Long Bore CMM, Long Reach CMM

2 - 3 Metre Lance | British Manufactured | 0.5 Micron Resolution

Measuring precision parts like no other machine can, the Long Bore Measurement (LBM) CMM is a groundbreaking solution to one of the most challenging areas in metrology: achieving precision measurement deep inside long, narrow bores.

Developed by Eley Metrology, it enables accurate inspection of tubular components such as jet engine shafts, undercarriage parts to nuclear/small modular reactor components, where internal geometry is critical to performance and safety.

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Overview

Dedicated solution for deep bore metrology:
The Long Bore CMM is specifically engineered to measure features located deep within tubular and hollow components, where conventional CMMs and traditional gauging methods struggle to provide reliable, traceable results.

By combining a precision guidance system with specialist long-bore probing and advanced analysis software, the LBM offers a dedicated platform for internal diameter, concentricity and form measurement along extended bore lengths.
Precision guidance with dual Z spindle stability:
At the heart of the system is a vee-flat guidance configuration that employs pre-loaded, patented air bearings to ensure smooth, stable motion over the full measurement range.
The machine is equipped with two Z spindles, known as Primary and Secondary, arranged in a parallelogram to provide essential stability to the Z axis and maintain alignment during long-reach measurements.

This construction allows the LBM to deliver volumetric performance at the end of a lance of up to 3.0 metres, with specification derived from manufacturing excellence rather than software correction.
Access to features in small-diameter bores:
The smallest diameter lance can pass through bores as small as 20 mm to reach internal features, allowing inspection at depths that would otherwise be inaccessible.
The LBM can also measure from beneath the Primary Z spindle, offering conventional CMM measurement using the same datum as the touch probe mounted at the end of the main lance, so internal and external features can be measured in a single system and referenced to a common centreline or datum scheme.
Non error-mapped performance with UKAS support:
The machine does not employ error mapping or computer-based correction; instead, its volumetric specification is achieved through precision manufacture of the main guides and structural elements. The X-axis guide is specified to seven microns total, including straightness and parallelism, while the Y and Z axes are maintained within two microns.
Performance is supported by UKAS calibration, reinforcing confidence in the LBM’s ability to deliver traceable, high-accuracy long bore measurements.

Capabilities

Concentricity and internal–external bore alignment:
The Long Bore CMM provides unique performance in applications where the geometry of internal features is critical and must be related accurately to outer diameters or component centrelines.

It is particularly effective for evaluating concentricity between inner and outer diameters, ensuring that internal bores and external bearing surfaces remain aligned within tight tolerances along the length of a component.
Form, PCD and fillet radii evaluation:
In addition to concentricity, the LBM supports circularity and cylindricity measurements, allowing users to assess how closely internal bores conform to ideal roundness and cylinder form.

Pitch circle diameters (PCDs), fillet radii between diameters and partial arcs can also be measured, enabling a comprehensive assessment of internal geometry where only limited access points exist. Straightness and parallelism of the component centreline datum can be verified, supporting critical alignment checks in long rotating shafts and tubular structures.
Reducing uncertainty versus traditional gauging:
Historically, these types of measurements have relied on composite methods using dial indicators and custom gauging, often resulting in large uncertainty budgets that could approach or exceed the available tolerance band.

The LBM was conceived to address exactly this challenge, providing a controlled, traceable method for long-bore metrology that aligns with modern manufacturing capabilities and the increasing demands of designers for higher precision and certainty.
High-resolution measurement and TM5 analysis software:
The system resolves to 0.5 microns, with volumetric measurement capability of better than 40 microns at the end of a 3.0 m lance. Analysis is supported by Eley’s True Measure 5 (TM5) software, which provides both metric and direct inch conversion, simplifying interpretation and reporting across different standards.

Calibration is carried out using traceable master ring gauges mounted in fixtures that replicate real-world tubular measurement problems, validating the system’s ability to report internal and external diameters, concentricities and section-by-section geometric relationships.
Custom-built systems with full aftercare support:
Custom sizes are available on enquiry, allowing the Long Bore CMM to be tailored to specific component lengths, diameters or application needs. As standard, the machine is supported by Eley Metrology’s after-sales and support team, helping ensure that performance is maintained throughout its operational life.

Applications

Precision measurement of long, deep bores where internal features must be quantified and related to external geometry.
Aerospace components such as main engine shafts, where concentricity of inner and outer bearing diameters, blend radii and centreline alignment are critical at operating speeds of up to 20,000 rpm.
Hydraulically operated landing gear and undercarriage components requiring accurate internal diameter, concentricity and form verification.
Nuclear and small modular reactor items and power generation components where internal geometry influences flow, structural integrity or safety performance.
Oil and gas industry components including tubular products, downhole tools and pressure-containing parts requiring internal bore analysis.
Defence systems components and line-bored bearing housings where the relationship between internal bearing surfaces and external reference features is vital.
Any application where precise, traceable measurement of features inside long, deep bores is required, and where traditional gauging methods do not provide sufficient certainty or repeatability.