Overview
ISO 965-1:2013 - "ISO general purpose metric screw threads - Tolerances - Part 1: Principles and basic data" defines the tolerance system for ISO general purpose metric screw threads (M) as specified in ISO 261. The standard references the basic thread profile in ISO 68-1 and establishes the principles, symbols and basic data used to calculate and apply thread tolerances for major, pitch and minor diameters.
Key topics
- Tolerance system: Combination of tolerance grades (numbers, e.g., 4, 6, 8) and tolerance positions (letters, e.g., H, G, h, g). Example designations: 6H, 6g.
- Fundamental deviations: Standardized deviations for internal and external threads (tables for EI, es) by pitch to manage clearance and assembly.
- Diameter tolerances: Tables and rules for major, pitch and minor diameter tolerances for internal (D, D1, D2) and external (d, d1, d2) threads, covering multiple tolerance qualities and diameter ranges.
- Length of thread engagement: Guidance for short/normal/long engagement groups (S, N, L) and their impact on tolerance selection.
- Multiple-start threads, root contours and formulas: Definitions, formulae for fundamental deviations and tolerances, and root/truncation requirements.
- Designation rules: How to designate single- and multiple-start and left-hand threads.
- Compatibility considerations: Recommendations for coated threads and combinations of internal/external tolerance classes.
Applications
ISO 965-1:2013 is used to:
- Specify thread tolerances in part drawings and procurement documents for metric fasteners and threaded components.
- Select tolerance classes (e.g., 6H/6g) to achieve desired fit (clearance/interference) between internal and external threads.
- Define manufacturing and inspection criteria for production, including gauging referenced in ISO 1502.
- Address effects of coatings (plating, galvanizing) and ensure post-coating fit (links to Parts 4 and 5 of ISO 965).
Typical users:
- Mechanical designers and CAD engineers
- Manufacturing and production engineers
- Threaded fastener and component manufacturers
- Quality, metrology and inspection personnel
- Standards specialists and procurement teams
Related standards
- ISO 68-1 - Basic profile for metric screw threads
- ISO 261 - General plan for ISO general purpose metric screw threads
- ISO 1502 - Gauges and gauging for metric threads
- Other parts of ISO 965: Part 2 (limits of sizes - medium quality), Part 3 (constructional deviations), Part 4 & 5 (hot-dip galvanized threads)
ISO 965-1:2013 is essential when you need consistent, interoperable specifications for metric screw thread tolerances, ensuring reliable assembly, interchangeability and compliance across manufacturing and supply chains.
Open preview (PDF)ISO general purpose metric screw threads — Tolerances — Part 1: Principles and basic data