Excavator Bucket Repair Practical Guide: Complete Process of Pin Wear, Bushing Replacement and Welding Repair

Excavator buckets operate under high-intensity, high-wear conditions for extended periods, making pin wear, bushing loosening, and bucket tooth breakage the most common problems encountered on construction sites. Many owners face a dilemma: scrapping the machine outright is too costly, while simple repairs raise concerns about its lifespan. In reality, depending on the extent of damage and the usage scenario, most bucket problems have corresponding repair solutions—the key is determining when and how to repair them to truly extend their service life.

Based on real-world repair cases, this article covers the entire process from refurbishing worn pin bushings, key points of welding repair operations, disassembling and replacing damaged bucket teeth, to remanufacturing the bucket from raw materials. It helps you understand the repair strategies and limitations for different damage scenarios. Whether you're a novice in equipment maintenance or an owner hesitant about bucket repair solutions, this article will provide you with practical guidance.

At what point should the pins and bushings be repaired due to wear?

Wear assessment is not just about the size of the gap.

Many people assume that bucket wobbling means the bushing needs replacing, but the reality is more complex. A clearance exceeding the standard value (usually 0.5-1mm) between the pin and bushing will affect operational accuracy; this is a basic criterion. However, it's more important to pay attention to whether the wear is uniform and whether it's accompanied by deformation or cracks. If it's just surface wear, repair is worthwhile; if there's uneven wear or material fatigue, simple replacement may only address the symptoms, not the root cause.

There's an easily overlooked detail: when checking clearance, you can't just measure from one location. The pin experiences uneven stress during operation, and wear often concentrates on one side. You need to rotate the pin and measure the clearance at different angles to determine whether it's normal wear or abnormal uneven wear. If you find that the wear on one side is significantly greater than on the other, the problem may not just be with the bushing itself, but could also involve the bucket mounting angle or the excavator boom connection.

How to repair worn excavator bucket pins

There are two common approaches to pin repair; the choice depends on the degree of wear and your budget:

Welding repair is suitable for pins with wear ranging from 2-5mm. Restoring the original dimensions by welding a weld overlay followed by machining is the most common method used in repair shops. It's important to note that the weld overlay material must match the hardness of the original pin; otherwise, new uneven wear may occur. Many repairmen, to save time, directly use ordinary welding rods for welding, only to find the pin worn down again in less than a month – this is not uncommon. The professional approach is to use wear-resistant or alloy welding rods, and after welding, a tempering treatment should be performed to reduce the internal stress of the weld layer.

Coating repair restores dimensions using electroplating or thermal spraying techniques, suitable for connections requiring high precision, but it is relatively expensive and may not be feasible for small repair shops. The advantage of this method is a more uniform surface hardness and better wear resistance after repair. However, if your equipment is not used in particularly harsh environments, welding repair is sufficient.

One point easily overlooked in practice is that the pin must be checked for bending or deformation before repair. Some pins may appear to be only worn, but they may have already bent slightly under long-term off-center loading. If they are directly welded on without first straightening them, even if the dimensions are restored, the bushing will still wear faster after assembly, and the pin will have to be repaired again after a few months.

How to Replace Excavator Bucket Bushings – More Than Just Simple Removal and Installation

The most problematic part is when removing the old bushing.

The bushing and bucket lugs are usually an interference fit, and direct hammering can easily cause the lugs to deform or crack. I have seen more than once that repairmen, in order to save time, directly smash the bushing with a sledgehammer, resulting in cracks in the lugs. What should have been a simple bushing replacement ended up becoming a major project of welding the lugs.

The proven method is as follows: Locally heat the outer ring of the bushing (not the lugs) with an oxyacetylene flame, utilizing the principle of thermal expansion and contraction to reduce the interference fit. Temperature control is crucial during heating; generally, heating until the bushing surface is slightly red-hot is sufficient. Overheating will affect the material properties of the lugs themselves. Then, use a specialized pulling tool or hydraulic ejection device to slowly push the bushing out. If a specialized tool is unavailable, a simple pulling device can be made using a screw and a pad; the key is to apply force evenly and avoid impact.

