Attachment answers / Sizing & fitment
How do I know what pin size my excavator uses?
Short answer
Check the OEM spec sheet first - bucket pin diameter is listed with the linkage dimensions. Otherwise measure the pin with a caliper on an unworn section. Weight class predicts it: 1-2 t uses 25-30 mm, 4-6.5 t 45 mm, 16-25 t 80 mm.
Last reviewed August 2026 · Quarrymark Attachments sales engineering desk
Pin diameter is the single dimension that most often turns a delivered attachment into a freight claim, and it is also the easiest to establish. There are three places to look, in order of reliability.
1. The OEM spec sheet
Manufacturer spec sheets for excavators and mini excavators list bucket linkage dimensions, usually as bucket pin diameter, link pin diameter, pin-to-pin centre distance and dipper (stick) width. This is the authoritative source and it costs nothing. Search the model number plus the words bucket pin diameter, or ask your dealer's parts counter, who can pull it from the machine's serial number in a minute.
2. The pin itself
Pull the bucket, clean the pin, and measure the outside diameter with a caliper on a section that has not been running in a bushing. Worn pins measure undersize - a nominal 45 mm pin with 200 hours of neglected greasing can mike out at 43 mm - so measuring at the wear band will send you to the wrong band. Measure at the retained end, near the head, where the pin is not loaded.
Metric and imperial both appear in the field. Attachments in our catalog are specified in millimetres because that is how the OEMs specify the linkage. A 2 in. pin is 50.8 mm and mates with a 50 mm bore only with a hone; do not assume a rounding is safe.
3. The weight class, as a cross-check
Because manufacturers scale linkage with machine size, operating weight predicts pin diameter tightly. Across the 94 machines in our fitment database, the pattern is consistent enough to use as a sanity check on a measurement: if your 5 t machine measures 80 mm, you have measured something other than the bucket pin.
Pins are only half the mount
Pin diameter gets quoted because it is one number, but a bucket has to clear the stick as well as accept the pin. You also need the dipper width - the outside width of the stick where it sits between the bucket ears - and the pin-to-pin centre distance between the bucket pin and the link pin. A bucket with the right pin bore and the wrong ear spacing will not go on, and a bucket with the wrong pin-to-pin distance will go on and then bind at full curl.
| Operating weight | Typical pin Ø | Example machines |
|---|---|---|
| 1.0 t | 25 mm | Kubota K008-3 |
| 1.7-2.0 t | 30 mm | CAT 301.7 CR, Kubota U17, Bobcat E20 |
| 2.6-2.8 t | 35 mm | CAT 302.7 CR, John Deere 26G, Bobcat E26 |
| 3.1-3.7 t | 38-40 mm | John Deere 35G, Kubota U35-4, Bobcat E35 |
| 4.2-6.3 t | 45 mm | Kubota KX057-4, John Deere 60G, CAT 306 CR |
| 8.5-9.8 t | 50 mm | CAT 308 CR, John Deere 85G, Bobcat E88 |
| 13.6-15.7 t | 65 mm | CAT 313, CAT 315, John Deere 135G |
| 22-25 t | 80 mm | CAT 320, CAT 323, John Deere 210G |
| 28-30 t | 90 mm | CAT 326, CAT 330 |
| 36 t+ | 100 mm | CAT 336, John Deere 350G |
Operating weights are from the manufacturers' own spec sheets. Pin diameters are the typical value for the class and are shown here to check a measurement against, not to replace one.
My machine has two different pin sizes. Is that normal?
Yes. The bucket pin and the link (H-link) pin are frequently different diameters, and backhoe loaders very often run two sizes - our backhoe buckets are listed as 45/38 mm, 50/45 mm and 55/50 mm for exactly that reason. Quote both.
Does a quick coupler change the pin size I order?
It changes what you order entirely. With a coupler fitted, the attachment mounts to the coupler, not to the stick, so you order by coupler style - Bobcat X-Change, John Deere Wedge Lock, Kubota Wedge Lock - and the machine's own pin diameter stops mattering.
What if my model is not in your machine list?
Send us the operating weight and a photo of the stick end with a tape across the pin. Weight class plus one measurement is enough for us to identify the right band in almost every case.
