Overview
ISO 238:2016 specifies standard dimensions for reduction sleeves and extension sockets for tools with Morse taper shanks. The document provides, for each type of adaptive tooling, two sets of dimension tables - one in millimetres and the corresponding values in inches - to ensure worldwide interchangeability of tool interfaces. This second edition is a minor revision of ISO 238:1974 and adds an informative Annex A relating the document’s designations to the ISO 13399 data-exchange series.
Key topics and technical requirements
- Scope: Dimensions for (a) reduction sleeves and (b) extension sockets used with Morse taper tool shanks.
- Dimension tables: Separate tables for metric and inch values for every listed sleeve and socket size to support dual-unit manufacturing and procurement.
- Interchangeability: Numerical values ensure compatibility across tools and machines regardless of unit system; mating dimensions conform to ISO 296 (Morse tapers).
- Inside/outside taper geometry: Inside tapers in reduction sleeves and extension sockets are identical to the standard Morse taper of the same number; outside taper lengths may be equal to or greater than standard.
- Length rules for extension sockets: Tables give a minimum overall length (l); a “reinforced minimum” is defined with increased values:
- +5 mm (or 1/4 inch) for inside taper sizes 1–3
- +10 mm (or 1/2 inch) for inside taper sizes 4–5
- Preference for selectable lengths in multiples of 5 mm / 1/4 in or 10 mm / 1/2 in
- Designation method: Simple naming convention (e.g., Morse 4 × 2) denotes outside × inside Morse taper numbers.
- Data mapping: Annex A maps ISO 238 designations to preferred symbols used in ISO 13399 for cutting tool data representation.
Practical applications
- Specifying and procuring reduction sleeves and extension sockets that fit existing Morse-tapered tool shanks.
- Designing or qualifying toolholding systems for lathes, drills and machine tools where consistent tool interface dimensions are critical.
- Ensuring interchangeability in workshops and production lines that mix imperial and metric tooling.
- Populating CAD/CAM, ERP or PLM systems with standardized tooling dimensions through ISO 13399-compatible labels.
Who should use this standard
- Tooling and adapter manufacturers
- Machine tool builders and maintenance teams
- Toolroom engineers and production planners
- Purchasing and quality control personnel specifying tool interfaces
- Data managers integrating tooling information into digital systems (ISO 13399 users)
Related standards
- ISO 296 - Machine tools: self-holding tapers for tool shanks (Morse tapers)
- ISO 13399 - Cutting tool data representation and exchange (for digital mapping)
Keywords: ISO 238:2016, reduction sleeves, extension sockets, Morse taper, dimensions, interchangeability, ISO 296, ISO 13399, tool interfaces, machine tools.
