OEM Pins vs Attachment Pins

July 28, 2021
There are two types of pins used in the operation of an excavator, and using the wrong type in the wrong place can cost the operator.
Not all excavator pins are the same, and getting it wrong can cost money

Why are there different grades of excavator pins?

A pin’s a pin, right? Only two measurements to consider – length and diameter.

OEM vs bucket pins

But that’s not quite right; there are two types of pins used in excavators, and they’re not interchangeable. Using the wrong pin type can, in fact, cost money and time (which is also money).

Factory, or OEM, pins are the ones that shipped with the excavator. These are made of induction hardened steel. They join the dipper and linkage to the coupler (or in the case of no fitted coupler, directly to the bucket).

Bucket, or attachment pins are fitted to the bucket (or attachment). These are usually medium tensile steel, with no additional hardening.

Why the two types?

The first answer is rotation. The OEM pins pass through the dipper and the linkage and are bolted to the coupler. That means that when the coupler is curled or extended, the pin (fixed to the coupler) rotates inside the hardened bushes of the excavator. These joints must be kept lubricated, and the steel used has to be tough. If mild steel pins were used in this application, they would quickly wear down and the joints loosen, requiring regular pin replacement (and associated downtime).

OEM pins rotate within the hardened bushes of the excavator

Medium tensile steel attachment pins are bolted to the bucket and picked up by the coupler. But rather than rotating in their coupler housings, they’re held fast. Induction hardened steel is not necessary for these pins.

So why not use hardened pins in both applications?

One answer is price; why pay extra for hardened pins when non-hardened are sufficient?

But the main reason, again, has to do with wear. Although the bucket pins are held fast by the coupler, there are still tiny movements when the attachment is jolted or moved. When two types of steel rub together, the weakest of the two will take the wear load. The jaw of the coupler and the face of the safety wedge—which are in direct contact with the pin—while made of tough steel, are not induction hardened. A hardened steel pin will ultimately cause excessive wear in these vital and expensive coupler parts.

You want the much cheaper pins to take the wear

A medium tensile steel pin, on the other hand, will take on any wear – and is much cheaper to replace.

Further Reading

Safe Attachment Changeovers

Safe Attachment Changeovers

Over the years the detach–attach operation of quick couplers has become increasingly foolproof. But there are a number of additional factors that will smooth the process and render it completely safe for everyone concerned.

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Twin-Ram Tilt or Rotary Tilt Coupler?

Twin-Ram Tilt or Rotary Tilt Coupler?

There's no doubt that a tilting coupler offers greater flexibility, but which type of tilt mechanism is best?

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What's best? Tilt Coupler or Tilt Bucket?

What's best? Tilt Coupler or Tilt Bucket?

Flexibility is the key to greater productivity in civil and construction works. And nothing provides more flexibility than being able to tilt a bucket. The question must then be asked, Tilt Coupler or Tilt Bucket?

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