Granite Straight Edges

UKAS Certified | Hand Lapped | BS 5204:1977

Hand‑finished straight and parallel to BS 5204 Part 2:1977, Eley’s granite straight edges can be produced with either one or two master faces. Customisation options include lightening holes and detachable handles for safer handling of longer sections.

Request quote
Request calibration
  • Standard Straightedges have one master face, offering a cost‑effective yet highly accurate solution for routine inspection and setup.

     

  • Master Straightedges have two master faces, enabling inspection and comparison on opposite faces from a single artefact.

     

  • Parallel on the 1½″ or 2″ face: Both master and standard straight edges provide a robust measuring surface when used on granite surface plates or machine beds.

     

  • Optional lifting holes and detachable handles: improve handling and safety for longer or heavier sections.
  • Checking straightness and alignment of machine tool beds, slideways, guide rails and large components.
  • Inspection of fabricated structures, jigs, fixtures and assemblies
  • General workshop measurement where a stable, non‑wearing reference edge is required

Our master straight edges are produced with two master faces (standard versions have one), and are parallel on the 1 1⁄2″ or 2″ face. Master versions enable higher‑flexibility inspection workflows by allowing comparison on opposite faces without re‑fixturing. 

Granite Straight edges to BS 5204 (1977) Standard Sizes & Overall Flatness

GRADE
SIZE (mm)
SQUARENESS (µ)
WEIGHT (kg)
AA
1000 x 125 x 45
4
20
AA
1500 x 150 x 55
6
37
AA
2000 x 150 x 55
7.5
50
A
1000 x 125 x 45
8
20
A
1500 x 150 x 55
12
37
A
2000 x 150 x 55
15
50

Related Measurement Solutions

Digital Height Gauges

Explore the VMS digital height gauge range to extend your probing work into detailed profile and 1D & 2D feature measurement.

View

Granite surface plates

Combine your height gauge and probes with Eley’s precision granite surface plates for stable, traceable measurements.

View

Industries Used In - Granite Straight Edge -

A technician wearing a yellow hard hat and safety glasses using a calliper to check the precise inner dimensions of a machined metal component.

Machine Tool Manufacturing

Checking machine table straightness, aligning ways and beds, verifying assembly accuracy, and inspecting large machined surfaces for distortion.

 

Granite straight edges are widely used in machine tool manufacturing, calibration, and maintenance to ensure accurate alignment and reliable straightness verification.

A CMM touch-trigger probe conducting a dimensional measurement on a precision machined component secured on a granite surface plate.

Precision Engineering

Inspecting small precision parts, verifying straightness and flatness tolerances, checking machined features, and measuring fine geometries.

 

Granite straight edges are specifically noted for precision engineering applications and high‑precision quality control on the production floor and in metrology labs.

A military fighter jet taxiing on a runway, showcasing precise aerodynamic engineering and defence technology.

Aerospace & Defence

Checking large fabricated parts, machine beds, structural components, and welded assemblies for straightness, wear, or distortion.


In aerospace and defence manufacturing, granite straight edges provide a durable, stable reference for straightness and flatness inspection on large-scale components and equipment.

An automated coordinate measuring machine (CMM) probe performing high-precision dimensional inspection on a manufactured aluminium part.

Metrology & Quality Inspection

Serving as a stable reference for flatness verification, straightness inspection, and geometric accuracy checks on precision components.

Metrology and quality inspection teams use granite straight edges as trusted reference tools for flatness and straightness measurement in precision inspection workflows.

Unfinished car bodies moving along an automated assembly line track inside an automotive manufacturing facility.

Automotive Manufacturing

Inspecting engine blocks, cylinder heads, precision fixtures, jigs, and machining components for straightness, flatness, and alignment accuracy.

 

Granite straight edges are commonly used in automotive manufacturing during tooling build, fixture setup, and quality control of critical machined parts.

FAQs

What is the difference between a straight edge and a master straight edge?

A standard granite straight edge has one precision-lapped narrow face, providing a single flatness and straightness reference.

