Engineers Squares

About Engineers Squares

Engineers squares, also known as precision squares or machinist squares, are essential measuring and marking tools designed to provide perfectly accurate 90-degree angles for precision engineering, metalwork, and woodworking tasks. These indispensable tools feature an L-shaped design with a stock (or beam) and a blade set at an exact right angle, allowing tradespeople to check the squareness of workpieces, mark perpendicular lines, and verify the accuracy of machine setups with confidence.

Available in various sizes ranging from compact 50mm models for detailed work to larger 300mm versions for sizeable projects, engineers squares are manufactured to exacting standards using hardened stainless steel or precision-ground carbon steel. The finest examples offer accuracy to within 0.02mm per 100mm, making them invaluable for applications where dimensional precision is critical. Whether supplied individually or as part of a comprehensive set, these tools represent a fundamental component of any professional engineer's or machinist's toolkit.

Our range features trusted brands including Draper, Facom, Faithfull, and Sealey, offering both individual squares and multi-piece sets to suit various precision requirements and budgets. From workshop calibration tasks to on-site fabrication work, a quality engineers square ensures your measurements remain true and your work meets the exacting standards demanded by modern engineering and manufacturing.

Jargon Buster

• DIN 875 Standard: The European standard specification for engineers squares, defining tolerances and accuracy grades (typically Grade 0, 1, or 2, with Grade 0 being the most precise).
• Flatness Tolerance: The maximum deviation from a perfectly flat surface on the square's faces, critical for ensuring accurate measurements and typically measured in microns.
• Squareness Tolerance: The permissible deviation from a perfect 90-degree angle, usually expressed as millimetres per length (e.g., 0.02mm per 100mm), with lower values indicating greater precision.
• Hardened Steel: Heat-treated steel that has been hardened to resist wear, deformation, and damage, ensuring the square maintains its accuracy over prolonged use in demanding workshop environments.
• Flanged Base: A wider, reinforced base on some precision squares that provides additional stability when checking workpieces and prevents rocking on uneven surfaces.
• Ground Edges: Precision-machined edges that have been surface-ground to achieve exceptional flatness and straightness, essential for accurate scribing and measurement verification.

Who Uses Engineers Squares?

Engineers squares are indispensable tools across numerous trades and applications:

• Mechanical Engineers – checking component squareness, verifying machine tool setups, and ensuring dimensional accuracy in manufactured parts
• Toolmakers and Die Makers – precision work requiring absolute accuracy when creating moulds, dies, and tooling components
• Machinists – setting up lathes, milling machines, and grinders, plus verifying workpiece orientation and alignment
• Fabricators and Welders – ensuring steel structures, frames, and assemblies are perfectly square before welding
• Maintenance Fitters – diagnosing machinery problems, checking equipment alignment, and conducting quality control inspections
• Precision Woodworkers – marking accurate cuts, checking joinery, and setting up machinery for fine furniture making
• Quality Control Inspectors – verifying manufactured components meet dimensional specifications and tolerances
• Apprentices and Students – learning fundamental measurement techniques in engineering and manufacturing education programmes
• Serious DIY Enthusiasts – home workshop projects requiring professional-level accuracy and precision

How to Choose the Right Engineers Squares

Selecting the appropriate engineers square depends on several key factors:

Size and Application: Consider the typical dimensions of your workpieces. Smaller 50-100mm squares suit intricate work, model making, and tight spaces, whilst 150-300mm models are better for larger fabrication and general engineering tasks. Multi-piece sets offer versatility for varying applications.

Accuracy Grade: Professional toolmakers and inspectors require DIN 875 Grade 0 or 1 squares with tolerances of 0.01-0.02mm per 100mm. General engineering and fabrication work is well-served by Grade 2 squares, whilst workshop and DIY applications can use standard accuracy models.

Material and Construction: Hardened stainless steel offers excellent corrosion resistance and longevity, ideal for environments exposed to coolants and cutting fluids. Carbon steel squares, whilst requiring more care to prevent rust, often provide exceptional rigidity and wear resistance. Look for precision-ground edges and faces for optimal accuracy.

