ISO 15786:2008

Technical drawings - Simplified representation and dimensioning of holes

ISO 15786:2008 specifies rules for the simplified representation, dimensioning and tolerancing of holes, counterbores, internal threads and chamfers on drawings.

Dessins techniques — Représentation et cotation simplifiées des trous

General Information

• Status: Published
• Publication Date: 01-Oct-2008
• ICS: 01.100.20 - Mechanical engineering drawings
• Technical Committee: ISO/TC 10/SC 6 - Mechanical engineering documentation
• Drafting Committee: ISO/TC 10/SC 6 - Mechanical engineering documentation
• Current Stage: 9093 - International Standard confirmed

Overview

ISO 15786:2008 - Technical drawings - Simplified representation and dimensioning of holes - defines rules for how to show, dimension and toleranced holes, counterbores, internal threads and chamfers on engineering drawings using simplified graphical and textual conventions. It specifies when simplified methods are acceptable and when complete representations (cuts, sections, enlarged views) must be used to avoid ambiguity.

Key SEO phrases: ISO 15786:2008, technical drawings, simplified representation, dimensioning of holes, counterbores, internal threads, chamfers, tolerancing.

Key topics and requirements

• Methods of representation

  • Complete representation and complete dimensioning (full views, sections) when simplification could mislead.
  • Complete representation with simplified dimensioning.
  • Simplified representation and simplified dimensioning (only centre lines or symbolic markers).

• Structure and sequence

  • Simplified dimensioning is a vertical sequence of descriptive elements arranged largest-to-smallest (symbols, nominal sizes, depths, tolerances).
  • Use consistent character sizing and single-line instructions for identical features or groups.

• Graphical symbols

  • Standard symbols include ∅ (diameter), square symbol, and hole‑bottom symbols U, V, W.
  • Countersink/chamfer shown by largest diameter × angle; depths by the multiplication sign × and threaded/cored distinctions using a slash / (e.g., M10×25/30).

• Groups and repetition

  • Indicate number of groups and holes per group with notation such as 3×/5× ∅10 or 5× ∅10; use textual descriptions only where necessary (avoid for automated data transfer).

• Tolerancing & surface finishes

  • Dimensions must be toleranced (direct tolerances or general tolerances such as ISO 2768‑1).
  • Surface texture and geometrical tolerances follow ISO GPS standards referenced by ISO 15786.

• Leader lines & orientation

  • Leader lines terminate at hole centres or at the intersection of the centre line and visible edge; arrow direction indicates the surface from which features are manufactured.

Practical applications and users

Who benefits:

• Mechanical drafters and CAD technicians creating standardized drawings.
• Design engineers specifying holes, threads and countersinks for manufacturability.
• Manufacturing engineers and machinists interpreting production drawings.
• Quality/control engineers inspecting features to specified tolerances.
• Technical publications teams and organizations using automated drawing data exchange.

Typical uses:

• Producing concise, unambiguous manufacturing drawings for machined parts.
• Reducing drawing clutter by using simplified notation where appropriate.
• Standardizing cross-company drawing conventions for procurement and inspection.

Related standards

ISO 15786 references and complements other drawing and GPS standards, including:

• ISO 128 series (views, sections, leader lines)
• ISO 129‑1 (dimensioning principles)
• ISO 406 (dimension tolerancing)
• ISO 1101, ISO 5458 (geometrical tolerancing)
• ISO 1302 (surface texture)
• ISO 6410‑3 (simplified thread representation)
• ISO 2768‑1 (general dimensional tolerances)

Using ISO 15786:2008 helps ensure clear, consistent hole representation and dimensioning across engineering and manufacturing workflows.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 15786
First edition
2008-10-01
Technical drawings — Simplified
representation and dimensioning of holes
Dessins techniques — Représentation et cotation simplifiées des trous

Reference number
©
ISO 2008
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ii © ISO 2008 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Methods of representation and dimensioning of holes. 2
4.1 Complete representation and complete dimensioning of holes. 2
4.2 Complete representation and simplified dimensioning of holes. 2
4.3 Simplified representation and simplified dimensioning of holes. 2
4.4 Representation of holes on the same drawing. 2
5 Structure of dimensioning of holes . 3
5.1 Structure and sequence of descriptive elements for simplified dimensioning of holes . 3
5.2 Graphical symbols. 4
5.3 Number of groups of holes and number of holes in a group. 6
5.4 Indication of tolerances. 7
5.5 Hole bottom . 7
5.6 Countersinks and chamfers . 7
5.7 Depth dimensions. 8
5.8 Indication of surface texture. 10
5.9 Indication of dimensions on geometrical tolerances. 12
Annex A (informative) Examples for representation and dimensioning of holes, counterbores and
internal threads . 13
Bibliography . 18

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 15786 was prepared by Technical Committee ISO/TC 10, Technical product documentation,
Subcommittee SC 6, Mechanical engineering documentation.
iv © ISO 2008 – All rights reserved

Introduction
This International Standard has been established to specify the simplified representation and dimensioning of
holes.
The rules established by this International Standard determine, unambiguously, methods for the
representation — both complete and simplified — and the dimensioning of holes, as well as the structure and
sequence of the descriptive elements for the simplified representation of holes.

