Overview
EN ISO 129-1:2019/A1:2021 is the CEN-adopted amendment to ISO 129-1:2018, titled Technical product documentation (TPD) - Presentation of dimensions and tolerances - Part 1: General principles. This document defines general principles and accepted conventions for presenting linear dimensions, hole depths and tolerances on engineering drawings and other technical product documentation. The 2020 Amendment clarifies how multiple hole depths are indicated and interpreted on drawings.
Key topics and requirements
- General principles for dimensioning and tolerancing: establishes consistent presentation rules used in technical product documentation to avoid ambiguity in manufacturing and inspection.
- Hole depth notation (amendment specifics): the amendment adds explicit rules for holes:
- When more than one depth is specified (see Figure 39 c) in the standard), all depths shall be taken from the top surface.
- The dimensions presented in Figures 39 c) and d) are equivalent.
- If no depth is specified, the hole is to be interpreted as through the part.
- Drawing conventions and figures: the amendment introduces or updates subfigures (Figures 39 c) and d)) to illustrate the equivalent ways of presenting depths.
- Clarity and unambiguous interpretation: the changes aim to reduce misinterpretation of depth dimensions and ensure consistent application across national standards adopting EN ISO 129-1.
Applications
This amendment and the Part 1 general principles are practical for:
- Design and drafting of engineering drawings and CAD documentation.
- Preparation of manufacturing instructions and technical product documentation (TPD).
- Quality control, inspection plans and acceptance criteria where clear dimension and tolerance presentation is essential.
- Contractual drawings used between OEMs, suppliers and subcontractors to ensure a common interpretation of features such as hole depths.
Who should use this standard
- Mechanical and product design engineers
- CAD technicians and technical drafters
- Manufacturing engineers and CNC programmers
- Quality inspectors and metrology personnel
- Technical authors and standards coordinators in companies producing engineering drawings
Related standards
- ISO 129 series (other parts on presentation of dimensions and tolerances)
- Standards for geometric tolerancing (commonly used alongside ISO 129)
By following EN ISO 129-1:2019/A1:2021, organizations improve the clarity and interoperability of technical drawings, reduce manufacturing errors, and streamline communication between design, production and inspection teams.