ISO 4156-3-2021 PDF

Full title and description

ISO 4156-3:2021 — Straight cylindrical involute splines — Metric module, side fit — Part 3: Inspection. This part of ISO 4156 provides requirements, guidance and data for the inspection of straight (non-helical) side‑fitting cylindrical involute splines, including limiting dimensions, tolerances, manufacturing deviations and their effects on fits between coaxial spline elements.

Abstract

This document gives inspection dimensions, tolerances and procedures used to verify straight cylindrical involute splines manufactured to the ISO 4156 metric module, side‑fit system. Linear dimensions are expressed in millimetres and angular dimensions in degrees; tables define limiting dimensions and illustrate how manufacturing deviations affect functional fit.

General information

• Status: Published
• Publication date: February 2021 (ISO edition 2, published 02 Feb 2021)
• Publisher: International Organization for Standardization (ISO)
• ICS / categories: 21.120.30 (Keys and keyways, splines)
• Edition / version: Edition 2 (2021). Corrected version noted December 2025.
• Number of pages: 46 pages (ISO metadata; some national bodies list 47 pages).

Scope

ISO 4156-3:2021 applies to straight (non‑helical) cylindrical involute splines with metric module and side fit. It specifies inspection dimensions and related tolerances, describes permissible manufacturing deviations and explains their effect on the fit between mating spline elements, for use in design verification and production inspection. The standard is intended to be used with the geometry and dimension provisions in ISO 4156‑1 and ISO 4156‑2.

Key topics and requirements

• Inspection dimensions and limits for straight cylindrical involute splines.
• Definitions of limiting dimensions, tolerances and permissible manufacturing deviations.
• Guidance on measuring tooth thicknesses, diameters, and flank fits in metric modules.
• Effects of deviations on side‑fit behaviour between coaxial spline elements.
• Tabulated values for common module sizes and recommended inspection practices.

Typical use and users

Used by design engineers, quality/inspection engineers, metrology technicians, and manufacturing engineers in industries that use splined shafts and hubs (automotive, aerospace, power transmission, machine tools, heavy equipment). It is applied during component design verification, incoming inspection, in‑process control and final acceptance testing of splined parts produced to metric module, side‑fit rules.

Related standards

ISO 4156 is a multi‑part series. Closely related documents include ISO 4156‑1 (generalities) and ISO 4156‑2 (dimensions). ISO 4156‑3:2021 revises and replaces ISO 4156‑3:2005 (withdrawn). These parts are intended to be used together for design, manufacture and inspection of metric side‑fit involute splines.

Keywords

involute splines, straight splines, metric module, side fit, inspection, tolerances, spline inspection, tooth thickness, spline dimensions, fit assessment, splined shafts, splined hubs

FAQ

Q: What is this standard?

A: ISO 4156-3:2021 is the part of the ISO 4156 series that specifies inspection dimensions, tolerances and guidance for straight (non‑helical) metric‑module involute splines designed for side fit.

Q: What does it cover?

A: It covers inspection criteria — limiting dimensions, measurement practices, permissible manufacturing deviations and their effects on the functional fit of mating coaxial spline elements. It provides tables of inspection dimensions and guidance for verifying compliance.

Q: Who typically uses it?

A: Mechanical designers, manufacturing and quality engineers, metrology technicians, and standards committees in sectors where splines transmit torque or ensure axial positioning (for example automotive, aerospace and industrial machinery).

Q: Is it current or superseded?

A: ISO 4156-3:2021 is the current edition (edition 2, published February 2021) and replaced ISO 4156-3:2005. A corrected version was recorded in December 2025. For official status and any later amendments, consult the national standards body or ISO.

Q: Is it part of a series?

A: Yes — it is Part 3 of the ISO 4156 series (other parts include generalities and dimensions). The parts are intended to be used together for the complete specification, design and inspection workflow for metric module, side‑fit involute splines.

Q: What are the key keywords?

A: involute splines, straight splines, metric module, side fit, inspection, tolerances, tooth thickness, spline dimensions.