Tool bits are the decisive interface between power unit and material in demolition, deconstruction and natural stone extraction. Whether concrete demolition shears, stone and concrete splitters, combination shears or tank cutters: Only suitable and well-maintained tool bits—chisels, wedge sets, knives or jaw inserts—enable controlled force transmission, precise separation cuts and reproducible splitting results. This article classifies the term technically, explains designs, selection criteria and maintenance, and relates it to attachments and hydraulic solutions from Darda GmbH—objective, practice-oriented and free of promotional language.
Definition: What is meant by tool bits
Tool bits are interchangeable, positively locked working tools that are inserted into a mount (shank, jaw, wedge seat or clamping) of a carrier machine or handheld tool. They transmit energy—hydraulic, pneumatic or mechanical—into a work action suitable for the respective material: cutting, breaking, splitting, chiseling. In the context of Darda GmbH, the term includes in particular wedge sets for stone and concrete splitters, cutting and breaker bars as well as knives and teeth for concrete demolition shears, combination shears, Multi Cutters, steel shears and tank cutters. The correct choice and condition of these wear parts significantly determine the performance, quality and operational safety of the entire system.
Design, geometry and materials of tool bits
Tool bits follow a clear functional logic: secure force transmission at the interface, optimal shape at the working end, tough core strength and wear-resistant surface. Depending on the task and device, cross-sections, lengths and heat treatments vary.
Typical components
- Mount/Shank: Mating surfaces, guides, holes or supports for bolt or screw connections; within tolerance for a precise, play-free fit.
- Transition zone: Geometrically reinforced to limit notch stresses; often with soft radii.
- Working end: Executed as a point, chisel edge, wedge face, knife or tooth depending on function; optimized for wear resistance and fracture toughness.
- Surface: Blasting, induction surface hardening or coating to improve service life and corrosion protection—always within the scope of the manufacturer’s approvals.
Materials and heat treatment
Proven choices are alloyed tool and fine-grain steels with a tough base hardness and a locally adapted surface layer. The goal is a balanced combination of wear resistance and impact toughness. Overheating during grinding or improper hardfacing can destroy this balance; therefore use only approved procedures.
Types in demolition, deconstruction and extraction
Tool bits differ by working principle, material contact and type of interface. In the application areas of Darda GmbH, the following are particularly relevant:
- Chisels (pointed, flat, channel chisels): For concrete removal, opening joints and removing shotcrete; selection based on member thickness, reinforcement density and required edge quality.
- Wedge sets/insertion wedges for hydraulic rock and concrete splitters: Center and counter wedges, matched to borehole diameter and cylinder type; for low-vibration concrete demolition, rock excavation, tunnel heading and natural stone extraction.
- Cutting knives, teeth and jaw inserts for concrete demolition shears, combination shears, Multi Cutters, steel shears and tank cutters: Replaceable contact parts for precise separation cuts in concrete, reinforcement, structural steel sections, tanks and pipelines.
- Special geometries: Breaker bars, comb profiles, toothed knives or profiled pressure pieces for special tasks and material-dependent fracture guidance.
Relation to devices and application areas of Darda GmbH
Tool bits are an integral part of equipment application—their specification follows the task:
Concrete demolition shears in concrete demolition and special deconstruction
In concrete demolition shears, breaker teeth, cutting knives and impact faces determine the quality of the separation joint and the behavior on reinforcing steel. For heavily reinforced concrete, robust cutting edges with suitable edge stability are required; during building gutting and cutting, tight radii and clean cut edges are advantageous. Replacing worn inserts maintains the nominal force in the working zone and reduces crushing and tear-off hazards.
Stone and concrete splitters in rock excavation, tunnel construction and natural stone extraction
Wedge sets transmit the hydraulic spreading force of the cylinder into the borehole. Borehole diameter, insertion depth, wedge angle and lubrication influence split direction, split width and surface quality. In brittle rocks, sharply defined wedge faces support controlled crack initiation; in concrete with a heterogeneous aggregate structure, suitable wedge radii promote reproducible crack propagation.
Combination shears, Multi Cutters, steel shears and tank cutters
Replaceable knives and jaw profiles define cutting clearance, penetration behavior and burr formation. For structural steel sections, tailored knife geometries are often selected to avoid crushing and achieve proper shear fracture. During tank cutting, spark and ignition hazards must be considered; dull knives increase local heating—regular replacement supports a cooler, controlled cut.
