OMEF CS400 and CS400H forestry pruners

This page covers two machines, and the first job is to keep them apart. The CS400 weighs 550 kg, cuts 400 mm and is published for 10 to 24 tonne carriers. The CS400H weighs 570 kg, cuts 420 mm and starts at 12 tonnes. Everything else is common: 200 to 250 bar, 50 to 100 L/min, 360 degree rotation, two double-acting lines and no holding grapple. Where a figure below applies to only one of them, it is named.

	CS400	CS400H
Maximum cut	400 mm	420 mm
Head weight	550 kg	570 kg
Carrier band	10–24 t	12–24 t

The 20 mm of extra capacity is a narrow reason to change models. The carrier is the better reason: if the fleet starts at 10 or 11 tonnes, the CS400 is the only one of the pair published for it, and choosing the H then forces a machine decision that costs far more than the difference in diameter.

The hydraulic requirement, in full

Every head in the CS family needs two independent double-acting circuits. One drives the cutting cylinder in both directions, so the jaw closes under pressure and opens under pressure rather than waiting on a spring or on gravity. The other drives the 360 degree rotation, which also has to be powered both ways because a head that can only turn one direction winds its hoses up and stops being useful in a canopy. Two functions, both reversible, both live at the same time: that is what “two double-acting lines” means in practice, and it is the specification most often missed at quotation.

Three things follow from it. First, the carrier needs the plumbing. Many excavators leave the dealer with a single auxiliary circuit intended for a breaker, which is one function and frequently single-acting. A second circuit fitted at build is inexpensive; retro-fitting valve, hoses, boom lines and cab controls afterwards is not, and on a rental or short-term machine it may not be possible at all. Where a second circuit genuinely cannot be added, a diverter valve can share one circuit between cut and rotation, at the cost of not being able to do both at once and of an extra control step for the operator. Confirm with Machinery Specialist that the diverter arrangement suits the head before assuming it will.

Second, the pressure window is tighter here than lower in the family. The CS400 and CS400H want 200 to 250 bar, where the smaller heads start at 180. A carrier relieving at 190 bar will run a CS300 perfectly well and leave these heads short of force in hard wood, and relief settings are frequently left wherever the last attachment wanted them. Ask for the measured auxiliary relief on the specific machine, not the class figure from the brochure.

Third, flow at 50 to 100 L/min sets cycle speed and heat. A 12 tonne machine delivering 60 L/min cuts the same diameter as a 20 tonne machine at 100, but it closes and rotates more slowly, and continuous pruning work with a head turning most of the day is a steady thermal load on the carrier’s return circuit. In an Australian summer that matters; the hydraulic cooling guide covers when an auxiliary cooler earns its place, and the hydraulic matching guide covers the matching method generally.

Hydraulic items to settle in writing

• Two independent double-acting circuits, or a diverter arrangement confirmed as suitable for this head
• Measured auxiliary relief pressure on the specific carrier, inside 200 to 250 bar
• Continuous available flow inside 50 to 100 L/min at working engine speed
• Cab controls assigned for cut and rotation, with proportional control on rotation if available
• Hose routing through the rotation proven for continuous turning in both directions
• Return line size and oil cooling assessed for summer work

Mass at reach is the other constraint

Five hundred and fifty or five hundred and seventy kilograms plus a hitch, held out over a road batter or a rail cutting, is a lift chart question before it is a hydraulics question. These are the heads most likely to be paired with a long-reach front, and that pairing is where the chart runs out first: capacity falls with radius far faster than most buyers expect, and the hitch pin loads rise with it. Run the lift chart at the radius the work actually needs, using the delivered weight of the configuration ordered rather than the catalogue figure, and read the 10 to 16 tonne and 16 to 25 tonne class pages for candidate carriers.

What 400 mm class capacity is for

Mature roadside limbs, rail corridor trees inside possession windows, transmission easement clearance, plantation edge and firebreak stems, and storm-damaged hangers. A green hardwood piece 400 mm across and five or six metres long can approach a tonne, and neither head retains it: the cut releases it and gravity places it. The CS300 page works through that trade-off in full, with further detail in the grapple saw guide and the pruner versus grapple saw comparison. On storm work in particular the fall is least predictable exactly when the consequences are worst, which is why storm damage and dangerous trees is usually a gripping job rather than a cutting one. Both published diameters are green-wood maxima; dense hardwood sits below them (maximum versus production diameter, Australian hardwood). No cut figure should ever be read as a safe suspended load, and the usual exclusion zones, WHS procedures and manufacturer instructions apply throughout.