Severely worn bushings may have become stuck to the lugs. In this case, it is necessary to first use an angle grinder to create axial grooves to weaken the bushing's strength. The groove depth should be controlled to about two-thirds of the bushing wall thickness, without cutting into the inner wall of the lugs. After grooving, the bushing will naturally shrink under stress, making it easier to remove after reheating.

Why does the bucket pin bushing still wobble after replacement?

Abnormal clearances still exist after new bushings are installed, a common problem encountered by many. Common causes include: mismatch between the inner diameter of the bushing and the outer diameter of the pin – only the bucket model was provided during procurement, without actually measuring the pin dimensions, resulting in bushings that do not match the specifications; the ear plate holes have enlarged due to long-term wear, requiring boring repair or welding before reprocessing; insufficient bushing press-fit depth, failing to fully fit the inner wall of the ear plate, leaving room for axial movement.

This is why experienced mechanics measure the actual dimensions of the ear plate bore and pin shaft before assembly, rather than purchasing them directly from "standard parts." Excavators of different brands and with different service lives, even those of the same model, may have different actual dimensions. Only by measuring and then customizing or selecting bushings with appropriate interference fit can the final assembly accuracy truly meet the standards.

When providing bucket parts to customers, Yuezheng Casting suggests that users provide actual measured dimensions or send in used parts for comparison. Although this adds an extra step, it effectively avoids rework due to size mismatches. For users who value equipment reliability and maintenance efficiency, this detail can often save a lot of time and money.

Boundaries and precautions for bucket welding repair

Under what circumstances is welding repair feasible?

Wear through the bottom plate, cracks in the side plates, and breakage of the bucket teeth can all theoretically be repaired by welding, but not all cases are worth repairing. The judgment criteria mainly consider two points: first, the area of ​​damage; if the wear through area of ​​the bottom plate exceeds 30%, even welding will hardly restore its original strength, and it's better to replace it directly; second, the location of the crack; if the crack appears in a high-stress area (such as the connection between the bucket teeth and the bottom plate), even if welded, it is prone to cracking again in the same location.

Here's a practical way to judge: if the bucket has been repaired more than twice, and the interval between each repair is getting shorter and shorter, it means that the overall structural fatigue is already quite serious, and at this point, continuing to repair it is not cost-effective.

Precautions for bucket welding repair

Welding repair is not simply a matter of filling the crack. Cracks usually extend inward, and if only the surface is welded, the internal cracks will continue to propagate under stress. The correct approach is to first use an angle grinder to round off both ends of the crack to prevent stress concentration, then use magnetic particle testing or penetrant testing to confirm the actual length of the crack, and finally perform full penetration welding by creating a V-groove along the crack.

The selection of welding materials is also important. Bucket bottom plates are generally made of wear-resistant steel plates. When welding, matching low-hydrogen welding rods must be used, with preheating before welding and slow cooling afterward. Otherwise, the weld is prone to hardening, making it more fragile. I've seen people use ordinary structural steel welding rods to repair buckets; the weld looks full afterward, but it breaks down after only half a day on the construction site. The root cause is the incompatibility of materials.

Another point that is often overlooked is that welding repairs can cause deformation. Especially when repairing a worn-through bottom plate, large-area welding can cause the bottom of the bucket to arch upwards, affecting its ground contact performance during digging. Experienced welders will use methods such as segmented welding and skip welding to control deformation, or apply anti-deformation pre-treatment with clamps before welding.

For construction teams that frequently need to weld and repair buckets, choosing reliable cast parts can significantly reduce maintenance frequency. Yuezheng Casting uses high-manganese steel and alloy steel to produce wear parts such as bucket lugs and tooth holders. These parts have superior wear resistance and impact resistance compared to ordinary castings, enabling them to maintain a longer service life under high-intensity operating environments and reducing downtime losses caused by frequent maintenance.

Bucket teeth disassembly method - seems simple but often causes problems

What to do if the bucket teeth are stuck and can't be removed?

