Fitting piece

A fitting piece is a precisely manufactured intermediate or spacer component used in demolition, cutting, and drilling applications to compensate dimensions, center components, transfer loads cleanly, or make interfaces compatible. In conjunction with Darda GmbH hydraulic attachments and handheld tools – such as concrete demolition shears, rock and concrete splitters, combination shears, or steel shears – fitting pieces ensure a precise fit, improve process stability, and support a reproducible, safe way of working on the construction site, in rock, and in tunnels. By minimizing tolerance stack-ups and defining bearing faces, they contribute to consistent results and reduced rework under tough site conditions.

Definition: What is meant by a fitting piece?

A fitting piece is a dimensionally accurate, often ground component used as an adapter, compensation or spacer between two parts. It performs functions such as centering, aligning, spacing, reducing or increasing connection dimensions, or defining a support and load-transfer surface. Fitting pieces can be installed permanently or temporarily, are usually made of steel or aluminum, and are used at mounting points, in bearings, hydraulic connections, tool interfaces, and borehole environments. In practice, common forms include shims, adapter plates, and centering sleeves that help achieve repeatable assembly conditions.

Function and application scope of fitting pieces

In practice, fitting pieces perform several tasks: they compensate for manufacturing and installation tolerances, protect adjacent components, ensure the correct installation position, and provide defined load transfer. In concrete demolition and special deconstruction as well as in rock excavation and tunnel construction, they help position Darda GmbH tools safely – for example, when applying a concrete demolition shear to load-bearing members or inserting a rock and concrete splitting cylinder into a borehole. They are also used in strip-out and cutting to set cutting gaps, jaw or blade clearances, and to adapt to varying material thicknesses.

• Process stability: reproducible clearances and positions lower the risk of jamming, miscuts, or uncontrolled fractures.
• Component protection: defined contact prevents notch effects and edge spalling on concrete and steel.
• Efficiency: shorter setup times and fewer corrective cuts due to standardized interfaces.

Designs and materials

Fitting pieces differ by design, material, and tolerance class. Selection depends on function, load, and environmental conditions. Depending on the task, accuracy ranges from ground shims with tight thickness tolerances to robust adapter plates with defined flatness and parallelism. Where precise guidance is required, fits based on common ISO systems and finely finished surfaces improve alignment and minimize wear.

Typical designs

• Spacer rings and shims for height or thickness correction
• Adapter plates and intermediate plates to adapt mountings
• Centering bushings and sleeves for precise alignment
• Reducers or expanders for connection diameters on hydraulic lines
• Support and protection plates to protect concrete edges and borehole mouths
• Wear shims in jaw guides to set side play and maintain blade tracking
• Tapered or profiled liners for angular correction where faces are not parallel

Materials and surfaces

• Quenched and tempered steel for high compressive and impact loads
• Tempered or hardened shims for wear-intensive bearing points
• Aluminum or stainless steel where weight, corrosion protection, or media resistance are paramount
• Surface treatments such as bluing, galvanizing, or nitriding to reduce wear and corrosion
• Bronze or brass for sliding interfaces and mixed-material bearings
• Coatings with high hardness and low friction to stabilize clearances under load

Fitting pieces in conjunction with rock and concrete splitters

When splitting concrete or natural stone, boreholes with defined diameter and depth are produced. Here, fitting pieces can serve as centering sleeves or protection rings to guide the splitter cylinder precisely in the borehole and protect the borehole mouth from spalling. Spacer shims make it possible to compensate for small deviations in borehole depth so that the wedge of the splitting cylinder operates in the optimal position. This improves splitting performance, reduces edge chipping, and lowers stress on both tool and material.

For demanding substrates, reinforced protection rings with chamfered edges reduce local stress peaks. Selecting suitable wall thicknesses for sleeves improves guidance without increasing insertion force excessively, while debris relief grooves help keep the borehole mouth clean during repeated insertions.

Fitting pieces on concrete demolition shears, combination shears and Multi Cutters

On gripping and cutting tools, fitting pieces ensure the correct geometry: shims on pivot bolts set the defined jaw or blade clearance; intermediate plates on mountings adapt the tool to carrier machines or handling systems. A cleanly adjusted cutting or gripping gap reduces wear on blades and jaws, improves cut quality, and supports an even load distribution over the entire stroke.

In addition, parallel closing of jaws can be maintained over the service life by staged shim packs. Defined lateral guidance minimizes backlash, enhances cut entry, and lowers the risk of skewed load paths in the frame structure.

Hydraulic fitting pieces: adapters and transitions

In hydraulic systems, fitting pieces connect different connection geometries, threads, or nominal sizes. Decisive factors are permissible operating pressure, sealing type, and media compatibility. Adapters and reducers must match the pressure rating of the hydraulic power pack and the connected tools to avoid pressure losses and leaks. Important is a clean, stress-free installation: sealing surfaces must not be damaged, and approved sealing compounds must be used and applied in the correct quantity.