Base Design: Flanged or reinforced bases provide superior stability when checking vertical surfaces and are less prone to rocking on slightly uneven workpieces. Standard bases are perfectly adequate for most general applications and drawing work.

Brand Quality: Established manufacturers like Facom, Draper, Sealey, and Faithfull maintain strict quality control and offer calibration certificates with their precision models. Investing in reputable brands ensures long-term accuracy and reliability.

Set vs Individual: Four-piece precision square sets provide multiple sizes for different tasks and excellent value, whilst individual squares allow you to select specific sizes for specialised requirements.

Popular Accessories

• Centre Finders and Edge Finders: Complementary precision tools for locating exact centres and edges on workpieces and machine tables
• Engineer's Scribers: Hardened steel marking tools for scribing accurate lines against the square's edge on metal surfaces
• Engineer's Marking Blue: Layout fluid applied to metal surfaces to make scribed lines more visible and permanent
• Precision Spirit Levels: For checking both squareness and level simultaneously during setup and installation work
• Combination Squares: Versatile measuring tools that work alongside engineers squares for marking 45-degree angles and measuring depths
• Inspection Gauge Blocks: Calibrated reference standards for verifying the accuracy of your measuring equipment
• Protective Cases: Padded storage solutions to protect precision squares from impact damage and corrosion during transport
• Workshop Granite Surface Plates: Precision reference surfaces for accurate layout work and measurement verification

Safety Information

Whilst engineers squares don't present significant safety hazards, proper care ensures both personal safety and tool longevity:

Sharp Edges: Precision-ground edges can be extremely sharp, particularly on new squares. Handle with care to avoid cuts, especially when cleaning or inspecting the tool. Consider wearing work gloves when handling multiple squares simultaneously.

Secure Storage: Always store engineers squares in protective cases or dedicated tool drawers to prevent damage from being dropped or knocked. A damaged square cannot be reliably repaired and will compromise measurement accuracy.

Workshop Hazards: Be aware of your surroundings when using squares near rotating machinery. Ensure the square cannot be drawn into chucks, spindles, or other moving parts, which could cause injury or damage equipment.

Regular Calibration: For critical precision work, periodically verify your squares against certified reference standards or granite surface plates, particularly if dropped or subjected to impact. HSE guidelines recommend regular calibration of precision measuring equipment in quality-critical manufacturing environments.

Frequently Asked Questions

What's the difference between an engineers square and a try square?

Engineers squares are manufactured to much tighter tolerances (typically within 0.02mm per 100mm) using hardened steel construction, making them suitable for precision engineering and metalwork. Try squares are woodworking tools with lower accuracy standards, usually featuring wooden or plastic stocks, and aren't appropriate for precision engineering applications requiring dimensional accuracy.

How do I check if my engineers square is still accurate?

Place the square against a known straight edge (such as a precision granite surface plate or recently surface-ground workpiece) and scribe a line. Flip the square over and align it with the same line from the opposite direction. If the square's edge perfectly matches your original line from both orientations, it's accurate. Any visible gap indicates the square is out of true and should be replaced, as engineers squares cannot be reliably adjusted or repaired.

Do I need a set of engineers squares or just one size?

This depends on your typical work. If you regularly work with varying component sizes, a 4-piece set from brands like Faithfull or Sealey offers excellent value and versatility. For specialised work with consistent dimensions, a single appropriately-sized square suffices. Many tradespeople start with a 150mm square for general use, then add other sizes as specific requirements arise.

How should I maintain my engineers square?

After each use, wipe the square clean with a lint-free cloth to remove metal filings, coolant, and debris. Apply a light coating of corrosion-preventive oil if the square is carbon steel rather than stainless steel. Store in a protective case or dedicated drawer location where it won't be dropped or knocked against other tools. Never use engineers squares as prying tools, hammers, or for any purpose other than measuring and marking, as this will compromise their accuracy.

What accuracy grade do I need for general fabrication work?

For most fabrication, welding, and general engineering applications, DIN 875 Grade 2 squares provide more than adequate accuracy. Toolmaking, inspection work, and precision manufacturing require Grade 0 or 1 squares. If you're uncertain, Grade 1 represents an excellent middle ground offering high precision without the premium cost of laboratory-grade Grade 0 tools.