Choosing the Right Finishing Bucket for a Kobelco SK35SR-2

[MikePhua]

The Kobelco SK35SR-2 and Its Compact Excavation Role
The Kobelco SK35SR-2 is a compact short-radius excavator designed for urban construction, landscaping, and utility trenching. With an operating weight around 8,000 lbs and a digging depth of approximately 10 feet, it balances maneuverability with power. Kobelco, a Japanese manufacturer with roots dating back to 1930, has built a reputation for hydraulic efficiency and operator comfort. The SK35SR-2, part of their mini-excavator lineup, features a zero-tail swing design and smooth control response, making it ideal for tight job sites.
One of the most common upgrades for machines in this class is the addition of a finishing bucket—used for grading, backfilling, and smoothing surfaces after excavation. Selecting the right bucket size and style is essential for maximizing productivity and maintaining machine balance.
Terminology Annotation
- Finishing Bucket: A wide, shallow bucket designed for grading and cleanup rather than digging.
- Pin-On Style: A bucket mounting method using direct pins rather than quick couplers.
- 40mm Pins: The diameter of the mounting pins, critical for compatibility with the excavator’s linkage.
- Ditching Bucket: A type of finishing bucket optimized for shaping ditches and slopes.
- Clean-Up Bucket: A finishing bucket with a smooth edge, used for final grading and debris removal.
Bucket Width and Machine Compatibility
For the SK35SR-2, bucket width selection is a balance between coverage and control. While a 36-inch bucket may seem sufficient, many operators recommend a 48-inch or even 60-inch bucket for finishing work. The wider bucket allows for fewer passes and a smoother finish, especially when grading driveways, pads, or landscaping contours.
However, going too wide can strain the machine’s hydraulics and reduce breakout force. A 60-inch bucket may be suitable for light material like topsoil or mulch, but not for compacted clay or gravel. The optimal size for most finishing tasks on the SK35SR-2 is 48 inches, offering a good compromise between coverage and control.
Custom Fabrication and Retrofit Options
Some operators choose to fabricate their own finishing buckets, especially when commercial options exceed budget constraints. Building a bucket requires:

• High-strength steel (AR400 or equivalent) for the cutting edge
  
• Reinforced side plates to prevent flexing
  
• Proper pin spacing and diameter (40mm for the SK35SR-2)
  
• Drain holes or slots for wet material
  
• Smooth edge or bolt-on cutting edge for clean grading
  

Fabricators often use existing bucket shells and modify them with wider side extensions. Welding must be done with care to avoid warping the mounting ears or misaligning the pin holes.
Sourcing and Cost Considerations
New finishing buckets for compact excavators typically range from $800 to $1,200 depending on brand and features. Some aftermarket suppliers offer economy models with thinner steel and fewer reinforcements, which may be suitable for occasional use but not for daily grading.
Used buckets can be found at auctions, rental yards, or salvage dealers. When purchasing used:

• Inspect pin holes for elongation
  
• Check for cracks near welds and mounting ears
  
• Verify width and curvature for compatibility
  
• Confirm that the bucket is designed for pin-on mounting, not quick coupler
  

Operators near Pittsburgh, for example, may find regional dealers or fabrication shops willing to build or modify buckets at lower cost than national suppliers.
Hydraulic Fitting Compatibility and Upgrades
While the bucket itself is mechanical, hydraulic compatibility becomes relevant when switching attachments or modifying auxiliary lines. Some machines use ANSI-style fittings, which can be difficult to source in certain regions. Converting to JIC (Joint Industry Council) fittings simplifies maintenance and sourcing.
For the SK35SR-2:

• Identify fitting types on auxiliary lines and valve blocks
  
• Use ORB (O-Ring Boss) adapters to transition to JIC
  
• Replace hoses with standard JIC ends for easier field repair
  
• Label hydraulic lines for function and pressure rating
  

This upgrade is especially useful when adding thumbs, tilt buckets, or other hydraulic attachments that require reliable connections.
Field Anecdotes and Practical Advice
One operator in Saskatchewan built his own 48-inch ditching bucket during winter downtime. He used scrap steel from a retired loader bucket and reinforced the sides with angle iron. After several seasons of use, he reported excellent performance in grading and cleanup, though he noted that the bucket was too heavy for deep trenching.
Another contractor in Pennsylvania emphasized the importance of matching pin diameter and spacing precisely. He once purchased a bucket with 45mm pins, assuming it would fit his 40mm linkage. After hours of grinding and sleeving, he managed to retrofit it—but advised others to measure twice and confirm specs before buying.
Conclusion
Selecting a finishing bucket for the Kobelco SK35SR-2 involves more than just width—it’s about compatibility, durability, and intended use. Whether purchasing new, sourcing used, or fabricating from scratch, operators must consider pin dimensions, hydraulic fittings, and material strength. With the right bucket, the SK35SR-2 transforms from a digging machine into a precision grading tool, capable of leaving a jobsite clean, level, and ready for the next phase. In compact excavation, the final pass is often the most important—and the right bucket makes all the difference.