Short answer
Whichever attachment you choose, the first criterion is carrier weight, and it is not open to negotiation. An attachment that is too light for the machine gets crushed by the machine own force and finishes quickly. One that is too heavy loads the boom pins beyond design, cracks the boom, upsets stability and creates a tipping risk. The tonnage figure in a catalogue is a range rather than a single number, because two machines of the same weight behave very differently with different boom lengths and counterweights.
An undersized attachment: money lost quietly
Fitting a small attachment to a big machine looks harmless at first; the machine is simply stronger. The problem is exactly that strength. The excavator can apply more push than the attachment is built to take, and the operator never feels it.
On a breaker this shows as excessive down-force into the body, loading the tie rods and the front head. On shears and pulverisers the jaw mechanism is strained. On a crusher bucket the body and mounting ears crack.
None of this happens in a day, so the cause is never noticed. The attachment gets recorded as "poor quality" when in fact the machine crushed it.
An oversized attachment: machine damage and a safety risk
The opposite error is more dangerous. A heavy attachment puts loads into the boom pins and the boom structure that they were not designed for. Cracked booms and worn pins are the direct result.
More importantly, it is a stability problem. The counterweight of an excavator is calculated around a certain weight at the end of the boom. With a heavy attachment the machine sits forward, and with the boom extended and slewed to the side the tipping risk is real.
So an attachment beyond the tonnage range is not something to use "with a bit of care". The upper end of the range is a safety limit.
Why the figure is a range
Catalogue tonnage is a range rather than a single number because two excavators of the same weight are not the same machine. A long-boom machine can carry far less at the tip than a short-boom machine of identical tonnage. If you are working near the lower end of the range, a long boom may mean overloading. If you are unsure, tell us your boom configuration as well and we will look at it together.
What to check after tonnage, in order
- Hydraulic match: does the flow and pressure delivered to the attachment line fall within the attachment range?
- Mounting: bracket and pin dimensions must be made for your machine. On HKM attachments the bracket is made to the customer carrier.
- If a quick coupler is used, its own weight adds to the weight at the tip; this is often forgotten.
- How it is worked: at the same tonnage, a machine running continuously in a quarry may need a different choice from one working occasionally.
- Age and condition of the carrier: going to the top of the range on a worn boom is not right.
How to verify
Read the operating weight of your machine from its manual. Two machines of the same model can differ because of cab equipment, track type and counterweight; the plate figure governs.
Enter your tonnage in the selector on this site: from breakers and shears to drum cutters and rippers, you see every model that fits on one screen. Models outside your tonnage never appear, because the tonnage filter is the first criterion.
If you are looking for a breaker, the dedicated breaker tool narrows the list further by taking operating pressure into account as well.