Steel Parallels

BS 906:1972 | Quality Steel | UKAS Certified

Eley’s steel parallels are precision-ground, hardened steel blocks supplied in matched pairs, with multiple working faces for accurate setup. UKAS accredited to BS 906:1972 means they are supplied with four working faces and calibrated for instant workshop or inspection use.

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  • Machine shops where workpieces need to be raised, supported and aligned accurately while maintaining clear access for cutting tools during machining operations.

  • Toolrooms where reliable, repeatable support is important for setting up components, checking height and achieving consistent positioning.

  • Inspection and layout departments where parallels help provide a stable, accurate reference for measuring, marking out and verifying components.

  • Milling and grinding operations where maintaining clearance for cutting tools and supporting the workpiece evenly is essential for accuracy and finish quality.

  • General precision engineering applications where a repeatable setup is needed to improve stability, alignment and confidence in measurement or machining tasks.

Steel Parallels to BS 906 (1972) Standard Sizes & Overall Flatness

GRADE
SIZE (mm)
SQUARENESS (µm)
PARALLELISM (µm)
A
200 x 40 x 20
5
6
A
250 x 50 x 25
10
10
A
300 x 60 x 30
10
10
A
400 x 100 x 50
15
12
B
200 x 40 x 20
10
12
B
250 x 50 x 25
20
20
B
300 x 60 x 30
20
20
B
400 x 100 x 50
30
25

Related Measurement Solutions

Digital Height Gauges

Use digital height gauges with parallels for fast comparative measurements across multiple parts.

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Granite Surface Plates

Place steel parallels on granite surface plates to support parts at consistent heights during measurement.

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Industries Used In - Steel Parallels -

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

Precision Engineering

Supporting precision components at controlled heights and providing parallel reference faces for milling, drilling and grinding operations.


Precision engineering companies use steel parallels in pairs to ensure workpieces sit level and parallel to the machine table, improving accuracy for close‑tolerance machining and inspection.

A manual machinist with safety glasses and an apron adjusting components on a blue industrial lathe machine in a machine shop.

Machine Shops & Toolrooms

Raising workpieces above the vice jaws or machine table, creating clearance for through‑holes, and maintaining parallelism during general machining.


Machine shops and toolrooms rely on steel parallels as everyday setup tools for conventional and CNC machines, giving stable, repeatable support under a wide range of part sizes.

A quality control inspector looking through a specialized optical comparator or measuring microscope to check a precision machined part.

Metrology & Quality Inspection

Supporting parts on surface plates and in vices for dimensional checks, height measurements and verification of parallel faces.


Metrology and inspection teams use ground steel parallels where a robust, wear‑resistant support is needed to keep components level for gauge, indicator and CMM measurements.

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

Automotive Manufacturing

Positioning engine blocks, housings, brackets and precision components at known heights and in parallel alignment for machining and inspection.


Automotive manufacturers use steel parallels extensively in production vices and fixtures to ensure consistent, repeatable setups for drilling, boring, milling and quality checks.

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

Tool and Die Manufacturing

Supporting die blocks, mould inserts, punches and tooling components in vices and on surface grinders for accurate machining and finishing.


Tool and die makers use steel parallels to maintain parallelism and uniform support when grinding faces, machining slots or finishing critical mould and die surfaces.

FAQs

How often do steel parallels need to be calibrated?

Calibration frequency depends on usage intensity and your QMS requirements.

 

In production machining environments, steel parallels are often subject to an annual dimensional verification covering height uniformity, flatness and parallelism of working faces using a surface plate and electronic height gauge. In regulated inspection environments, more frequent calibration (6–12 months) is typical. Any parallel that shows visible wear, damage, surface corrosion or produces inconsistent readings against a trusted reference should be removed from service and checked before further use.

Contact us for scheduled calibration and maintenance of your steel parallels.
Email: sales@eleymet.com
Phone: 01332 367475

Grade A steel parallels are manufactured to tighter flatness and parallelism tolerances and are intended for close-tolerance work including precision inspection, surface grinding setups and toolroom applications where measurement integrity is critical.

Grade B carries slightly wider tolerances and is suited to general machining operations, levelling work in milling and drilling setups, and applications where high-precision parallelism is not a primary requirement. Eley steel parallels are manufactured to BS 906 Parts 1 & 2 in both metric and imperial, hardened to approximately 64 HRc, stress-relieved and stabilised to maintain accuracy over long service life.

Steel parallels are typically selected by height and length to suit the workpiece dimensions and the machine or vice being used.

 

Parallels are commonly available in sets covering a range of heights — typically from around 6 mm up to 50 mm in standard increments — allowing the correct height to be selected for the clearance required beneath the workpiece.

 

For milling and grinding setups, choose a height that raises the workpiece sufficiently above the vice jaws for the cutting tool or grinding wheel to pass over, while keeping the workpiece as low as possible for stability.

 

For inspection use on a surface plate, height selection is driven by the clearance required to access datum features. Parallels can also be stacked to achieve intermediate heights not available as a single piece.

Steel parallels are the standard choice for machine-tool environments as they are lightweight, compact, and well-suited to milling, grinding and drilling setups where magnetic chucks may be in use and where the parallels need to be moved and repositioned quickly.

 

Granite parallels offer superior thermal stability (lower coefficient of thermal expansion), are non-magnetic and rust-free, making them the preferred choice for inspection laboratories, CMM setups and coolant-rich environments where rust or magnetism would compromise measurement integrity or component condition.

 

For purely metrology-focused work, granite parallels are generally the more stable long-term reference; for machine-tool workholding and general shop use, steel parallels are the practical workhorse choice.

Yes. Steel parallels are supplied in matched pairs, with both parallels in the pair ground to the same height within the tolerance of their stated grade.

 

This ensures that a workpiece resting across both parallels sits on a true, consistent reference plane without rocking, a critical requirement both in machining setups (to prevent the vice from introducing a taper) and in inspection work (to maintain the datum integrity of the support surface).

Steel parallels require simple but consistent care to maintain their accuracy and surface condition:

 

  • Cleaning: Wipe all ground faces clean before and after each use with a soft, lint-free cloth. Remove swarf, abrasive particles and coolant promptly. Contamination between the parallel and the workpiece or vice jaw introduces height error and can damage working faces.
  • Corrosion prevention: Apply a light film of rust-preventative oil to all faces when not in use, particularly in environments where coolant or moisture is present.
  • Burr inspection: Check faces regularly for nicks and burrs from accidental contact with cutters or clamping hardware. Minor burrs can be carefully removed with a fine stone; heavily damaged parallels should be set aside for regrinding or replacement.
  • Storage: Store in matched pairs in a clean, dry drawer or case, ideally labelled by size. Keep them separated from loose tooling that could impact and damage the ground faces.

Eley steel parallels within the metrology tooling range can be supplied with either an Eley Metrology certificate of calibration or a UKAS traceable calibration certificate, confirming height, flatness and parallelism values for both pieces in the pair against BS 906 tolerances.

 

This provides the documented evidence required for QMS frameworks. Many general-purpose parallels are supplied with a manufacturer’s inspection report only, for regulated industries, UKAS-traceable calibration should be specified.