The bucket pin is the core pivot pin connecting the bucket to the boom/arm of an excavator. Its core principle is to bear excavation loads and transmit hydraulic thrust via a high-strength shaft body, achieve low-friction rotation through lubrication and sealing, and ensure reliable articulation with positioning structures.

I. Typical Core Structure

1. Shaft Body: Made of high-strength alloy steel (e.g., 42CrMo), it withstands enormous bending and shear forces.

2. Lubrication System: Grease hole → Main oil passage → Auxiliary oil passage → Threaded oil groove → Oil storage element (cotton wick/yarn tape) → Friction surface, forming a continuous oil film.

3. Sealing & Dust Protection: Dust-proof groove at the shaft end + sealing ring, which blocks silt and extends service life.

4. Positioning & Anti-dislodgement: Locating ring, pin hole and limit block at the shaft end, preventing axial movement and dislodgement.

II. Complete Working Principle

1. Connection & Positioning

The bucket pin passes through the hinge holes of the bucket and arm, and is fixed at both ends with a locating ring and cotter pin to form a rigid articulation, ensuring coaxiality and axial limiting.

2. Load Transmission (Core)

During excavation, the bucket bears material resistance → the force is transmitted along the arm → the bucket pin withstands huge radial force, bending moment and shear force; the hydraulic cylinder thrust drives the bucket to rotate via the bucket pin, completing excavation, lifting and unloading.

3. Lubrication & Wear Reduction (Key)

• Grease Injection: Grease is injected through the grease hole and flows into the threaded oil groove via the main/auxiliary oil passages.

• Oil Storage: The oil storage element in the groove absorbs grease and forms a uniform oil film between the pin and bushing when saturated.

• Continuous Lubrication: The oil film is continuously consumed during operation, and the oil storage element releases grease steadily, which greatly extends the lubrication cycle and reduces wear.

4. Sealing & Protection

The dust-proof groove and sealing ring at the shaft end block dust, mud and water from entering the friction pair, avoiding abrasive wear and prolonging the service life of the bucket pin and bushing.

5. Rotation & Reset

Driven by hydraulic pressure, the bucket rotates flexibly around the bucket pin; after the operation is completed, it resets under the action of the cylinder and gravity for cyclic operation.