oSIST prEN ISO 888:2026

• Abstract:

  ISO 888:2012 specifies lengths and thread lengths for bolts, screws and studs for use in appropriate product standards and other relevant documents, e.g. for parts per drawing.; It applies to bolts, screws and studs with ISO metric screw thread according to ISO 68-1.

• Status: Not Published
• Public Enquiry End Date: 09-Sep-2026
• ICS: 21.060.10 - Bolts, screws, studs
• Technical Committee: ISEL - Mechanical elements
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 14-Jul-2026
• Due Date: 01-Dec-2026
• Completion Date: 11-Sep-2026
• Ref Project: prEN ISO 888 - Fasteners - Bolts, screws and studs - Nominal lengths and thread lengths (ISO/DIS 888:2026)

• Revises: SIST EN ISO 888:2018 - Fasteners - Bolts, screws and studs - Nominal lengths and thread lengths (ISO 888:2012)
• Effective Date: 08-Nov-2023

Overview

oSIST prEN ISO 888:2026 - Fasteners - Bolts, screws and studs - Nominal lengths and thread lengths - establishes internationally recognized requirements for the nominal lengths and thread lengths of bolts, screws, and studs. This standard, prepared by the Slovenian Institute for Standardization (SIST) and based on ISO/DIS 888:2026, applies to fasteners with ISO metric screw threads as specified in ISO 68-1. The document defines terminology, length measurements, dimensional tolerances, and thread engagement requirements to guide the consistent selection and specification of mechanical fasteners for general industrial use.

Key Topics

• Scope and Applicability

  • Applies to bolts, screws, and studs with ISO metric screw threads according to ISO 68-1.
  • Requirements pertain to use in product standards, part drawings, and industry documentation.
  • When different values are needed (e.g., for structural bolting), product standards take precedence.

• Definitions and Symbols

  • Relies on standardized terms and definitions from ISO 225 and ISO 1891-1, ensuring consistent industry language.
  • Specifies commonly used symbols for thread length (b), nominal length (l), and other dimensional characteristics.

• Nominal Lengths

  • Comprehensive tables provide standard nominal lengths from 2 mm up to 1,000 mm, enabling accurate specification for a wide range of applications.
  • Outlines preferred and non-preferred sizes for product selection.
  • Details tolerances according to ISO 4759-1, supporting manufacturing quality.

• Thread Lengths

  • Calculation methods for thread lengths (b) based on the nominal length (l) and thread diameter (d).
  • Defines fully threaded vs. partially threaded fasteners and their applicable sizes.
  • Specific recommendations for stainless steel fasteners with reduced loadability (in line with ISO 3506-1).

• Designation of Fastener Types

  • Covers various fastener types, including those with hexagon heads, countersunk heads, headless designs, and studs.
  • Provides clear rules for defining lengths for different fastener head shapes and ends.

Applications

Implementing the ISO 888:2026 standard enhances reliability, efficiency, and interchangeability in numerous industries, including:

• Mechanical Engineering: Standardizes fastener selection for assemblies, improving compatibility and simplifying procurement.
• Manufacturing & Production: Facilitates consistent product quality, batch control, and inventory management by defining clear fastener sizing rules.
• Construction: Supports structural integrity by prescribing correct length and thread engagement for bolts and studs in building assemblies.
• Maintenance & Repairs: Assures replacement fasteners meet original specification, enabling safe, straightforward maintenance operations.
• Product Design & Specification: Allows designers and engineers to reference globally accepted length and threading practices in technical documentation and CAD/BOM systems.

Related Standards

For comprehensive fastener management and selection, consider referencing the following interconnected standards:

• ISO 68-1 – Basic and design profiles for ISO metric screw threads.
• ISO 225 – Symbols and descriptions of dimensions for bolts, screws, studs, and nuts.
• ISO 1891-1 – Fastener vocabulary and designations.
• ISO 3506-1 – Mechanical properties for corrosion-resistant stainless steel fasteners.
• ISO 4753 – Ends of parts with external ISO metric threads.
• ISO 4759-1 – Tolerances for fasteners, including bolts, screws, studs, and nuts (Product grades A, B, and C).
• ISO 4014, ISO 4017, ISO 8765, ISO 8676, ISO 10642 – Detailed product standards for various fastener types.

Adhering to oSIST prEN ISO 888:2026 ensures optimal compatibility, safety, and performance in all applications using metric fasteners, while supporting global harmonization of engineering practices.

