ISO 5456-3:1996

Overview

ISO 5456-3:1996 - "Technical drawings - Projection methods - Part 3: Axonometric representations" defines recommended rules and conventions for axonometric (parallel) pictorial projections used in technical drawings. It explains the geometric basis (parallel projection from an infinitely distant point onto a single projection plane), prescribes how to position coordinate axes and the object, and identifies a small set of axonometric types suitable for engineering, electrical, construction and related technical documentation.

Key topics and technical requirements

• Projection principle: Axonometric representations are parallel projections from an infinitely distant projection centre onto the drawing plane (suitable approximation for distant views).
• Coordinate system: Choose axes so the Z‑axis is vertical; projected axes on the drawing plane are labeled X, Y, Z (use uppercase for axes and lowercase x, y, z when mixing with other labels).
• Object orientation: Orient principal faces, axes and edges parallel to coordinate planes so the principal view corresponds to the orthogonal projection.
• Recommended axonometries:
  • Isometric - projection plane forms equal angles with X, Y, Z; projected unit lengths equal and commonly drawn on an equilateral-triangle grid. Projected unit length ≈ sqrt(2/3) ≈ 0.816; equivalent enlargement factor ≈ sqrt(3/2) ≈ 1.225 when representing with unit lengths of 1 on the drawing.
  • Dimetric - used when one view is of primary importance; projected scale ratios typically ux':uy':uz' = 1/2 : 1 : 1 (per example in the standard).
  • Oblique - projection plane parallel to one coordinate plane; includes:
    • Cavalier - third axis projected at 45° with same scale on all axes.
    • Cabinet - similar to cavalier but third axis scaled by 1/2 to reduce distortion.
    • Planometric - projection plane parallel to horizontal plane; variants include normal (scales 1:1:1) and shortened (scales 1:1:2/3).
• Drawing conventions:
  • Hidden contours and edges are normally omitted.
  • Axes of symmetry not drawn unless needed.
  • Hatching for sections is preferably at 45° relative to axes/contours, with hatching for planes parallel to coordinate planes drawn parallel to the projected axis.
  • Dimensioning: Generally avoided on axonometric views; if needed, follow ISO 129 and ISO 3098-1 rules.

Applications and practical value

• Use ISO 5456-3 for consistent pictorial representations in:
  • Mechanical part and assembly illustrations
  • Technical manuals and product documentation
  • Architectural and construction sketches
  • Town planning and map-like views (planometric axonometry)
  • Technical illustrations where a clear, measurable pictorial view is required
• Benefits include predictable visual proportions, standardized scales and axis placement that improve readability, interoperability, and CAD/BIM output consistency.

Who should use this standard

• Drafters, CAD technicians, technical illustrators, mechanical and civil engineers, architects, documentation specialists, and standards authors preparing or checking technical drawings and product documentation.

Related standards

• ISO 5456‑1 (Synopsis), ISO 128 (presentation principles), ISO 129 (dimensioning), ISO 3098‑1 (lettering), ISO 10209 (terms), and informative reference ISO 6412‑2 (isometric pipeline representation).