The bucket teeth and tooth holders are connected by pins, and in theory, disassembly is simple: knock out the pins, and the bucket teeth can be removed. However, in practice, many bucket teeth cannot be knocked off due to hardened soil, rusted or deformed pins. Forced disassembly can easily damage the tooth holders, and replacing the tooth holders is much more expensive than replacing the bucket teeth.

A more reliable method is to first clean the dirt from the mating surfaces of the bucket teeth and tooth base with a wire brush, then spray with rust remover and soak for 10-15 minutes. If the pin still cannot be knocked out, you can use an electric welding machine to spot weld the head of the pin, using the instantaneous thermal expansion and contraction to break the rust layer. At this point, it will be much easier to knock it out. Note that the spot welding time should not be too long, otherwise the tooth base material around the pin will anneal and soften.

If the bucket teeth are worn and deformed, and stuck on the tooth holder, you can use an oxyacetylene flame to locally heat the root of the bucket teeth (not the tooth holder) to expand the teeth, then slowly pry them out with a crowbar. Never use an oxyacetylene flame to cut the bucket teeth directly, as the flame can easily damage the surface of the tooth holder.

Details that are easily overlooked when installing new bucket teeth

Many people simply hammer in the pins when installing bucket teeth, but the pins loosen and fall out soon after, causing the teeth to fall off as well. The correct procedure is: first, check if the pin hole in the tooth holder is deformed or worn and enlarged; if the hole diameter is out of tolerance, it must be repaired first; during assembly, apply a layer of grease to the pin surface to reduce damage to the pin and tooth holder during driving; after the pin is driven in, check if it is fully in place. The pin head should be flush with or slightly recessed into the tooth holder surface; if it protrudes, it means it was not driven in properly and can easily be knocked out during operation.

Some construction teams spot weld the ends of the pins to prevent them from falling off. This can be used in emergency situations, but it's not recommended for long-term use because disassembly after spot welding is troublesome, and repeated heating can affect the properties of the gear seat material. A more reasonable approach is to use locking pins or cotter pins, which prevent falling off and facilitate future replacements.

Under what circumstances is it necessary to remanufacture buckets from raw materials?

Several typical situations where replacement is worse than repair

When the bucket exhibits the following conditions, further repair is not worthwhile: the overall structure is severely deformed, and the angle between the bottom plate and the side plate changes by more than 5 degrees, which will directly affect digging efficiency and the stress on the excavator boom; multiple cracks appear and are interconnected, forming a network of cracks, indicating that the material has fatigued and failed; the ear plate holes are severely worn, and even if repaired by welding, it is difficult to guarantee coaxiality, which will accelerate the abnormal wear of the pins and bushings.

Another situation is that the bucket size or structure is not suitable for the current working conditions. For example, a standard bucket originally used for digging soil may not be suitable for digging rock, as the bucket wall thickness and material strength are insufficient. In this case, the cost of modification and reinforcement may be higher than that of customizing a new bucket.

What parameters should be considered when customizing a bucket?

If you decide to remanufacture the bucket, it's not as simple as just providing the excavator model. You need to specify: the main working conditions (earthwork, rock excavation, or mixed conditions), which determines the bottom plate material and thickness; the bucket capacity requirement—too large will affect digging force, and too small will reduce efficiency; the type and number of bucket teeth, as different geological conditions require different tooth models; and the connection dimensions, including the ear plate spacing, pin hole diameter, and distance from the hole center to the bucket bottom—these must be precisely matched to the excavator boom.

One point that many people easily overlook is the position of the bucket's center of gravity. A center of gravity that is too far forward increases the load on the boom, while a center of gravity that is too far back affects digging force. Professional foundries will calculate the optimal center of gravity position based on the excavator model and bucket capacity, ensuring balance during the design phase.

Yuezheng Casting provides detailed parameter confirmation sheets for its customized bucket services, including working condition analysis, material selection recommendations, and structural optimization solutions. For customers unsure of specific parameters, they also offer physical measurement services for existing buckets to ensure the new bucket fully meets actual needs in terms of size and performance. This customization service is particularly effective for older equipment or non-standard models, solving the problem of not being able to find suitable spare parts on the market.