 

A master straight edge has two narrow faces lapped flat and parallel to one another, giving both a straightness reference and a parallelism reference from the same artefact. This dual-face configuration is preferred in calibration laboratories and for machine tool qualification tasks where both straightness and parallelism must be verified independently and traceably.

Grade AA (Laboratory Grade) is manufactured to the tighter straightness tolerances of BS 5204 Part 2:1977 and is the correct choice for UKAS-accredited laboratories, primary reference standard applications and high-precision optical or semiconductor equipment alignment.

 

Grade A (Inspection Grade) carries slightly wider tolerances and is well-suited to production inspection departments, shop-floor machine verification and on-site installation work. As with all reference standards, a traceability hierarchy should be maintained – using a Grade AA master to periodically verify any Grade A working straight edges.

Yes. Granite straight edges that have moved out of tolerance can be professionally resurfaced and recalibrated rather than replaced.

Eley’s engineers hand-lap the working faces back to BS 5204 Part 2:1977 specification, followed by UKAS traceable re-verification. This is a cost-effective option — particularly for longer master straight edges — and can be performed at our Derby laboratory or, where appropriate, on-site.

Contact us to discuss your requirement today.
Email: sales@eleymet.com
Phone: 01332 367475

Key maintenance practices include:

  • Cleaning: Wipe working faces before and after each use with a lint-free cloth and a specialist stone cleaner or denatured alcohol. Avoid water-based or aggressive solvents.
  • Handling: Always lift a straight edge, never drag it across a surface. Use the lifting holes provided on larger sizes. Avoid placing the straight edge on unclean or uneven surfaces that could cause localised loading.
  • Storage: Store horizontally on a stable, vibration-free surface, covered to prevent dust and particulate contamination. Maintain a consistent, temperature-controlled environment where possible.
  • Inspection: Regularly check working faces for chips, contamination or uneven wear. Any suspected deviation from straightness tolerance should be referred for professional recalibration.
  • During use: Always measure on stationary workpieces at ambient temperature and lift rather than slide the straight edge between measurement positions to protect the lapped face.

Eley offers resurfacing and recalibration services to restore straight edges back to BS 5204 Part 2:1977 specification.

Contact one of our specialists for a calibration quote today.
Email: sales@eleymet.com
Phone: 01332 367475

Yes. All Eley granite straight edges can be supplied with a UKAS traceable calibration certificate from our UKAS-accredited laboratory (No. 30213). The certificate documents the measured straightness deviation across the working face, measurement uncertainty and traceability to national measurement standards, providing the evidence required for QMS frameworks.

As with all precision reference standards, calibration frequency should be based on usage intensity, application criticality and your QMS requirements. For high-cycle production or shop-floor environments, a 6–12 month interval is a practical guide; controlled laboratory use may suit an annual schedule.

 

In regulated sectors such as aerospace or medical device manufacturing, where straightness tolerances are in the low-micrometre range, more frequent calibration is typically specified to prevent measurement drift. Calibration should also be triggered immediately following any impact, suspected damage or unexplained inconsistencies in measurement results.

 

All Eley granite straight edges can be supplied with UKAS traceable calibration and we offer ongoing recalibration to BS 5204 Part 2:1977.

 

Contact us to discuss regular maintenance of your granite artefacts.
Email: sales@eleymet.com
Phone: 01332 367475

Length selection is determined by the span of the surface or axis being inspected, the straight edge should equal or exceed the full length of the feature to ensure end-to-end coverage. Eley granite straight edges are available in standard lengths of 1000 mm, 1500 mm and 2000 mm, with straightness tolerances from 4 µm (Grade AA, 1000 mm) to 15 µm (Grade A, 2000 mm) per BS 5204 Part 2:1977.

 

For machine tool and CMM installation work on larger vertical machining centres or grinding machines, 1500–2000 mm straight edges are typically specified. For bench-level inspection and shorter axis checks, 1000 mm is the most common selection. Bespoke lengths and cross-sections are available for specialist applications.

 

Reach out to us to discuss your bespoke requirements.
Email: sales@eleymet.com
Phone: 01332 367475