Overview
ISO 18388:2016 - Technical product documentation (TPD) - Relief grooves - Types and dimensioning defines a standardized series of relief grooves for shafts and holes used in mechanical engineering. The standard prescribes a limited selection of groove types and dimensional versions (Types E, F, G, H) to reduce unnecessary tool variety, ensure consistent machining clearances, and support clear technical drawings and assembly. Types G and H correspond in shape and dimensions to indexable hard material inserts per ISO 6987.
Key topics
- Scope and purpose
- Relief grooves for rotationally symmetric workpieces (shafts and holes).
- Aim to avoid multiplicity of tools by restricting groove types and sizes.
- Groove types and intended use
- Type E: For cylindrical surfaces where planar surfaces are not highly loaded; suitable when mating parts have large counterbores or do not contact the planar surface.
- Type F: For surfaces perpendicular to each other that are intended for subsequent machining.
- Type G: For parts not subjected to high fatigue loads and where a small included angle is required.
- Type H: For perpendicular surfaces intended for subsequent machining with a greater included angle.
- Dimensioning rules
- Tabulated radius (r), depth (t), widths (f, g) and preferred series (series 1 radii preferred).
- Different dimensional versions for normal and alternating loads; limits for applicable workpiece diameters.
- Restrictions: not applicable to short shoulders and thin-walled parts in some cases.
- Countersink at counterpart
- Minimum countersink dimension (a) values tied to relief groove size (r × t).
- Designation and drawing presentation
- Required designation format: e.g., Relief groove ISO 18388 – E 0,8×0,3.
- Two presentation methods on drawings: conventional detailed representation and simplified representation (use continuous wide line type 01.2 and leader/reference lines per ISO 128-22 and ISO 128-24).
Applications and who uses it
- Mechanical design engineers specifying mating parts, shoulders and clearances.
- Technical drafters and CAD engineers preparing TPD-compliant drawings.
- Manufacturing and CNC programmers selecting tooling and machining sequences.
- Machinists and tooling engineers to avoid unnecessary cutters and ensure correct relief geometry.
- Quality inspectors and acceptance teams verifying groove dimensions and conformity.
Practical benefits include standardized machining clearances, improved interchangeability, clearer fabrication drawings, and reduced tooling costs.
Related standards
- ISO 6987 - Indexable hard material inserts (G and H correspondence).
- ISO 128-22 and ISO 128-24 - Drawing conventions for leader/reference lines and line types used in simplified representation.
Keywords: ISO 18388:2016, relief grooves, technical product documentation, TPD, shaft grooves, hole grooves, groove dimensioning, mechanical engineering drawings.