How to choose the right tree shear for your excavator

Choosing the right tree shear starts with assessing the performance and size class of the base machine. The right attachment makes energy wood harvesting and the clearing of brushwood and building plots efficient. A shear that is too large reduces the machine's stability, compromises work safety and causes premature wear on the boom. A shear that is too small, on the other hand, leaves the excavator's hydraulic capacity unused, which slows down work and increases fuel costs per cubic metre of wood produced.

A well-matched machine combination requires assessing the base machine's operating weight, boom reach, and hydraulic oil flow and operating pressure. When these values match the requirements of the tree shear, cutting cycles stay fast. Work then runs smoothly, even in demanding terrain.

THE EXCAVATOR'S SIZE CLASS DETERMINES THE CHOICE OF TREE SHEAR

For energy wood harvesting, excavators used in earthmoving and forestry contracting are generally divided into three size classes. The structural durability and weight of the attachment must be matched directly to how much load the base machine's boom can withstand without losing stability.

For excavators weighing less than 6 tonnes, the low weight of the shear is the most important selection criterion. The reach of small machines and the lifting capacity of their booms at full extension are limited. A heavy shear reduces the machine's ability to handle a bundle of cut stems and makes work unstable. In this size class, the shear must be lightweight yet sturdy, so that clearing dense brushwood and small trees goes quickly.

For mid-size excavators (6–12 tonnes) and heavier equipment (over 12 tonnes), the tree shear requires considerably more mechanical strength and cutting capacity. Larger machines handle thick trunks and heavier loads, so the attachment's frame and pivot points must withstand heavy torsion.

With the right size class, the machine's centre of gravity stays low and the boom operates along its designed range of motion. This reduces heat build-up in the hydraulic system and spares the base machine's slewing ring from strain.

HYDRAULIC OUTPUT AND CUTTING MECHANISM REQUIREMENTS

In addition to its physical size, the tree shear must be compatible with the excavator's hydraulic system. The attachment's performance depends on two key values: oil flow (litres per minute, l/min) and operating pressure (bar).

Oil flow determines how fast the cutting blade and jaws move. If the base machine's output is too low relative to the shear's cylinder volume, the cutting motion slows down. This increases the time it takes to cut a trunk and reduces productivity. Insufficient pressure, on the other hand, prevents the blade from cutting through thick or fibrous wood in a single stroke, forcing the operator to clamp the wood several times.

In professional use, the blade's cutting geometry and the distribution of clamping force are evaluated. A high-quality blade cuts cleanly through the wood fibres, which prevents the stem from splitting and keeps the cut surface even. When the hydraulic components and the cutting blade work together in balance, the tree shear handles both larger trunks and dense bundles without jamming or interruptions.

CUTTING METHOD AND STRUCTURAL DURABILITY OF THE EQUIPMENT

The choice of cutting method depends on the trees at the work site. Guillotine-type blade cutting relies on clamping force: a fixed or sliding blade is pressed through the trunk by a hydraulic cylinder. This mechanically simple solution has few parts that can wear out or break. Contact with soil or rocks does not compromise the attachment's functionality in the same way as it does with sawing mechanisms. This reduces maintenance downtime and lowers upkeep costs.

When a clean saw cut is required or heavy logs are being handled, a saw grapple offers clear advantages. For energy wood clearing and site clearance, however, guillotine shears still hold their own, as they work reliably even in snow, mud and rocky terrain.

The structural strength of the equipment is based on high-quality steel, protected hydraulic components and precise pin joints. High-strength steel allows for a lightweight frame without compromising durability. A lightweight shear reduces the strain on the excavator's boom and slewing ring. This extends the service life of the base machine and reduces fuel consumption.

FINNISH AXER TREE SHEARS FOR DEMANDING USE

Finnish manufacturer Axer develops and produces attachments for the demanding needs of machine contracting. Its product development is built on a straightforward design, durable materials and a long service life. The range includes a suitable tree shear for excavators of different sizes and for varying working conditions.

For heavy equipment over 12 tonnes, the range includes the more robust Axer 650 K, the HD-reinforced 650 HD K models and the Axer 800 HD K tree shears. In these attachments, the frame material thicknesses and cutting force are dimensioned to handle large bundles and thick timber without bending.