Overview
EN ISO 18388:2019 (ISO 18388:2016) is a Technical Product Documentation (TPD) standard that defines a limited series of relief grooves for shafts and holes used in mechanical engineering. Its purpose is to standardize groove types and dimensioning for general use, reduce unnecessary variety of tooling, and ensure consistent representation on technical drawings. The standard is adopted by CEN as EN ISO 18388:2019.
Key topics and requirements
- Scope & intent: Specifies relief grooves for rotationally symmetric workpieces (shafts and holes) intended for subsequent machining or assembly.
- Groove types: Four principal forms are defined - Type E, F, G, and H. Each type is intended for different interface conditions:
- Type E: for planar surfaces not subject to high fatigue loads, with subsequent machining of cylindrical surface.
- Type F: for perpendicular surfaces intended for subsequent machining.
- Type G: for parts not subjected to high fatigue loads where a small included angle is required.
- Type H: for perpendicular surfaces with a greater included angle, intended for subsequent machining.
- Dimensioning rules: The standard supplies tables of radii (r), depths (t), widths (f/g) and recommended series (series 1 preferred) for different nominal diameters. Dimension tables cover both normal and alternating loads and indicate where certain types are not applicable (e.g., Type G limited for low-fatigue applications).
- Countersink at counterpart: Provides minimum countersink dimension a for mating parts to ensure clearance.
- Designation format: Clear naming convention - e.g., “Relief groove ISO 18388 – E 0,8×0,3” (type letter and r×t).
- Drawing presentation: Two accepted representations - conventional detailed views and simplified symbols. Simplified representation should use a continuous wide line (type 01.2 per ISO 128-24) with leader/reference lines per ISO 128-22.
Practical applications
- Mechanical designers and drafting engineers use EN ISO 18388 to specify standard relief grooves on shafts, bores and shoulders to:
- Prevent interference between mating parts
- Facilitate subsequent machining and assembly
- Reduce tooling variants and simplify production planning
- Manufacturing engineers, CNC programmers and toolmakers use the dimension tables to select cutting tools and set machining operations.
- Quality and inspection teams apply the designation and drawing conventions to verify compliance with documented groove geometries.
Who should use this standard
- Mechanical designers, CAD technicians, production engineers, toolmakers, and quality engineers in automotive, aerospace, general machinery and precision components industries.
Related standards
- ISO 128-22 (leader/reference lines), ISO 128-24 (lines on mechanical drawings) - referenced for drawing presentation.
- ISO 6987 - related to “indexable hard material inserts”; Shapes/dimensions of Types G and H correspond to ISO 6987.
Keywords: EN ISO 18388:2019, ISO 18388:2016, relief grooves, technical product documentation, shafts and holes, groove dimensioning, mechanical engineering drawings.