• Typical sealing concepts: metal cone seats, O-ring face seals, bonded seals with parallel threads, and tapered threads with compatible sealants.
• Thread integrity: correct engagement length and torque prevent microleaks and thread galling.
• Flow layout: avoid abrupt cross-section changes and sharp bends that cause pressure drops and heating.

Selection criteria and design

The design of a fitting piece is guided by mechanical, geometric, and operational requirements. The goal is safe, repeatable function without impermissible deformation or play.

Relevant criteria

• Function: centering, spacing, adapter function, protection
• Load case: compressive, shear, bending, and impact loads
• Dimensions and tolerances: fit, flatness, parallelism
• Material and heat treatment with regard to strength and wear
• Environment: moisture, corrosion, temperature, dirt
• Hydraulics: pressure rating, sealing concept, compatible media
• Surface finish and edge radii in load introduction zones
• Serviceability: accessibility for inspection, clear identification and stackability

Installation and practice

Proper installation ensures full effectiveness of the fitting piece and protects adjacent components.

1. Clean components; remove burrs and damage on support or sealing surfaces.
2. Check dimensions (thickness, runout, fit). Observe identification and installation orientation.
3. Insert the fitting piece without stress; ensure full-surface contact of the bearing faces.
4. Tighten fasteners to the specified torque; re-tighten screws or bolts if necessary.
5. Perform a functional test (stroke, gripping or cutting clearance, leakage test in the hydraulics).
6. Update documentation (thickness, position, date) to keep later settings reproducible.

Lubrication, friction coefficients, and tightening sequences influence the achieved preload. Where several shims are stacked, alternate orientations and deburr edges to avoid measurement errors and settling.

Safety and diligence

Fitting pieces affect load transfer and thus operational safety. Installation and use should follow the applicable technical rules. Stated permissible loads, torques, and pressure ratings must be observed. Changes to tool geometries, mountings, or hydraulic connections should be professionally assessed and documented. Legal requirements may vary by country and must be observed for the specific application.

Before commissioning, conduct a risk assessment for the specific setup, including pinch points at jaws, potential ejection of parts, and hydraulic overpressure risks. Protective measures and lockout procedures reduce residual hazards.

Maintenance, wear, and replacement

Fitting pieces are wear parts, especially when they act as support or spacing surfaces within the load path. Regular visual and dimensional inspections (loss of thickness, plastic deformation, notches, corrosion) are advisable. Heavily loaded shims or protection rings should be replaced in good time to prevent consequential damage to tools or components. In hydraulic systems, sealing surfaces and threads must be checked each time connections are separated or made.

Document measured values with feeler gauges or micrometers and compare over time to identify trends. Replace stacked shim packs as a set if the original configuration can no longer maintain the specified clearance.

Common mistakes and how to avoid them

• Incorrect thickness or fit: leads to stresses and uneven load distribution.
• Inappropriate material: insufficient strength or corrosion resistance.
• Damaged support or sealing surfaces: promote play, settling effects, or leaks.
• Unclear documentation: makes reproducible settings on concrete demolition shears or splitting cylinders difficult.
• Incompatible hydraulic adapters: risk of pressure losses and seal failure.
• Mixing thread standards or sealing concepts: increases leak probability and assembly damage.
• Makeshift shims from soft or unapproved materials: accelerate wear and compromise geometry.

Application examples in the fields of use

Concrete demolition and special deconstruction

Fitting pieces define gripping and cutting geometries on concrete demolition shears, secure adapter plates on mountings, and protect concrete edges during positioning. Spacer rings compensate tolerances so jaws close in parallel and the cut runs true. This ensures consistent cut entry and reduces blade dressing intervals.

Strip-out and cutting

With varying component thicknesses, shims enable repeatable settings. Intermediate plates support precise positioning of combination shears or Multi Cutters on handling systems. Predefined shim stages allow fast changeovers between material classes.

Rock excavation and tunnel construction

Centering sleeves guide splitting cylinders in the borehole, minimize edge spalling, and improve directional accuracy during splitting. Protection rings at the borehole mouth prevent damage at the exit zone. In fractured rock, reinforced sleeves stabilize guidance and reduce kickback tendencies.

Natural stone extraction

Fitting pieces provide defined bearing on uneven rock surfaces and support a straight split pattern through precise cylinder guidance. Robust protection plates also help preserve visible edges for subsequent processing.

Special applications

For atypical geometries or limited installation space, special fitting pieces are used – for example, particularly flat spacer plates or profiled protection pieces that deliberately redirect forces and protect adjacent surfaces. Where thermal effects are relevant, differential material selection limits distortion.

Quality assurance and traceability

Marking fitting pieces (thickness, material, batch) facilitates traceability and spare parts management. Inspection records of dimensions and surface condition as well as photos of the installation situation support consistent use over the service life of Darda GmbH tools.

• Identification: durable engraving or stamping of thickness and material.
• Documentation: storage of inspection data linked to tool and position.
• Storage: protected, dry, and sorted by thickness to prevent mix-ups.