INTERNATIONAL STANDARD ISO 15786:2008(E)

Technical drawings — Simplified representation and
dimensioning of holes
1 Scope
This International Standard specifies rules for the simplified representation, dimensioning and tolerancing of
holes, counterbores, internal threads and chamfers on drawings.
Where there could be misinterpretation using simplified representation, the complete representation and
dimensioning by cuts, sections or elements on a larger scale apply, according to ISO 128-30, ISO 128-34,
ISO 128-40, ISO 128-44, ISO 128-50, ISO 129-1 and ISO 406.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 128-22, Technical drawings — General principles of presentation — Part 22: Basic conventions and
applications for leader lines and reference lines
ISO 128-30, Technical drawings — General principles of presentation — Part 30: Basic conventions for views
ISO 128-34, Technical drawings — General principles of presentation — Part 34: Views on mechanical
engineering drawings
ISO 128-40, Technical drawings — General principles of presentation — Part 40: Basic conventions for cuts
and sections
ISO 128-44, Technical drawings — General principles of presentation — Part 44: Sections on mechanical
engineering drawings
ISO 128-50, Technical drawings — General principles of presentation — Part 50: Basic conventions for
representing areas on cuts and sections
ISO 129-1, Technical drawings — Indication of dimensions and tolerances — Part 1: General principles
ISO 406, Technical drawings — Tolerancing of linear and angular dimensions
ISO 1101, Geometrical Product Specifications (GPS) — Geometrical tolerancing — Tolerances of form,
orientation, location and run-out
ISO 1302, Geometrical Product Specifications (GPS) — Indication of surface texture in technical product
documentation
ISO 5458, Geometrical Product Specifications (GPS) — Geometrical tolerancing — Positional tolerancing
ISO 6410-3:1993, Technical drawings — Screw threads and threaded parts — Part 3: Simplified
representation
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
complete representation of holes
representation of holes in accordance with generally valid rules and projection methods for technical drawings
3.2
simplified representation of holes
representation of holes, drawn either true to scale or not, with a symbolic representation of the features
3.3
complete dimensioning of holes
dimensioning of holes using dimension lines and extension lines
3.4
simplified dimensioning of holes
dimensioning of holes using leader lines and reference lines
4 Methods of representation and dimensioning of holes
4.1 Complete representation and complete dimensioning of holes
The complete representation and dimensioning of holes according to ISO 128-30, ISO 128-34, ISO 128-40,
ISO 128-44, ISO 128-50 and ISO 129-1 applies in all cases where a simplified representation of holes and
dimensioning could lead to misinterpretation of the drawing (see Table 1).
4.2 Complete representation and simplified dimensioning of holes
Representation and dimensioning of holes in the sections is preferred. For dimensioning in the sections, the
leader line is directed towards the point of intersections of the visible edge of the part and the centre line of the
hole, ending with an arrowhead on the centre line of the hole. For dimensioning in the view from above, the
leader line is directed towards the centre of the hole, ending with an arrowhead on the outline of the hole (see
Table 1). For rules relative to the use of leader lines and reference lines, see ISO 128-22.
4.3 Simplified representation and simplified dimensioning of holes
For simplified representation and simplified dimensioning of holes, only the centre lines of the holes are shown.
In the case of the view from above, the location of the centre of the hole is represented by a cross using
continuous wide lines (according to ISO 128-24:1999, type 01.2). The location of holes represented parallel to
the plane of projection is shown by a long-dashed dotted narrow line (according to ISO 128-24:1999,
type 04.1).
In the case of simplified dimensioning, the leader line ends with an arrowhead at the centre of the hole or at
the point of intersection of the visible edge of the part and the centre line of the hole. The arrowhead points to
the surface of the part from which the features are indicated (direction of manufacture; exception, see 5.3)
(see Table 1).
4.4 Representation of holes on the same drawing
It is suggested that holes should be drawn and represented using only one of the methods of Table 1 to avoid
causing confusion on the same drawing.
2 © ISO 2008 – All rights reserved

Table 1 — Comparison of methods for representation and dimensioning of holes
Complete representation and
Complete representation and Simplified representation and
complete dimensioning
simplified dimensioning simplified dimensioning
according to ISO 129-1
5 Structure of dimensioning of holes
5.1 Structure and sequence of descriptive elements for simplified dimensioning of holes
The structure of the simplified dimensioning of holes is composed of continuous enumeration and
denominations of features used.
This means that the graphical symbols (e.g. ∅) and the dimensions (e.g. diameter, hole depths, tolerances)
are shown one below the other. The feature with the largest dimension shall be shown in the first line.
The data shall be marked in characters of the same size, with the exception of the indication of surface texture
(see 5.8).
The necessary data for each featu
...