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Machinery SpecialistForestry Attachment Guide
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Which attachments will your machine actually run?

Most disappointing attachment purchases trace back to a buyer who knew the machine weight and guessed the other two numbers. Enter all three and the shortlist writes itself.

The three numbers

Read it off the machine plate, not the brochure.

Circuits fitted

4of eight categories suit this 8 t carrier at 70 L/min with the circuits you have listed. Add a case drain or a second circuit and the list changes.
  • 04Forestry MulchersCarrier sits mid-range for 1–30 t, and the circuit is available.
  • 07Mechanical PruningCarrier sits mid-range for 2–20 t, and the circuit is available.
  • 08Tillage and Ground PreparationCarrier sits mid-range for 2–20 t, and the circuit is available.
  • 01Tree ShearsInside the 2–50 t range but near a bound. Model choice matters more than usual here.
  • 03Stump GrindersNeeds hammer line + case drain, which you have not listed on this machine.
  • 05Grapple SawsNeeds dual circuit, which you have not listed on this machine.
  • 02Stump CuttersPublished range is 11.5–28 t. A 8 t carrier sits outside it.
  • 06Log and Forestry GrabsPublished range is 13–25 t. A 8 t carrier sits outside it.

The circuit is the constraint, not the weight

Forestry attachments differ sharply in what they demand from the hydraulic circuit, and a machine inside the published weight band still cannot run a tool whose circuit it does not have. These are the four configurations, drawn to the same scale.

The four forestry attachment hydraulic circuit typesSingle-acting runs one line between carrier and tool. Hammer line plus case drain adds a third, low-pressure return that takes motor leakage back to tank. Double-acting runs two lines so the tool can be powered open and closed. Dual circuit runs three, separating the saw supply from the grapple and rotation supply.CARRIERTOOLSINGLE-ACTINGCARRIERTOOLCASE DRAINHAMMER LINE + CASE DRAINCARRIERTOOLDOUBLE-ACTINGCARRIERTOOLDUAL CIRCUIT

Single-acting

Oil out, oil back, one direction

Mulchers, most trimmers

Hammer line + case drain

Third low-pressure line returns motor leakage to tank

Grinders, cutters, piston-motor tools

Double-acting

Powered both ways, so the tool opens and closes

Grabs, shears, pruners

Dual circuit

Saw line plus a separate grapple and rotation supply

Grapple saws

Every published carrier range on one axis

Carrier weight, tonnes

Published operating machine ranges, plotted on a log scale so the detail below ten tonnes stays readable. Find your machine on the axis and read down.

12510203050

How this is calculated

Carrier range is the hard gate

Published operating machine ranges come from the manufacturer figures quoted in each category guide. Outside the range means outside the range: undersize the carrier and you get tip-over risk, hydraulic starvation and a slow tool; oversize it and you overload the attachment structure until something cracks.

Circuit availability is the second gate

Each category needs a specific circuit — single-acting, hammer line plus case drain, double-acting, or dual. If you have not listed that circuit on the machine, the category is excluded rather than flagged, because fitting one is a workshop job with a real cost.

Flow windows are indicative

Flow narrows the shortlist, it does not replace a spec sheet. The one figure published in these guides is the OMEF GS grapple saw range, which runs from 15 to 50 L/min on the smallest model up to 160 L/min on the largest. Confirm the model-specific figure before you sign.

Send these numbers for a shortlist →Full compatibility matrix

Frequently asked questions

01

What is auxiliary hydraulic flow on an excavator?

The oil volume, in litres per minute, that the machine can send to an attachment circuit. It sets how fast a rotor, saw or motor actually runs. Flow sets speed; working pressure sets the force the tool can develop. An attachment supplied with too little flow does not fail dramatically, it just runs slowly enough to destroy the economics of the job.
02

Where do I find my excavator's auxiliary flow figure?

The machine plate, or the operator's manual for your specific configuration. Avoid the sales brochure, which often quotes maximum available pump flow rather than what is actually plumbed to the auxiliary circuit on your machine. If no reliable figure exists, a hydraulic technician can measure it with a flow meter in under an hour, and it is worth doing before a purchase rather than after.
03

What is a case drain and do I need one?

A third, low-pressure return line that takes internal leakage from a piston motor back to tank. Piston motors usually need one — grinders and cutters typically do. Running without it builds case pressure and kills motor seals, often inside a season, and it is rarely covered by warranty.
04

Can I add a circuit to my machine?

Usually yes, and it is a workshop job with a real cost that belongs in your purchase comparison. Adding a simple hammer line is straightforward; adding a second auxiliary circuit with solenoid control for a dual-circuit tool such as a grapple saw is more involved. Get that quote before you commit to the attachment.
05

Why does the calculator exclude a category instead of warning about it?

Because fitting a circuit is a real cost with a real lead time, not a footnote. If you have not listed a circuit on the machine, any attachment needing it is not available to you today, and treating that as a soft warning encourages buyers to discover the cost after they have committed.
06

How accurate are the flow windows used here?

They are indicative and labelled as such. The one flow figure published in these guides is the OMEF GS grapple saw range, which runs from 15 to 50 L/min on the smallest model up to 160 L/min on the largest. The windows narrow a shortlist; they do not replace a model-specific spec sheet, and nothing on this site invents a number to look more precise than it is.
07

My machine is right at the edge of a published range. What should I do?

Treat it as a model-selection question rather than a yes-or-no question. Inside a published range the correct model is set by your routine working diameter and your lift capacity at working radius, not by machine weight. At a boundary those two checks decide it, and a supplier who will not do that arithmetic with you is worth being cautious about.
Frequently asked questions

Where to go next

Carrier size guideThe same question answered band by band, with what opens up at each size.
What attachments costOnce you know what fits, what it costs to own and run.
GlossaryCase drain, hammer line, dual circuit and the rest, defined plainly.