Overview
EN ISO 6410-3:2021 - "Technical drawings - Screw threads and threaded parts - Part 3: Simplified representation" (CEN adoption of ISO 6410-3:2021) defines rules for the simplified graphical representation of screw threads and threaded parts on technical drawings. It applies when showing the exact thread geometry is unnecessary (for example, in assembly drawings). Screw thread inserts are excluded (see ISO 6410-2).
Key topics and requirements
- Scope and purpose
- Applies to drawings where only essential features are needed; reduces drawing complexity while preserving functional information.
- What not to show
- Edges of chamfers on nuts and heads
- Thread run-outs
- Shape of screw ends
- Undercuts
- Screws and nuts
- When head shape or drive pattern must be indicated, use the standardized simplified symbols/examples given in the standard (Table 1). Typical simplified designations include hexagon head, socket head, countersunk, pan/washer-head, set screws, nuts (hexagon, square, wing, crown), and common drive slots/cross-slots.
- A simplified representation of the opposite threaded end view is not required.
- Small-diameter threads
- Simplification or abbreviated indication is permissible when the drawn diameter is ≤ 6 mm or when a regular pattern of identical holes/threads exists.
- The designation must still include all features normally required by conventional representation and dimensioning (as specified in ISO 6410-1:1993, clause 4.3).
- Designation should be placed on a leader line pointing to the hole centre-line, terminating in an arrowhead (illustrated in Figures 1–4).
- Conformance notes
- The document aligns with ISO 129-1 for certain notation conventions and references ISO 6410-1 for general conventions.
Practical applications
- Use in assembly drawings and higher-level mechanical schematics where thread form detail is unnecessary.
- Saves CAD/drafting time and reduces visual clutter while keeping manufacturing-relevant information.
- Typical users: mechanical engineers, design drafters, CAD technicians, manufacturing engineers, technical product documentation specialists, and standards/quality teams responsible for drawing consistency.
Related standards
- ISO 6410-1:1993 - General conventions for screw threads and threaded parts
- ISO 6410-2 - Screw thread inserts (not covered here)
- ISO 129-1 - Presentation of dimensions and tolerances (notations)
- ISO 225 - Fastener symbols and descriptions
Using EN ISO 6410-3:2021 ensures consistent, economical representation of threaded components across mechanical engineering drawings and assembly documentation.