Excavator H-Links & Dogbones Explained
Excavator H-Links & Dogbones Explained
What are excavator H-links and dogbones? Learn how these linkage components work and how to choose quality replacements for your machine.
When operators talk about bucket performance, breakout force, or smooth digging action, they’re usually thinking about the boom and bucket, but the real mechanical magic happens in the bucket linkage, where the H-link and dogbone play a major role.
These two components carry extreme force every single time the bucket curls, lifts, or pries. Understanding how they work (and when to replace them) can save you time, money, and downtime.
This guide breaks it all down in simple, practical terms, whether you're new to heavy equipment or rebuilding your machine’s linkage assembly.
What Is an Excavator H-Link?
An H-link (sometimes called a bucket link) is a heavy steel linkage that connects the outer end of the bucket cylinder to the bucket itself.
It’s shaped somewhat like the letter “H,” with two pin bores on each end designed to transfer force from the hydraulic cylinder through the linkage system.
What the H-Link Does
The H-link is responsible for:
- Transmitting cylinder force to the bucket
- Controlling curl and dump angles
- Maintaining bucket alignment under load
- Supporting the bucket during breakout operations
Because the H-link acts as a structural bridge between moving parts, it must withstand constant, high-pressure stress and rotational motion. That’s why proper fit, hardened bushings, and high-quality steel are absolutely critical.
What Is a “Dogbone” on an Excavator?
The dogbone (also called the “bucket link bar” or “triangle link”) is the connector between the H-link and bucket, typically shaped with a narrow center and wider ends, similar to a dog bone.
It works hand-in-hand with the H-link to provide smooth, powerful movement.
What the Dogbone Does
The dogbone:
- Supports bucket rotation
- Ensures smooth pivoting
- Keeps bucket geometry consistent
- Balances load distribution between linkages
Without a correctly sized dogbone (and matching pins), the bucket won’t track smoothly, and wear will accelerate rapidly.
How H-Links and Dogbones Work Together
Think of the H-link and dogbone as a synchronized pair.
When the hydraulic cylinder extends or retracts:
- Force travels through the bucket cylinder pin.
- That force transfers into the H-link.
- The H-link rotates and pulls against the dogbone.
- The dogbone pivots the bucket through its full curling motion.
If either component wears prematurely, the entire linkage becomes sloppy, noisy, or misaligned.
Signs Your H-Link or Dogbone May Need Replacement
Because these parts handle constant motion and load, they show wear in several predictable ways:
Excessive bucket play
If the bucket rocks even when pins are tight, the link bores may be worn.
Visible ovaling or elongation
Egg-shaped bores are a clear sign the steel has worn beyond tolerance.
Rapid bushing wear
If bushings fail quickly, it’s often the linkage housing that’s out of spec.
Uneven bucket curl
A worn or bent dogbone can cause twisting or dragging during curl operations.
Grease retention issues
If grease escapes or fails to distribute, the bushings may be misaligned.
Choosing Quality Aftermarket Linkage Components
Whether you’re replacing parts on a CAT, Volvo, Deere, Komatsu, or Hitachi machine, high-quality aftermarket linkage components can offer excellent performance at a fraction of OEM pricing.
When selecting replacement H-links and dogbones, look for:
1. OEM-spec hardened steel
Heat-treated alloy steel ensures long-lasting durability.
2. Precision-machined bores
Accurate tolerances reduce pin wear and ensure smooth movement.
3. Complete bushing assemblies included
An H-link bushing assembly saves time and ensures proper fitment.
4. Corrosion-resistant coatings
Gold zinc, phosphate, or powder coatings increase part life.
5. Verified compatibility
Use machine model numbers or pin charts to match sizes perfectly.
Good quality aftermarket linkage parts from trusted manufacturers often match (or exceed) OEM performance, especially when paired with high-grade pins and bushings.
Tips to Extend Linkage Life
To keep your H-link, dogbone, and bucket bushings in top condition:
- Grease daily, especially in high-dirt conditions
- Inspect pins every 250 hours
- Check for side loading or improper bucket use
- Replace damaged seals immediately
- Address bushing wear as soon as you notice slack
Regular maintenance dramatically reduces premature wear and improves bucket response.
Final Thoughts
Excavator H-links and dogbones may seem like simple steel parts, but they play an essential role in your machine’s breakout force, bucket control, and long-term performance. Understanding how they work, and choosing high-quality replacements, helps protect your investment and keep your excavator running smoothly.