ISO 6157-2:1995 PDF

Overview

ISO 6157-2:1995 - “Fasteners - Surface discontinuities - Part 2: Nuts” defines acceptable limits and inspection practices for surface defects on nuts. It covers nuts with nominal thread diameters 5 mm to 39 mm, product grades A and B, and all mechanical property classes referenced in ISO 898-2 and ISO 898-6 (unless otherwise agreed). The standard ensures that visible surface discontinuities do not impair the mechanical or functional properties required by related fastener standards.

Key topics and technical requirements

• Types of surface discontinuities covered: cracks (quench, forging, inclusion, locking element, washer-retainer), shear bursts, bursts, seams, folds, voids, tool marks and general damages.
• Quantitative limits and definitions:
  • Cracks: e.g., forging cracks - max two that extend across the bearing face, neither deeper than 0.05·d; no crack shall extend into the tapped hole beyond the first full thread; cracks in the first full thread ≤ 0.5·H1 (H1 = 0.541·P).
  • Seams: permitted up to a depth of 0.05·d.
  • Voids: depth h