EN ISO 3098-1:2015 PDF

Overview

EN ISO 3098-1:2015 - Technical product documentation - Lettering - Part 1: General requirements (ISO 3098-1:2015) is the CEN-endorsed European version of the ISO standard that defines the general rules for lettering used in technical product documentation, particularly technical drawings. It replaces EN ISO 3098-0:1997 and establishes conventions applicable to manual and machine-based lettering methods, including CAD/numerically controlled systems.

Key topics and technical requirements

• Scope and purpose: General requirements for lettering consistent with other parts of ISO 3098 (alphabets, diacritics, CAD application).
• Lettering techniques covered:
  • Free-hand lettering (with an underlaid grid)
  • Templates and manual lettering instruments
  • Dry transfer systems
  • Numerically controlled lettering and draughting (CAD) systems
• Legibility rules: Minimum character spacing of twice the line width; may be reduced to one line width for specific character pairs for visual effect (examples: LA, TV, Tr).
• Dimensions and nominal sizes: Letter height (h) defines nominal size. Standard nominal sizes: 1.8, 2.5, 3.5, 5, 7, 10, 14, 20 mm. Line widths and sizing rules reference ISO 128-20.
• Central line and layout: Central (imaginary) line is the datum for character construction and tooling; nominal size and spacing determine central line location.
• Lettering angle: Vertical (upright) or sloped to 75° from horizontal (right inclination).
• Lettering types: Defined types A, B and CAD-oriented CA/CB (vertical and sloped variants) with dimensional tables for x-height, tails, stems, spacing, line width.
• Additional rules: Suitability for common copying processes (diazo, microfilm, fax) and recommendation to interrupt underlining/overlining where letters have tails.

Applications and who uses this standard

EN ISO 3098-1 is essential for professionals involved in:

• Technical drafters and mechanical designers preparing engineering drawings
• CAD users and automation engineers implementing numerically controlled lettering
• Document control and quality assurance teams ensuring drawing consistency
• Technical illustrators, product documentation teams, and manufacturing engineers who rely on legible, standardized text on drawings and instruction sheets