ISO 7388-3:2016

Overview

ISO 7388-3:2016 defines the dimensions and designation of retention knobs for tool shanks with a 7/24 taper used in automatic tool changers (ATC). It covers retention knob forms AD, AF, UD, UF, JD and JF, specifying geometry, tolerancing and key features required for reliable interfacing between tool magazines, automatic gripping systems and spindle noses (in accordance with ISO 9270). All dimensions are given in millimetres and the document includes figures and tables for each form and shank size.

Key Topics and Requirements

• Scope & Forms: Dimensions for retention knobs of forms AD, AF (without coolant), UD, UF (without coolant), JD and JF (with/without coolant and optional data medium).
• Dimensional data: Detailed drawings and tables specify diameters, lengths, thread details and chamfers for each shank number and form.
• Tolerancing: Tolerancing rules per ISO 8015; unspecified tolerances default to classes from ISO 2768‑1 (linear/angular) and ISO 2768‑2 (geometrical).
• Material & hardness: Steel selection is at the manufacturer’s discretion but shall meet a tensile strength of at least 2 980 N/mm and hardness 55–60 HRC; no area shall be through‑hardened.
• Sealing & O-ring: O‑rings must conform to ISO 1629 and are included in delivery where applicable.
• Data medium provision: Options for a data medium hole for forms AF/UF; for JF the manufacturer defines the hole to suit the data device.
• Designation: Standardized naming format (e.g., Retention knob ISO 7388-3-AD40; ISO 7388-3-JD40-45 for JD with α = 45°).

Applications and Who Uses This Standard

ISO 7388-3 is used to ensure interchangeability, safety and performance of tool retention systems in automated machining environments. Typical users:

• Machine tool manufacturers specifying ATC interfaces and spindle noses.
• Tool‑holder and retention knob manufacturers producing components to standardized dimensions.
• CNC toolroom engineers and maintenance teams performing retrofits or replacements.
• Procurement and quality engineers establishing acceptance criteria and inspection plans. Practical benefits include improved compatibility between tool magazines and spindles, easier sourcing of replacement retention knobs, and reduced tooling downtime.

Related Standards

• ISO 9270 (spindle noses for 7/24 taper)
• ISO 1629 (rubber and latices - O‑ring nomenclature)
• ISO 2768‑1 / ISO 2768‑2 (general tolerances)
• ISO 8015 (GPS fundamentals)
• ISO 4753 (thread chamfer ends)

Keywords: ISO 7388-3, retention knobs, 7/24 taper, automatic tool changers, tool shanks, retention knob forms AD AF UD UF JD JF, spindle noses, dimensions, tolerances, O‑ring.