Overview
EN ISO 8741:2025 - Fasteners - Reverse-taper grooved pins - Half-length progressive grooves (ISO 8741:2025) is a CEN-adopted International Standard that specifies the characteristics of reverse‑taper grooved pins with closed, half‑length progressive grooves. It covers pins manufactured in steel and stainless steel, with nominal diameters from 1 mm to 25 mm, intended for positioning, guiding and allowing relative rotation of assembled parts. The standard emphasizes easy installation (shape-assisted) and medium pull‑out resistance (elastic fit behaviour). General functional principles and assembly requirements are referenced to ISO 13669.
Key topics and technical requirements
- Geometry and dimensions: Defines pin form (rounded ends by default; chamfered ends optional), groove arrangement (progressive grooves occupying half the pin length), and dimensional limits for nominal diameters 1–25 mm.
- Groove location and length tolerances: Grooves must remain closed at pin ends; maximum distance from end to start of grooves depends on pin length (ranges given). Groove length is specified as l/2 with defined tolerances (e.g., ±0.3 mm for short pins up to ±1.5 mm for long pins).
- Control of expanded diameter and straightness: Measurement and acceptance criteria for expanded diameter (d) and pin straightness are handled in accordance with ISO 13669. For coated pins, dimensions apply prior to coating.
- Materials and grades: Standard covers steel and stainless steel; stainless‑steel grades A2, A4, C1 and F1 are included. Other materials (e.g., hardened steel, brass, aluminium) may be used by agreement.
- Mechanical and inspection requirements: References normative standards for mechanical properties, coatings and inspection (see Related Standards).
- Updates in 2025 edition: Technical revisions from the 1997 edition include new non‑preferred diameters (1 mm, 3.5 mm, 7 mm, 9 mm, 14 mm, 18 mm), updated expanded diameter values for short lengths, added stainless steel values, and new labelling specifications (Clause 8).
Applications and users
- Typical uses: Positioning and guiding components, providing controlled relative rotation, fixtures, jigs, and assemblies in machinery, automotive components, consumer goods and precision equipment.
- Who uses this standard: Fastener manufacturers, mechanical design engineers, quality and procurement teams, inspection laboratories, and standards committees. EN ISO 8741:2025 guides selection, production tolerances, acceptance inspection and supplier communication for reverse‑taper grooved pins.
Related standards
EN ISO 8741:2025 is essential when specifying or sourcing reverse‑taper grooved pins to ensure interchangeability, consistent performance and compliance with current European and international fastener practice.
