ISO 3098-5:1997

Overview

ISO 3098-5:1997 - "Technical product documentation - Lettering - Part 5: CAD lettering of the Latin alphabet, numerals and marks" specifies general requirements and conventions for computer‑aided design and draughting (CADD) lettering used in technical product documentation. It defines CAD lettering types, spacing arrangements, character-box/grid positioning, alignment rules and character sets (upper/lower case, numerals and marks) to ensure consistent, legible text on technical drawings and other CAD deliverables.

Keywords: ISO 3098-5, CAD lettering, technical product documentation, lettering standard, CAD fonts, drafting.

Key Topics

• Scope and Purpose
  • General requirements for CAD lettering in accordance with the other parts of ISO 3098.
  • Intended for use on technical drawings and product documentation produced by CADD systems.
• Lettering Types
  • Four CAD lettering styles defined: CB vertical (V), CB sloped (S), CA vertical (V) and CA sloped (S), with CB as preferred application.
  • CA values may be reduced by a factor to approximate traditional lettering type A (refer to the standard for exact rules).
• Spacing Arrangements
  • Tabular spacing (T) and proportional spacing (P) arrangements with defined behavior for character placement.
• Character Box and Grid
  • Each graphic character is defined within a character box and positioned by an internal grid system to control dimensions, shape and location.
  • Tabled dimension values (e.g., line widths, x‑height, spacing) are provided for different lettering heights-see Table 1 in the standard.
• Character Sets
  • Detailed tables for upper-case, lower-case, numerals and marks, with a numeric coding scheme (e.g., 001/... for upper-case) to identify characters and diacritics.
• Alignment Rules
  • Points of alignment for characters, lines and text blocks; decimal numbers align on the decimal sign (comma as per IEC/ISO directives).
• Designation
  • Format for designating a graphic character set (example: “Lettering ISO 3098 - CB PVL - 3,5”).

Applications

• Standardizing text on engineering and manufacturing drawings for clarity and interchangeability.
• Implementing CAD fonts and automated/NC lettering in CAD/CAM systems and drawing templates.
• Ensuring consistent documentation for quality assurance, fabrication, procurement and archival records.
• Useful in industries producing technical drawings: mechanical engineering, aerospace, automotive, electrical, and technical publishing.

Who uses it: CAD managers, drafters, technical illustrators, design engineers, standards compliance officers and CAD software developers.

Related Standards

• ISO 3098-0:1997 - Lettering - Part 0: General requirements.
• ISO 3098 (Parts 1–4) - Characters currently used, Greek, diacritical marks, Cyrillic.
• ISO/TR 10623:1991 - Vocabulary for computer‑aided design and draughting.

Adopting ISO 3098-5 helps maintain legible, machine‑compatible lettering in technical product documentation and improves interoperability across CAD systems and organizations.