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
Practical uses include setting up default CAD text styles, specifying drawing text sizes for manufacturing drawings, and ensuring legibility across copying and reproduction processes.
Related standards
- ISO 3098 series (other parts):
- Part 2: Latin alphabet, numerals and marks
- Part 3: Greek alphabet
- Part 4: Diacritical and particular marks for Latin alphabet
- Part 5: CAD lettering of Latin alphabet, numerals and marks
- Part 6: Cyrillic alphabet
- ISO 128-20: Technical drawings - General principles of presentation - Basic conventions for lines
Keywords: technical product documentation, ISO 3098-1, lettering standard, CAD lettering, drawing text, lettering dimensions, line width, nominal size, technical drawings, drafting standards.
