Demolition Shear Product

Overview

A demolition shear is a powerful cutting attachment for dismantling structural steel and reinforced concrete. Unlike breakers or crushers that rely on percussion or grinding, the shear cuts cleanly through material using opposing hardened steel blades meeting in a scissor action. Each blade can be 150–250 mm tall and 400–500 mm wide, driven by a hydraulic cylinder capable of exerting 500–800 tonnes of force. The blades are kept sharp through regular grinding or replacement of the hardened steel or tungsten-carbide cutting edges. The shear mounts to a 30–60 tonne excavator via quick-change coupler and rotates continuously, making it ideal for efficient cutting of multiple members during structural demolition.

How it works

The core mechanism is the Blade Set Assembly. A Fixed Blade is bolted immovably to the Main Frame & Structure. An Moving Blade, pinned on a Blade Pivot Axle at the rear, swings upward and downward over the fixed blade, like a pair of scissors. Both blades have precision-ground Fixed Blade Cutting Edge and Moving Blade Cutting Edge surfaces at matching bevels (typically 30–45 degrees) that slide past one another. The blade edges are hardened tool steel (50–60 HRC) or tungsten carbide for long life.

Material to be cut — a steel column, a reinforcing bar, or a concrete strut — is positioned between the blades. When the excavator operator closes the joystick, a Shearing Cylinder & Drive pressurizes and drives the moving blade downward. As the blade faces approach, they grip the material. The Speed Control & Metering proportional valve limits closing speed to 30–60 mm/s, ensuring smooth, controlled cutting. Once the blades meet and grip the material, the scissors geometry focuses cutting force at the blade edges. The shear force concentrates along a narrow line, penetrating the material faster than any crushing or grinding action could achieve.

The Directional Spool Valve in the Speed Control & Metering assembly responds to the operator's joystick input. A proportional command signal tells the spool to meter pump flow through a Flow Control Cartridge feeding the Cylinder Barrel. The cartridge is a pilot-operated metering valve; it opens only enough to supply the requested closing speed, creating a stable load-sensing loop. If the blade encounters unusually high resistance (a very hard piece of reinforced concrete), pressure rises and the relief valve in the Pressure Relief Valve opens at 280–320 bar, preventing stall.

Cuts of structural steel members are clean and burr-free when the blades are sharp and properly aligned. The Blade Backing Plate reinforces each blade and prevents bending during extreme loading. The Blade Guide Bushing units ensure the moving blade slides smoothly without binding or tilting. Over time, blade edges dull from repeated cutting. Field maintenance involves re-grinding the cutting edge bevel using a portable grinding stone, or in cases of severe chipping, removing the entire Cutting Edge Backing Strip and Fixed Blade Cutting Edge insert and replacing it with a fresh assembly.

The 360° Rotation Motor & Gearing is a separate hydraulic system. A Rotator Motor, powered by continuous excavator pump flow, reduces speed through Rotator Gearing to 8–15 rpm. This drives a Rotator Output Shaft emerging from the Coupler Attachment Boss. As the operator rotates the attachment, the jaw plane changes orientation, allowing efficient approach to different structural members without excavator repositioning.

Connection to the excavator is through the Hydraulic Coupler & Hose Set. Four quick-disconnect flat-face Quick-Disconnect Coupler couplers are typical: two for shear blade pressure and return, two for rotation. The Shear Pressure Hose brings high-pressure flow to the cylinder; the Shear Return Hose exhausts low-pressure flow back to the excavator reservoir. The Rotation Hose powers the rotation motor continuously. A Pressure Gauge on the shear circuit lets the operator monitor load; sudden pressure spikes indicate a hard material or a stuck cut requiring operator adjustment.

The Main Frame & Structure is a robust ductile-iron or welded-steel structure. The Side Plate members are thick enough to resist the side-load shear forces trying to bend the frame apart. The Blade Pivot Axle and its bushings must be oversized to prevent play; loose pivot alignment ruins blade-to-blade contact and results in poor cuts or chatter.

Demolition shears are used extensively in structural steel dismantling, where clean cuts minimize dust and allow rapid extraction of member segments for recycling. They are also used to section reinforced concrete beams and columns during surgical demolition, where precision and minimal collateral damage are priorities. A skilled operator can maintain a rhythm of cutting multiple pieces per minute, making the shear one of the highest-productivity demolition tools available for structural work.