Selection criteria: Fit, performance and material
The selection of a tool bit follows technical necessities and safety requirements. Key criteria are:
- Mounting interface and dimensions: Suitable shank or jaw seat, permissible lengths and cross-sections; play-free fit to prevent edge loading.
- Device performance class: Hydraulic pressure and flow rate or impact energy; tools must permanently withstand the system forces.
- Material and structure: Concrete strength, reinforcement ratio, rock type (tough, brittle, schistose), temperature range.
- Geometry: Point angle, cutting bevel, wedge angle, serration; influences penetration, crack formation and cut quality.
- Operating environment: Water, mud, dust, corrosive media; determines lubrication, protection and cleaning intervals.
- Boundary conditions: Minimum edge distances when splitting, permissible borehole tolerances, required cutting clearances for shears.
Compatibility and mounting systems
Tool bits are only safe if interface, tolerances and fastening match exactly. The specifications of the respective device apply. Common fastenings are positively locked shank mounts, bolted knife and tooth plates, or inserted wedge sets with a defined seat. Incompatible combinations increase the risk of pull-out, edge chipping and uncontrolled load peaks.
Maintenance, care and change intervals
As wear parts, tool bits require scheduled maintenance. This preserves force transmission, cut quality and occupational safety.
Inspection
- Before use: Visual check for cracks, chipping, plastic deformation and damage to seating surfaces.
- During operation: Observe temperature and noise; unusual vibrations indicate play or misfit.
- After use: Cleaning, drying, light preservation; wear documentation for planning the next change.
Rework and replacement
Cutting edges and bevels may only be reground within specified tolerances. Excessive removal alters the force flow. For hardfacing, the manufacturer’s approval is decisive. If cracks are suspected, take the tool out of service and replace it.
Lubrication and borehole care during splitting
Keep wedge faces clean and, if required, lubricate with suitable agents; de-dust and blow out boreholes. Deposits increase friction and reduce splitting effectiveness.
Safety and compliant operation
Safe application begins with selection and continues through assembly, operation and storage. Personal protective equipment, regular instruction and careful work preparation are mandatory. On hydraulic systems: always relieve pressure in a controlled manner before changing tool bits. Plan for safety distances, catch zones and potential fragment flight directions. Legal and operational requirements are site- and task-specific; binding case-by-case assessments are made by those responsible on site.
Practical guide: 6 steps to the right tool bit
- Analyze the structural element: material, thickness, reinforcement/inserts, edge distances, desired separation or split direction.
- Determine the device: concrete demolition shear, stone and concrete splitter, combination shear, Multi Cutter, steel shear or tank cutter; consider available Hydraulic Power Units.
- Check the interface: fit, fastening, permissible dimensions and tolerances.
- Choose the geometry: wedge angle, knife shape, tooth profile, chisel type; align to cut quality and member behavior.
- Evaluate the environment: moisture, temperature, ignition sources, emissions; if necessary, choose an alternative cutting or splitting strategy.
- Plan maintenance: change and grinding intervals, spare parts availability, documentation.
Typical errors and how to avoid them
- Wrong wedge size in an oversized/undersized borehole: insufficient crack formation or wedge jamming—adhere exactly to the borehole dimension.
- Dull knives in concrete demolition shears: increased force demand, burr formation, heating—replace in time or regrind professionally.
- Play in the interface: edge blows, chipping—inspect seating surfaces, replace wear parts.
- Unsuitable geometry for reinforced concrete: adapt cutting bevel and tooth profile to the reinforcement ratio.
- Dry running without lubrication on wedge sets: increased wear—keep contact surfaces clean and lightly lubricated, if approved.
Sustainability and service life optimization
Targeted tool selection, correct drilling and splitting, timely knife replacement and proper grinding increase tool service life and reduce material consumption. Precise inserts for concrete demolition shears minimize rework, while well-matched wedge sets in stone and concrete splitters enable fractures along planned planes. This lowers energy demand and emissions and improves predictability in concrete demolition, building gutting and cutting, rock excavation and tunnel construction, natural stone extraction as well as special demolition applications.