Small Excavator · 1st of 5

Small Excavator Bucket Cylinder

The tip of the spear. The bucket cylinder curls the bucket teeth into the earth, scoops the load, and dumps it — 8–15 times per minute, hour after hour. The smallest cylinder on the excavator, but the one that hits the ground hardest and cycles the fastest.

50–105mmBore

255 KNMax Thrust

29.4 MPaPressure

≤1,000mmStroke

The Digging Cycle — 7,000 Curls per Hour at the Cutting Edge

Bucket cylinder controlling curl action during digging

Every excavator digging cycle follows the same sequence: the boom lowers the stick into the trench, the stick pushes the bucket forward, and then the bucket cylinder curls — rolling the bucket teeth upward through the soil to fill the bucket. The boom lifts, the machine swings to the dump truck, and the bucket cylinder extends to dump the load. Swing back, lower, and repeat.

A skilled operator on a small excavator completes 8–15 digging cycles per minute. Each cycle requires one full extension and one full retraction of the bucket cylinder — two complete strokes. At 12 cycles per minute, that is 24 strokes per minute, 1,440 per hour, and up to 7,000 per 5-hour operating shift. The bucket cylinder is the fastest-cycling cylinder on the excavator — significantly more than the stick (#2) or boom (#3), which make smaller, slower movements during each cycle.

Korea Ever-Power manufactures the bucket cylinder as the first of five small excavator hydraulic cylinders — designed for the high-speed, high-impact demands of continuous digging.

Technical Specifications

Parameter	Specification
Product	Small Excavator Bucket Cylinder
Function	Control the action of the bucket (curl / dump)
Bore Diameter	50 mm – 105 mm
Rod Diameter	25 mm – 70 mm
Stroke	≤ 1,000 mm
Max Thrust	255 KN (bore 105 mm / 29.4 MPa)
Application	Small Excavator (1–10 tonne class)
Certification	ISO 9001 · 100% hydrostatic tested

Impact, Debris, and Direct Ground Contact — The Harshest Position on the Excavator

The boom cylinder (#3) sits high on the machine, protected from ground contact. The stick cylinder (#2) is at mid-height, partially shielded. The bucket cylinder is at the bottom — centimetres from the cutting edge, directly exposed to the digging face:

Rock strikes — direct impact on barrel and rod

When the bucket hits a buried rock or concrete, the shock travels through the bucket linkage directly to the bucket cylinder. The rod and barrel absorb the full deceleration impulse — creating instantaneous pressure spikes that can reach 2–3× the normal working pressure. The barrel wall thickness and rod diameter are designed with impact safety factors that exceed the static pressure rating.

Debris packing — soil and stones around the cylinder

During digging, soil, mud, gravel, and small rocks pack around the bucket cylinder as it operates at the bottom of the trench. This debris grinds against the rod chrome surface with every stroke — a continuous abrasive attack that no other excavator cylinder experiences at the same intensity. The wiper seal must clear this compacted debris on every retraction stroke. Korea Ever-Power uses heavy-duty double-lip wipers with hardened scraper edges for the bucket cylinder position.

Water and mud immersion — underwater excavation

Small excavators frequently work in wet conditions — digging drainage ditches, clearing waterways, excavating below the water table. The bucket cylinder may operate partially or fully submerged in muddy water. The rod seal, wiper, and all external surfaces must resist prolonged water contact without corrosion or seal degradation. Contact the Korea Ever-Power engineering team for wet-environment bucket cylinder specifications.

Three Cylinders, One Arm — Bucket, Stick, and Boom Working Together

The small excavator's digging arm is a three-link kinematic chain — each link powered by its own cylinder, each with different bore, force, and speed requirements:

Cylinder	Bore	Thrust	Function	Character
Bucket (#1)	50–105	255 KN	Curl / dump	Fastest, most exposed
Stick (#2)	50–115	305 KN	Reach / retract	Depth controller
Boom (#3)	50–125	361 KN	Lift / lower	Heavy lifter

Korea Ever-Power supplies all three cylinders as a matched set — engineered for the same excavator model's hydraulic system, pressure rating, and operating environment.

Small excavator bucket cylinder working in trench

Manufacturing Process

Korea Ever-Power excavator bucket cylinder production

The bore (50–105 mm) is honed to Ra 0.2–0.4 µm. Chrome plating is 50–80 µm — the heavy end for excavators working in rocky or abrasive soil. The rod eye and barrel trunnion are forged and machined (not welded tube-end caps) to resist the high-frequency impact loading from bucket strikes against buried obstacles. All welds are full-penetration and ultrasonically inspected.

Seals are polyurethane piston seal + NBR rod seal + heavy-duty double-lip wiper with hardened scraper, rated for -30 °C to +80 °C. The double-lip wiper is critical for the bucket position — a single-lip design cannot reliably clear compacted soil and gravel from the rod surface at the cycling speeds the bucket cylinder demands.

Every bucket cylinder is hydrostatic tested at 1.5× rated pressure (44.1 MPa) and stroke-tested under no-load and loaded conditions for smooth operation without stick-slip across the full stroke range.

OEM & ODM

What You Provide

Excavator model and operating weight class, bucket size and weight, bucket linkage geometry (pivot points, lever arms), required curl force, bore/rod/stroke or force requirement, system pressure, pin diameters, and the bucket linkage assembly drawing showing all pivot centres and clearance envelopes.

What the Factory Delivers

Engineering drawing with bore, rod (forged eye), stroke, impact-rated barrel wall, double-lip wiper specification, chrome plating detail, and mounting dimensions. Hydrostatic + full-stroke functional test. Seal kits. Browse the mobile machinery hydraulic cylinder family and the Korea Ever-Power catalogue.

Korea Ever-Power workshop

FAQ

Why does the bucket cylinder have the smallest bore on the excavator?

Because the bucket is the lightest component in the arm assembly. The bucket plus its contents weighs less than the stick, and far less than the boom. The curl force to rotate the bucket through the soil is lower than the force needed to push the stick or lift the boom — so a smaller bore (lower force) is sufficient. The bucket cylinder compensates with speed — it cycles faster than the other two.

What is the most common failure mode for the bucket cylinder?

Rod seal leakage caused by rod chrome damage. The bucket cylinder's rod is exposed to direct abrasive contact with soil, gravel, and rock debris — far more than the stick or boom cylinders. Chrome scoring allows contaminated oil to bypass the rod seal, leading to external leakage. Korea Ever-Power's heavy-duty double-lip wiper with hardened scraper significantly reduces the debris that reaches the rod seal, extending seal life by 30–50% compared to a standard single-lip design.

Can Korea Ever-Power supply all three digging-arm cylinders as a set?

Yes — bucket (#1), stick (#2), and boom (#3) cylinders are available as a matched set for the same excavator model, plus the bulldozing cylinder (#4) and rotary actuator (#5) for the complete small excavator hydraulic package. Browse telescopic cylinders and forklift cylinders for other compact machine cylinder applications.