Quick Coupler or Pin-On? How to Measure Excavator Attachment Fitment

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Many attachment problems on site have nothing to do with the attachment itself. They start when the mounting is assumed: "it's an S60, I think", or "pins are about 60 mm". A breaker, bucket, or auger that is right for the job is still the wrong buy if it does not lock safely onto the machine.

This guide explains how to tell which mounting your excavator uses, what to measure on a quick coupler or a pin-on dipper, and which numbers and photos to send so a supplier can confirm fitment before anything is ordered.

Definitions

  • Carrier: the excavator (or backhoe, loader, or other machine) the attachment runs on.
  • Dipper (stick, arm): the arm section the attachment hangs from.
  • Pin-on (direct pin): the attachment is held by two pins straight through the dipper and the link. Changing it means knocking the pins out.
  • Quick coupler (quick hitch): a plate between the dipper and the attachment that locks onto a matching bracket on the attachment, so it can be changed in minutes.
  • Top bracket (attachment bracket): the part of the attachment that mates with the coupler or the pins. On many hydraulic hammers it is a separate, bolted part.
  • Pin centres: the centre-to-centre distance between the two mounting pins.

Step 1: Work out which mounting you have

Stand beside the end of the dipper and look at what sits between the arm and the attachment.

  • Nothing in between: the dipper and link pins go straight through the attachment's ears. That is pin-on.
  • A plate with a locking mechanism (a wedge, a hook and locking pin, or a hydraulic lock): that is a quick coupler. Look for a cast or stamped size or model marking and the maker's plate, usually on the side of the coupler body.
  • A rotating unit with a coupler underneath: that is a tiltrotator. The lower coupler is what the attachment must match, not the upper one.

Common quick-coupler families in Europe include S-type couplers (S40, S45, S50, S60, S70 and others), fully hydraulic systems such as OilQuick, Lehnhoff, and many make-specific or regional pin-grab couplers. Within one S-type size, brackets from different makers are designed to interchange, but the size has to match exactly. An S60 bracket does not fit an S70 coupler.

Step 2: If you run a quick coupler, record these details

  • Coupler make and model from its own plate, plus the size marking (for example S60, or the OilQuick model).
  • Locking type: mechanical or hydraulic locking, and whether it has a visible lock indicator.
  • Hydraulic connections through the coupler: fully hydraulic couplers can connect the attachment's hoses automatically, but only when the attachment's top plate carries the matching couplings in the right positions.
  • The coupler maker's approval for the attachment type. Hammers put repeated shock loads through the coupler. Check that the coupler's manual allows breaker use at the hammer weight you plan to run.

Step 3: If you run pin-on, measure these five things

Pin-on dimensions vary by excavator make, model, and year, and sometimes between two machines of the same model with different dippers. Measure the machine rather than trusting a chart.

  1. Pin diameter: measure each pin with a calliper on an unworn section, not at a worn or damaged spot. Note if the dipper pin and link pin differ.
  2. Pin centres: the centre-to-centre distance between the two pin holes, with the attachment removed or the pins in place.
  3. Inside ear width: the inside distance between the attachment's mounting ears, which has to clear the dipper and link.
  4. Dipper and link width: the outside width of the dipper tip and the link where the pins pass through. Shims or spacers make up small differences.
  5. Pin length and retention: overall length and how each pin is held (bolt, collar, or retaining ring).

Note any visible wear: oval pin holes, worn bushings, or loose pins. Wear changes what a new attachment will feel like on the machine and is worth fixing before you fit one.

Step 4: Check weight and hydraulics against the carrier

A quick coupler adds weight at the end of the arm and moves the attachment further from the dipper pin. That reduces the usable lifting and breakout capacity, so an attachment that is fine on a pin-on machine can be too heavy for the same carrier with a coupler. When you ask for a quote, give the carrier's operating weight as configured, the coupler weight if you know it, and the auxiliary hydraulic flow and pressure settings. For hammers, also say whether the return line goes directly to tank.

Changing from pin-on to a coupler, or the other way round

  • Hammers: the top bracket is often bolted to the hammer body, so a hammer can usually be moved to a different mounting with a new bracket instead of a new hammer. Confirm the bracket matches the hammer model as well as the coupler.
  • Buckets and other attachments: a pin-on bucket generally needs a bracket conversion or a different bucket to run on a coupler. Ask whether conversion is practical before you plan on it.
  • Safety: quick couplers must lock positively, and the operator must be able to confirm the lock. Couplers placed on the EU market should come with a CE declaration and the maker's instructions. Keep them with the machine.

The photo set to send with a fitment enquiry

  1. Side view of the dipper end with the attachment fitted
  2. The coupler's maker plate and size marking, or the bare dipper end for pin-on
  3. Pin diameter with a calliper in the shot
  4. Pin centres with a tape measure across both pins
  5. The attachment's top bracket or mounting ears, from above and from the side
  6. The excavator's ID plate

Common mounting mistakes

  • Ordering by machine class. Two 8 t excavators from different makers can have different pins, centres, and coupler sizes.
  • Reading the coupler size from memory. Couplers get swapped between machines. Read the marking on the one fitted today.
  • Measuring a worn pin. Measure an unworn section, or a new pin if you have one.
  • Forgetting the tiltrotator. On a tiltrotator, the attachment mates with the lower coupler.
  • Ignoring the coupler's limits. Not every coupler is approved for every hammer weight.

FAQ: excavator couplers and pin-on mounts

How do I know which quick coupler size I have?

Look for a cast or stamped marking and the maker's plate on the coupler body. If there is none, send photos plus the pin diameter and pin centres of the coupler's own top pins, and a supplier can usually narrow it down.

Are S-type couplers interchangeable between makers?

Within the same size, S-type brackets are designed to fit couplers from different makers. Different sizes do not interchange, and wear on old brackets can still cause a poor fit.

Can I put a hydraulic hammer on a quick coupler?

Often yes, with a top bracket that matches the coupler, as long as the coupler maker allows breaker use at that hammer weight and the carrier can handle the combined weight.

Do I need exact pin measurements for a pin-on hammer or bucket?

Yes. Pin diameter, pin centres, and ear and dipper widths decide whether the attachment fits. A small difference can sometimes be shimmed, but a wrong pin size or centre distance cannot.

Does Thunderline make couplers or brackets?

No. Thunderline OÜ is an independent aftermarket dealer, not an OEM, and brand names are used only to describe fitment. Send your measurements and we will tell you plainly whether we can match the mounting.

Next step

Choosing a new hammer? Start with how to find the right hammer. Replacing or servicing one you already own? See how to identify a hydraulic hammer from its data plate. With your measurements and photos ready, request a fitment check or email hello@thunderline.eu. More buyer guides are on our Guides page.

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