Should the bucket be repaired or replaced? How should the cost be calculated?

It's not just about looking at the numbers on the quote.

Many people, when comparing repair and replacement costs, only look at the immediate cost, but this approach is incomplete. Factors such as how long the repaired device will last, whether it will affect operational efficiency, and whether subsequent maintenance costs will increase must all be considered.

For a practical example: the cost of welding and repairing the bucket of a medium-sized excavator is approximately 6-8 months after repair, and because the bottom plate is thinner, efficiency will decrease by 10%-15% when digging hard soil. While customizing a new bucket requires a higher initial investment, it can be used for 2-3 years without compromising operational efficiency. Considering the entire lifespan, the unit cost of using a custom-made bucket is actually lower.

Another easily overlooked cost is downtime. Repairs typically take 3-5 days, and during peak construction seasons, the losses from these few days of downtime can exceed the repair costs. Replacing the bucket with a new one, if parts are prepared in advance, can be completed in half a day; this time difference is invaluable during tight deadlines.

Under what circumstances is repair more cost-effective?

If the bucket is only partially damaged, such as a broken single bucket tooth seat or a small area of ​​the bottom plate worn through (no more than 10%), while the overall structure is intact, then repair is the wiser choice. Another situation is when the bucket is a custom-made non-standard part that cannot be bought on the market, and the lead time for custom-made new buckets is 1-2 months. In this case, even if the repair only lasts for a month or two, it is still necessary to use it in the meantime.

For equipment used infrequently, such as seasonal construction equipment used only for a few months a year, repair is more reasonable than replacement. Even if performance declines, the impact is minimal under low-intensity use, and there is no need to invest a large sum of money in replacing it with a new one.

Frequently Asked Questions (FAQ)

How often should bucket pins and bushings be inspected?

It is recommended to check the clearance every 500 working hours. If the working environment is dusty or the load is heavy, the inspection interval should be shortened to about 300 hours. During the inspection, pay attention to whether there are any abnormal noises or whether the bucket shakes more, as these are signs of accelerated wear.

What tools do I need to replace the bushing myself?

Basic tools include vernier calipers (for measuring dimensions), an oxyacetylene flame or heating rod (for heating the bushing), a puller or hydraulic jack (for removing and installing the bushing), and an angle grinder (for removing adhesions). If you do not have professional tools, it is recommended to have the work done by an experienced repair shop to avoid damaging the ear plate.

What inspections are needed after welding repair of the bucket?

After welding is completed, a visual inspection should be performed to check for cracks and porosity in the weld. If possible, magnetic particle or penetrant testing should be performed to confirm the internal quality. Check whether the bucket is deformed; the flatness of the bottom plate can be measured on a platform. Assemble it on the excavator and run it for trial operation to observe whether there are any abnormal noises or vibrations.

What material is the most durable for a shovel bucket?

Common materials include Q345 high-strength steel plates, NM400 wear-resistant steel plates, and high-manganese steel castings. NM400 offers good cost-effectiveness for earthmoving operations, while high-manganese steel or manganese steel composite plates are recommended for rock excavation. Yuezheng Casting will recommend suitable material combinations based on the customer's actual working conditions, finding the optimal balance between wear resistance and toughness to ensure service life while controlling manufacturing costs.

At what point should the bucket teeth be worn down before they need to be replaced?

When the bucket teeth are worn down by more than 40% of their original length, or when the tooth tips become blunt and digging resistance increases significantly, they should be replaced. Continuing to use them will not only be inefficient but will also increase the stress on the tooth holder, easily causing it to break. It is recommended to replace them in groups, rather than waiting until a particular tooth is completely worn down, to maintain a balanced digging force.

Will the repaired bucket achieve its original performance?

This depends on the extent of the damage and the repair process. If it's just bushing wear or pin weld repair, and the operation is done correctly, it can restore performance close to the original. However, if the bottom plate has a large area of ​​wear and is repaired by welding, the strength and wear resistance will definitely not be as good as a new bucket; it can generally only be restored to about 70%-80%. Therefore, repair is more suitable as a means to extend service life than a long-term solution.