SLOVENSKI STANDARD
01-september-2026
Vezni elementi - Sorniki, vijaki in zatiči - Imenske dožine in dolžine navoja (ISO/DIS
888:2026)
Fasteners - Bolts, screws and studs - Nominal lengths and thread lengths (ISO/DIS
888:2026)
Verbindungselemente - Schrauben - Nenn- und Gewindelängen (ISO/DIS 888:2026)
Fixations - Vis, goujons et tiges filetées - Longueurs nominales et longueurs filetées
(ISO/DIS 888:2026)
Ta slovenski standard je istoveten z: prEN ISO 888
ICS:
21.060.10 Sorniki, vijaki, stebelni vijaki Bolts, screws, studs
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 888
ISO/TC 2/SC 7
Fasteners — Bolts, screws and studs
Secretariat: DIN
— Nominal lengths and thread
Voting begins on:
lengths
2026-06-22
Fixations — Vis, goujons et tiges filetées — Longueurs nominales
et longueurs filetées
Voting terminates on:
2026-09-14
ICS: 21.060.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 888:2026(en)
ISO/DIS 888:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO/DIS 888:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 Position of lengths and thread lengths . 2
5.1 General .2
5.2 Bolts and screws .2
5.3 Headless screws and set screws .3
5.4 Studs and similar fasteners . .4
6 Dimensions and tolerances for lengths, l . . 5
7 Dimensions and tolerances for thread lengths, b . 8
8 Limits for standard nominal lengths l (shortest and longest standard lengths) . 9
nom
8.1 Hexagon head bolts (partially threaded) .9
8.2 Non-hexagon head bolts (partially threaded) .10
8.3 Screws (fully threaded) with effective bearing surface perpendicular to the axis.10
8.4 Bolts and screws with countersunk head .10
8.5 Limits between fully threaded and partially threaded screws .11
Bibliography .12

iii
ISO/DIS 888:2026(en)
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 888 was prepared by Technical Committee ISO/TC 2, Fasteners, Subcommittee SC 7, Reference standards.
This third edition cancels and replaces the second edition (ISO 888:2012), which has been technically
revised.
The main changes are as follows:
— terms and definitions have been added;
— standard nominal lengths have been extended to longer lengths, for bolts with diameters up to 100 mm
(in relation to the development of ISO 898-11), fully threaded rods or other long fasteners (see Clause 6);
— nominal diameters M3,5 and M7 have been added;
— formula for l with regards to l and the 5P difference remained unchanged, but P has been
s,min g,max
specified as always being the coarse pitch value (even for bolts with fine pitch thread);
— for stainless steel fasteners with reduced loadability due to head design and in accordance with
ISO 3506-1, thread length b ≥ 3d have been recommended (see 7);
— the limits for the shortest and longest standard nominal lengths l have been recorded, to make them
nom
traceable (see Clause 8);
— existing limits between partially threaded and fully threaded bolt and screws (when both are specified
in the same product standard) have been recorded (see 8.5).

iv
DRAFT International Standard ISO/DIS 888:2026(en)
Fasteners — Bolts, screws and studs — Nominal lengths and
thread lengths
1 Scope
This document specifies lengths and thread lengths of bolts, screws and studs for use in appropriate product
standards and other relevant documents, e.g. for parts per drawing.
It applies to bolts, screws and studs with ISO metric thread in accordance with ISO 68-1.
When other lengths or thread lengths are specified (e.g. for structural bolting), the values specified in the
product standard supersede this document.
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 68-1, ISO general purpose screw threads — Basic and design profiles — Part 1: Metric screw threads
ISO 225, Fasteners — Bolts, screws, studs and nuts — Symbols and descriptions of dimensions
ISO 1891-1, Fasteners — Vocabulary — Part 1: Designations of fasteners and their features
ISO 3506-1, Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 1: Bolts,
screws and studs with specified grades and property classes
ISO 4753, Fasteners — Ends of parts with external ISO metric thread
ISO 4759-1, Tolerances for fasteners — Part 1: Bolts, screws, studs and nuts — Product grades A, B and C
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 225 and ISO 1891-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols
b thread length, mm
b , b thread lengths of double-end stud, mm
1 2
b thread length of the stud metal end, mm
m
d nominal thread diameter of the bolt, screw or stud, mm
l nominal length of the bolt, screw or stud, mm

ISO/DIS 888:2026(en)
l distance from the bearing face to the first full formed thread of bolt with unthreaded shank, mm
g
l length of the unthreaded shank, mm
s
P pitch of the thread, mm
5 Position of lengths and thread lengths
5.1 General
The position of length l and thread length b for bolts, screws and studs is specified in ISO 225.
Points and ends for bolts and screws are usually included in the length and thread length except for the pilot
point, as specified in ISO 4753.
5.2 Bolts and screws
For bolts and screws with effective bearing surface perpendicular to the axis, the length l shall be defined
from the bearing face to the end of the bolt or screw; see Figure 1.
Figure 1 — Length for bolts and screws with effective bearing surface perpendicular to the axis
For bolts and screws with flat countersunk head, the length l shall be defined from the upper edge of the
head to the end of the bolt or screw; see Figure 2.
Figure 2 — Length for bolts and screws with flat countersunk head
For bolts and screws with raised countersunk head, the length l shall be defined from the theoretical
intersection of the top surface of the head with the head diameter to the end of the bolt or screw; see Figure 3.
Figure 3 — Length for bolts and screws with raised countersunk head

ISO/DIS 888:2026(en)
For concave bearing surfaces, serrated bearing surfaces and similar, the length l shall be defined from the
effective bearing plane of the bearing face to the end of the bolt or screw; see Figures 4 and 5.
Figure 4 — Length for bolts and screws with concave bearing surface
Figure 5 — Length for bolts and screws with serrated bearing face
Figure 6 — Length for bolts and screws with captive washer
5.3 Headless screws and set sc
...