Bucket pins take the full digging force of the machine, so they wear, bend and seize over time. Catching a worn pin early is cheap; ignoring it destroys bushings, linkages and eventually the stick itself. This guide covers the standard pin layout on Cat, Komatsu, Hitachi, Doosan and Hyundai excavators, how to measure wear, and how to buy the right pin set the first time.
1. Pin Layout and Sizes on Common Excavators
A standard excavator bucket has three pivot points: the bucket pin (bucket to stick), the link pin (linkage to stick) and the bucket cylinder pin (linkage to cylinder rod). Each has a different diameter, and the sizes scale with machine weight:
| Machine Class | Bucket Pin Ø | Link Pin Ø | Typical Pin Material |
|---|---|---|---|
| Mini excavator (1.5–6 t) | 25–40 mm | 20–35 mm | 4140 / 42CrMo steel, hardened |
| Mid excavator (13–25 t) — Cat 320D, Komatsu PC200, Hitachi ZX200 | 50–70 mm | 40–60 mm | 42CrMo, induction-hardened |
| Large excavator (30–50 t) — Cat 330/336, Komatsu PC300/400 | 70–100 mm | 55–80 mm | 42CrMo, through-hardened |
Doosan DX220, Hyundai R210 and Volvo EC210 all sit in the mid class and share very similar pin diameters — but the pin length and the position of the grease groove and circlip groove differ, so always match the OEM part number rather than measuring diameter alone. Our bucket teeth and pins catalog carries pin sets for these models, plus the teeth and adapters that go on the same bucket.
2. How to Measure Bucket Pin Wear
Pin wear shows up as play in the bucket before it shows as visible damage. Check it the way a used-machine inspector would:
- Rock the bucket by hand — with the bucket on the ground and the machine off, lift the bucket tip. More than 3–5 mm of vertical movement at the tip means measurable pin/bushing wear.
- Measure the pin diameter — remove the pin and measure with a micrometer in two planes. A mid-size pin that has lost 1.5–2 mm of diameter is at replacement point; 0.5 mm is normal wear.
- Check the pin surface — scoring, galling or a flat side means the pin has been running against a seized or worn bushing.
- Grease test — pins that will not take grease through the fitting, or grease that escapes past the seal immediately, usually have a blocked groove or a worn seal ring.
As a rule of thumb, replace pins when the clearance between pin and bushing exceeds roughly 2 mm — that is the point where digging forces start hammering the linkage instead of cutting the ground. For the full checklist on a used machine, see the used machinery inspection checklist.
3. Buying Replacement Bucket Pins: What to Specify
To order the correct pins you need four pieces of information: the machine model and serial range, the OEM pin part numbers, the pin diameter and length (measured if you have the old pins out), and the number of pins plus circlips and grease fittings needed. Where you buy matters:
- OEM from the dealer — exact fit, but expensive and slow; a full set for a 320D can run $400+ and takes weeks.
- Aftermarket from China — same 42CrMo material and hardness when bought from a real manufacturer, at roughly a third of the dealer price. The key is the material cert and the hardness spec (HRC 40–50 is typical for bucket pins).
- Used pins — fine for low-hour machines, but measuring wear on used pins is unreliable; we generally recommend new pins for working machines.
While you are at it, check the tooth material comparison — bucket teeth, adapters and pins wear as a set, and replacing them together avoids a second downtime. Send us your model and OEM numbers and we will quote the complete pin and bushing set, including circlips and grease fittings, with combined freight.
FAQ
Q: How often should excavator bucket pins be replaced?
A: Every 1,500–3,000 operating hours for a working machine, or sooner when tip play exceeds 3–5 mm or pin diameter loss reaches 1.5–2 mm.
Q: What size are the bucket pins on a Cat 320D?
A: The 320D bucket pin is in the 50–70 mm range depending on the bucket and linkage variant; confirm with the OEM part number for your serial range.
Q: Can I replace bucket pins without removing the bucket?
A: Yes — with the bucket lowered to the ground, drive out each pin with a press or torch; you only remove the bucket if the pins are seized.
Q: Does CN Machinery supply bucket pin sets?
A: Yes — pin, bushing, circlip and grease fitting sets for Cat, Komatsu, Hitachi, Doosan and Hyundai excavators, matched by OEM part number.
Need Bucket Pins, Bushings or Teeth?
Send us the machine model and the OEM part numbers — we will confirm the sizes and quote pins, bushings, circlips and teeth for the complete bucket job.
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