SIST EN 26157-1:1996

Overview

EN 26157-1:1991 - Fasteners - Surface discontinuities - Part 1: Bolts, screws and studs for general requirements (ISO 6157-1:1988) is a CEN standard that establishes limits and acceptance criteria for surface discontinuities on common threaded fasteners. The standard applies to bolts, screws and studs with nominal thread diameters of 5 mm and larger, for product grades A and B, and for property classes up to and including 10.9. An annex provides a sampling plan for inspection.

This standard is identical to ISO 6157-1:1988 and has been adopted in national implementations (for example SIST EN 26157-1).

Key topics and technical requirements

• Scope and applicability: Defines which fasteners are covered (diameter ≥ 5 mm, grades A/B, property classes ≤ 10.9).
• Types of surface discontinuities: Describes categories of surface defects that can affect performance and appearance (e.g., laps, cracks, seams, tears) - the standard sets limits for such discontinuities.
• Acceptance criteria: Establishes limits and criteria for when a fastener is acceptable, conditionally acceptable, or rejected due to surface discontinuities.
• Sampling plan: Annex includes a sampling procedure to determine lot conformity without inspecting every item, enabling statistically based quality control.
• Reference to ISO series: Aligned with ISO 6157-1:1988, enabling harmonized inspection and procurement across international markets.

(Note: EN 26157-1 sets the framework and acceptance limits rather than prescriptive manufacturing steps. For detailed inspection techniques or measurement procedures, refer to complementary documents or inspection standards.)

Applications

• Quality control and acceptance testing in fastener manufacturing lines.
• Incoming inspection criteria for suppliers and procurement teams in automotive, construction, machinery and general engineering.
• Defining contractual acceptance criteria in purchase orders and specifications to ensure consistent product quality.
• Guiding inspection plans for third-party auditors and certification bodies.
• Useful for design engineers and maintenance teams who need assurance that fasteners meet surface integrity requirements to avoid fatigue or corrosion initiation.

Who uses this standard

• Fastener manufacturers and production engineers
• Quality assurance and inspection teams
• Procurement and sourcing professionals
• Mechanical designers and reliability engineers
• Third‑party testing and certification bodies

Related standards

• ISO 6157-1:1988 (identical content)
• Other parts of the ISO 6157 series and national adoptions (for full series context and related defect classification)

Keywords: EN 26157-1:1991, fasteners, surface discontinuities, bolts screws studs, ISO 6157-1, sampling plan, nominal thread diameter 5 mm, product grades A B, property class 10.9, CEN.