ISO 965-2:1998

Overview

ISO 965-2:1998 is a crucial international standard developed by the International Organization for Standardization (ISO) focusing on general purpose metric screw threads. This part of the ISO 965 series specifically details the tolerances and limits of sizes for external and internal screw threads of medium quality. It applies to the sizes and dimensions of ISO metric threads commonly used for fasteners and mechanical assemblies, ensuring compatibility and interchangeability across global industries.

The third edition, published in December 1998, builds on previous revisions and aligns with other related ISO standards such as ISO 68-1 for basic thread profiles and ISO 262 for bolt dimensions. ISO 965-2 standardizes thread diameters, flank diameters, and other critical dimensions for medium quality screw threads, providing precise limit sizes for manufacturing and quality assurance purposes.

Key Topics

• Thread Types Covered: General purpose external and internal screw threads, covering both coarse (series à pas gros) and fine (series à pas fin) pitch ranges.
• Medium Quality Class: The standard addresses threads designated with tolerance classes 5H, 6H for internal threads and 6h, 6g for external threads, tailored for medium-level precision applications.
• Dimension Limits: Defines maximum and minimum sizes for diameter on flanks, pitch diameters, and the minor/core diameters for internal and external threads.
• Length of Engagement: Specifies thread length groups as “normal” for consistent manufacturing assessment.
• Coating Considerations: Addresses dimensional tolerance application for coated threads, particularly thin layers like electrolytic deposits, ensuring that post-coating dimensions remain within maximum material limits.
• Thread Profiles and Designation: Complies with ISO 68-1 for thread profile fundamentals and ISO 965-1 for designation rules.

Applications

ISO 965-2:1998 plays a vital role in engineering, manufacturing, and quality control processes that involve metric threaded fasteners such as bolts and nuts. Key applications include:

• Machinery and Equipment Fabrication: Ensures threads meet dimensional tolerances for reliable assembly and disassembly without compromising mechanical strength.
• Automotive and Aerospace Engineering: Provides standardized thread sizing for fasteners critical to safety and performance.
• Construction and Infrastructure: Used in structural bolting systems where medium quality threads balance cost and durability.
• Industrial Fastener Production: Guides manufacturers in producing metric screw threads that conform to international tolerances, facilitating global trade.
• Surface Treatment and Coating: Assists in defining acceptable dimensional changes post-treatment, preserving thread integrity.

Related Standards

To fully apply ISO 965-2:1998 correctly, users should also consider referencing the following interconnected ISO standards:

• ISO 68-1: Basic Profile of ISO General Purpose Metric Screw Threads – foundational profile and geometry.
• ISO 262: Selection of Sizes for ISO General Purpose Metric Fasteners – defines appropriate dimensional ranges for bolts and nuts.
• ISO 965-1: Principles and Fundamental Data for Tolerances of ISO Metric Threads – outlines basic tolerance principles and definitions.
• ISO 5408: Vocabulary for Cylindrical Screw Threads – essential terminology for thread standardization.
• Other ISO 965 Parts:
  • Part 3: Deviations for Construction Threads
  • Part 4: Limits for Hot-Dip Galvanized External Threads
  • Part 5: Limits for Internal Threads Mating Galvanized External Threads

Keywords: ISO 965-2, metric screw threads, ISO metric threads, screw thread tolerances, medium quality threads, external threads, internal threads, general purpose threads, screw thread dimensions, mechanical fasteners, thread size limits, thread coating tolerances, ISO standards for threads.