option when turning pins and bushings on tracks that aren’t self-lubricating.
Sometimes, when the self-lubricating components of a SALT chain have deteriorated and the pins can no longer be refilled with oil, a technician may choose to do a dry turn on a self-lubricating track.
Turning Pins and Bushings vs Replacing Them
While turning pins and bushings used to be part of standard maintenance for tracked machines, the practice isn’t as common as it once was. There are a few reasons for this.
For starters, many tracked machines today use SALT chains. In a SALT chain, the pins have self-sealing holes drilled on one end of the pin that receive oil. The oil flows from the self-sealing valve to a reservoir inside the pin that lubricates the inside of the bushing over time. SALT chains greatly reduce wear on the pin and to the interior of the bushing, thereby making internal wear less of a concern.
In addition, modern pins and bushings are much stronger than they were in the past. Improved forging techniques have resulted in bushings that wear down more slowly over time, even on the exterior of the bushing where it interacts with the sprocket.
Finally, it’s more expensive to turn pins and bushings than it was in the past. Turning pins and bushings requires specialized knowledge and equipment, which have become costly commodities relative to replacement parts.
Given these factors, many heavy equipment managers simply opt to replace the pins and bushings and/or track, rather than spending a similar amount to rotate the pins and bushings.
How to Turn Pins and Bushings
The exact process for turning your machine’s pins and bushings will depend on a number of factors, like your machine’s size, age, track type and make/model. Here is a general overview of the process:
- Use a hydraulic press or a steel drift with a sledgehammer to dislodge the pins and bushings from the links. Be careful not to damage nearby components during this process.
- Clean the link bores, pins and bushings with a suitable solvent to remove debris.
- If you’re doing a “wet turn,” then you’ll need to refill the pins with oil using a vacuum pulled through the pin’s oil reservoir. For a dry, or “grease,” turn, grease the components with a heavy coat.
- Reinstall the pins and bushings on the track, flipping them 180°, or end-for-end. Make sure that the pins are straight and fully seated in the bushings
With larger machines, it isn’t always possible to dislodge the pins from the track without the use of specialized equipment. The pins are frequently stuck in place and can only be dislodged with a hydraulic pin press.
Depending on the type of pin, you may also need a special vacuum to add oil to the pin’s reservoir.
If you don’t have these tools, or you’re not sure how to turn the pins and bushings on your own, then it’s best to seek the help of a qualified service technician.
Signs of Worn Pins and Bushings
The most obvious sign the pins and bushings are worn is slack in your machine’s track. As the pins and bushings wear down, clearance develops between the pins and the interior of the bushings. Excess space between these components eventually causes the track to sag.
While excessive slack is the most common indicator the pins and bushings are wearing down, there are some other symptoms to look out for:
- Abnormal Noises: As the pins and bushings wear down, the track can get loose and begin to rattle, causing unusual noises that can be heard from inside the operator’s cab.
- Uneven Wear: Worn pins and bushings can cause uneven wear on the track components, including the shoes and sprockets. This can lead to premature wear and tear on these parts.
- Reduced Traction: Worn pins and bushings can cause the track shoes to lose grip, reducing the machine’s traction and making it more difficult to operate on uneven terrain.
- Reduced Efficiency: As the track becomes loose, it can cause the machine to consume more fuel and require more maintenance to keep it operating efficiently.
When to Replace Pins and Bushings
Pins and Bushings should be replaced when visible slack has developed in the machine’s track. While there are many factors to consider, like the size and type of machine, replacing your machine’s pins and bushings may be a better solution than simply turning them.
If you notice your machine’s track is visibly sagging during operation, then it’s probably time to replace the pins and bushings. Other indicators include abnormal noises coming from the chain, uneven wear on track components and reduced traction.
While turning the pins and bushings can also remove slack from a sagging chain, there are limits to how many times you can turn them. And under some circumstances, it isn’t possible.
This is frequently the case with self-lubricating pins/bushings as the oil reservoirs in the pins break easily and can no longer be refilled past a certain point. When this happens, replacing the pins and bushings is a better option than trying to repair the pins. Aftermarket pins and bushings are available for many machine makes and models. Therefore, replacing them can end up being less costly than turning them.
Get Help From The EquipmentShare Shop
If you decide it’d be best to replace the pins and bushings in your machine, the EquipmentShare Shop is a great place to start. Check out our collection of pins and bushings to get the right ones for your needs. Still can’t find the part you’re looking for? Reach out to one of our parts experts for personalized assistance.