Short answer
A bracket is the piece that joins an attachment to a machine, and the reason it is not standard is simple: what it joins to is not standard either. Every machine maker uses a different boom end width, pin diameter and pin spacing, and they differ between weight classes from the same maker too. So a bracket is made to the MACHINE’s dimensions rather than the attachment’s, and when the wrong dimensions are given the resulting problem is structural rather than cosmetic: a joint with play moves on every blow and enlarges the pin bore. This guide covers why those dimensions are asked for together and what a wrong bracket costs.
Which dimensions are asked for?
These five are given together because each verifies the others. Giving pin diameter alone is like stating a shoe size without the width.
- Pin diameter: the diameter of the pin joining the attachment to the boom. Not sufficient on its own, but nothing can be done without it.
- Pin spacing (centre to centre): the distance between the two pin bores. Get this wrong and the bracket will not sit at all.
- Boom end width: the thickness of the boom end that goes between the bracket ears. Made narrow it will not enter; made wide it leaves play and the joint moves.
- Machine make, model and where possible the serial number: the dimensions are cross checked against these. The same model may have changed between years.
- If a quick coupler is used, its type and dimensions: the bracket is then made to the coupler rather than to the machine.
Three consequences of a wrong bracket
The first and commonest is play. If boom end width was given too large, a gap is left between the ears. That gap closes and opens on every blow; the pin bore goes oval and over time both bracket and boom end suffer.
The second is misalignment. If pin spacing is out by a few millimetres, the pins go in under force and the attachment sits slightly askew to the boom axis. On a breaker that skew converts directly into lateral load and accelerates bushing wear.
The third is the attempt at repair: welding the bracket straight on site, or shimming the gap. Both are temporary and both open the attachment’s warranty assessment to argument.
Do not shim the play
Closing the gap between boom end and bracket ears with plate or shims is a common field fix and appears to work. But on an impact attachment that shim does not stay put; it slides, it thins, and the play comes back. Meanwhile the pin bore keeps enlarging. The right answer is to bring the bracket to dimension.
How a quick coupler changes this
With a quick coupler, the bracket is made to the coupler rather than to the machine. For a fleet that is a considerable simplification: every machine with the same coupler can take the same attachment.
But it creates a dependency too: if the coupler type changes, every attachment’s bracket has to be redone. Which is why the coupler decision is among those to take early in the fleet plan.
The second point is safety: a coupler is an intermediate part, and every intermediate part means one more connection. That is why confirming the coupler’s safety lock by eye at every fitting has become a rule.
Do and don’t
Do
- Give the five dimensions together: pin diameter, pin spacing, boom end width, machine make and model, serial number.
- Take the dimensions from the machine where possible; the catalogue figure may have changed between years.
- If you use a quick coupler, have the bracket made to the coupler and state that in writing.
- Buy the bracket with the attachment so responsibility stays in one place.
- When you buy a new machine, check bracket compatibility for your existing attachments in advance.
Don't
- Do not order a bracket giving pin diameter alone.
- Do not close play with plate or shims.
- Do not try to correct a bracket by welding it on site.
- Do not accept "roughly fits" when moving to a different machine; a few millimetres turn into lateral load.
- Do not leave bracket dimensions until after the order; that is what lengthens delivery.
What happens when the machine changes?
The attachment stays, the bracket changes. If the new machine’s boom end dimensions differ, existing attachments need new brackets; that is an item usually left out of the machine replacement calculation.
So when a machine renewal is being decided, bracket compatibility for the existing attachment fleet belongs on the table. Staying within the same maker and the same weight class can bring that item close to zero.
To see which attachment suits which machine you can use the carrier selection tool, or write to us with the model codes.