Within the range these are the top of the individual-cut ladder, above the CS100 and CS200 and alongside the continuous TRI and BTD corridor tools, which remain the better answer for kilometres of small regrowth. Whole stems needing directional control are tree shear work. The mechanical pruning guide sets out the ladder, and road corridor clearing and rail corridor vegetation cover how these jobs are usually organised.

On consumables, the blade edge is the number that drives cost at this diameter, with blade bolts, pivot bushes and the cylinder and rotation motor seals behind it. Get those quoted before the order rather than after the first blunt blade, using the approach in the wear parts guide.

Plumbing the carrier properly, not just adequately

Two circuits on the order form is the start. How they are built decides whether the head performs as published.

Hose and fitting size is the first item. A circuit sized for an occasional breaker may run smaller bore than a head drawing up to 100 L/min continuously wants, and undersized lines show up as pressure lost between the pump and the tool, heat generated in the hoses, and a cut that feels soft at the top of the diameter range even though the relief setting is correct. Ask for the line sizes and the fitting type down the boom and dipper, not just the flow figure at the pump.

Control is the second. Rotation on a proportional control behaves completely differently from rotation on a switched one. Proportional lets the operator creep the head into position and stop it square against a limb; switched turns full speed or not at all, and the difference over a day of presenting a blade to large wood is real. Where the carrier’s joystick roller can be assigned to rotation and a foot pedal or second roller to the cut, the operator keeps both hands available for boom and slew.

Third, the return path. A head cycling a large cylinder and a rotation motor puts heat into the oil steadily, and on a 12 tonne machine it goes back through a cooler sized for digging duty. Watch oil temperature across a full shift in summer rather than a demonstration hour, and read the cooling guide before committing to a long hot-season program. Restricted or undersized return lines make this worse and are a common retro-fit shortcut.

Finally, ask what happens when the head is off the machine. Couplers left uncapped in a dusty corridor are how contamination gets into a circuit, and on a tool with a rotation motor and a large cylinder the cost of that is measured in seals and downtime rather than in hoses.

Two machines, one order: getting the paperwork right

Because this page covers a pair, the order needs to be unambiguous. State the model, the cut, the weight and the carrier the head is being matched to, because a quotation that says only “CS400 series” leaves both the 20 mm and the 20 kg in doubt, and the 20 kg is the one that shows up in the lift chart check. Ask specifically for the delivered mass of the configuration being supplied, including the bracket, the hitch and any guarding, rather than the catalogue head weight.

State these on the purchase order

• Model named as CS400 or CS400H, not as a series
• Published cut for the model ordered: 400 mm or 420 mm
• Delivered mass including bracket, hitch and guarding, in writing
• Carrier make, model and operating weight the head is matched to
• Confirmation that the carrier band covers that machine (10 t for the CS400, 12 t for the CS400H)

Transport, float and the size of the day

A 24 tonne excavator with a long-reach front and a 570 kg head on it is a float movement with its own planning, permits and cost, and on corridor work it is often the item that decides whether a job is worth taking. That is a different world from the smaller heads in the family, and it changes the economics: a machine this size wants continuous work in one place rather than scattered jobs across a district. The transport and mobilisation guide covers the practical side, and the tender rate guide covers how to carry mobilisation into a rate rather than absorbing it.

The same logic applies to ownership. Buying a head at this end of the range usually implies either an existing 10 to 24 tonne machine with spare hours or a contract long enough to justify one, and where neither is true the hire versus buy guide and the total cost of ownership guide are the right places to test the case. On a used purchase, look hardest at the pivot area and the blade seat, since a head that has lived at the top of its capacity in hardwood shows wear there before anywhere else; the used attachment inspection guide has the method.

Storm work, with a caveat

Storm damage and dangerous tree work is listed among these heads’ applications, and it deserves a qualification rather than a recommendation. A wind-damaged tree carries stored energy in bent and partly failed wood, and the direction a piece travels when released is far less predictable than in sound timber. A head that cuts and lets go is at its weakest exactly there. Where a hanger or a partly failed stem has to be taken down in a controlled way, gripping first is the safer approach, and that is grapple saw territory. Where the work is reducing already fallen material, or taking sound limbs back from a damaged crown into a clear zone, the CS400 does it quickly and on a carrier that can also move the debris.

Frequently asked questions