How to Measure Excavator Pins for a Perfect Attachment Fit

Buying an excavator attachment online is easy—until it arrives and the pins don't line up. Returning heavy equipment is expensive and delays your job. To ensure a perfect fit the first time, you need three exact measurements.

Measurement 1: Pin Diameter

This is the thickness of the pins that secure the bucket to the arm. Common sizes are 35mm, 40mm, 45mm, 65mm, and 80mm. Use a set of digital calipers to measure the pin itself, or the inside diameter of the boss (the hole) on your current bucket. Do not use a tape measure—the difference between 40mm and 45mm is tiny but critical.

Measurement 2: Dipper Gap (Inside Width)

Measure the inside distance between the mounting ears (bosses) on the bucket. Your excavator's arm has to fit inside this gap. If the bucket gap is too narrow, the arm won't fit. If it's too wide, the bucket will slop side-to-side (though this can sometimes be fixed with shims).

Measurement 3: Pin Center-to-Center Distance

Measure from the exact center of the front pin hole to the exact center of the rear pin hole. This is especially critical if you use a quick coupler, as couplers have very little tolerance for incorrect center distances.

Pro Tip: If you have a quick coupler, measure the coupler's pickup points, not the machine's arm.