ISO 2903-2-2025 PDF

Full title and description

ISO metric trapezoidal screw threads — Tolerances — Part 2: Limits of sizes. This part specifies the limits of sizes for the major, pitch and minor diameters of ISO metric trapezoidal screw threads (Tr) that conform to ISO 2902 and use the basic/design profiles of ISO 2901.

Abstract

This standard defines numerical limits of sizes for major, pitch and minor thread diameters for trapezoidal metric threads, and applies to the set of tolerance classes recommended in the ISO 2903 system (notably 7H, 8H, 9H, 7e, 8e, 8c and 9c). It is intended to be used alongside ISO 2901 (profiles) and ISO 2902 (general plan).

General information

• Status: Published (International Standard).
• Publication date: July 2025 (national listings show availability/approval dated 25 July 2025).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 17.040.10 (Limits and fits); 21.040.10 (Metric screw threads).
• Edition / version: Edition 1, 2025.
• Number of pages: 31 pages in the ISO record (some national/adoption documents and vendors list 31–39 pages depending on front matter).

Scope

This part specifies limits of sizes for the major, pitch and minor diameters of ISO metric trapezoidal screw threads (Tr) that conform to ISO 2902 and have basic and design profiles in accordance with ISO 2901. It applies to the metric trapezoidal threads covered by the seven tolerance classes recommended in the ISO 2903 system and is not intended for special-purpose lead/feed screws with atypical axial-displacement requirements.

Key topics and requirements

• Definition of limit sizes (maximum and minimum permissible sizes) for major, pitch and minor diameters of trapezoidal metric threads.
• Application to specified tolerance classes used for bolt and nut threads (7H, 8H, 9H, 7e, 8e, 8c, 9c).
• Reference to and coordination with ISO 2901 (basic/design profiles) and ISO 2902 (general plan / diameter–pitch series).
• Tabulated limit values and tolerancing rules to support manufacture, inspection and limit-gauge specification.
• Intended to be used by designers, gauge makers and quality/inspection engineers to ensure interchangeability and correct fit of trapezoidal screw-threaded parts.

Typical use and users

Used by mechanical designers, machine builders, fastener manufacturers, gauge-makers, metrology and QA departments, and standards bodies implementing national/adopted versions. Typical applications include traversing and power-transmission threaded spindles where standardized trapezoidal threads are required for interchangeability and controlled fit.

Related standards

ISO 2901 (basic and design profiles), ISO 2902 (general plan / diameter–pitch series), ISO 2903 (tolerances — system; earlier consolidated versions such as ISO 2903:2016), and ISO 2904 (basic dimensions) are directly related and intended to be used together for complete specification of metric trapezoidal threads. National adoptions and parts (e.g., SS‑ISO 2903‑2:2025, BS ISO 2903-2:2025) accompany the ISO publication.

Keywords

trapezoidal thread; metric thread; Tr thread; tolerances; limits of sizes; major diameter; minor diameter; pitch diameter; ISO 2901; ISO 2902; ISO 2903.

FAQ

Q: What is this standard?

A: ISO 2903-2:2025 is Part 2 of the ISO series on metric trapezoidal screw threads addressing the limits of sizes (numerical limits for major, pitch and minor diameters) used in the ISO trapezoidal-thread system.

Q: What does it cover?

A: It covers the limit sizes and associated tolerancing information for trapezoidal metric threads that use the ISO basic and design profiles (ISO 2901) and the general plan (ISO 2902); it applies to the tolerance classes recommended by the ISO 2903 system.

Q: Who typically uses it?

A: Mechanical designers, fastener manufacturers, gauge-makers, production and inspection engineers, standards committees and anyone specifying or verifying trapezoidal screw-threaded parts for interchangeability.

Q: Is it current or superseded?

A: ISO 2903-2:2025 is a current, published ISO International Standard (published July 2025). It complements and updates the ISO trapezoidal-thread family; national adoptions and listings indicate replacement of earlier national/adopted texts linked to ISO 2903/2903:2016. Check the ISO catalogue or your national standards body for the precise effective date of your national adoption.

Q: Is it part of a series?

A: Yes — it is part of the ISO 2900 series for metric trapezoidal screw threads (for example ISO 2901, ISO 2902, ISO 2903, ISO 2904), with this document designated as Part 2 (limits of sizes) within the tolerancing topic.

Q: What are the key keywords?

A: Trapezoidal thread, Tr, metric trapezoidal, tolerances, limits of sizes, major diameter, pitch diameter, minor diameter, ISO 2901, ISO 2902, ISO 2903.