ISO 11381:2016

Overview

ISO 11381:2016 - Ophthalmic optics - Spectacle frames - Screw threads specifies ISO metric screw-thread requirements specifically for spectacle frames. It defines the nominal thread sizes used in eyewear (S0,8 × 0,2; M1,0 × 0,25; M1,2 × 0,25; M1,4 × 0,3; M1,6 × 0,35; M2,0 × 0,4), required classes of fit, and the related requirements for taps and gauges. The standard also gives definitions for screw length measurement by head type and a tolerance on nominal lengths.

Key topics and technical requirements

• Covered thread sizes: S0.8×0.2 and metric sizes M1.0, M1.2, M1.4, M1.6 and M2.0 with specified pitches.
• Classes of fit: Tabled classes of fit are provided for nuts and screws used in spectacle components (see standard for full table). Example designation format: M1,6 × 0,35 – 6H/6h (nut/screw fit).
• Thread standards referenced:
  • S0,8 × 0,2 complies with ISO 1501 (miniature threads)
  • M1.0–M2.0 sizes comply with ISO 965‑3 (tolerances for constructional metric threads)
• Taps and gauges: Screwing taps for M1.0–M2.0 shall comply with ISO 529; gauges shall comply with ISO 1502. (Note: taps for S0.8×0.2 are not specified in an international standard.)
• Screw length definitions and tolerance: The standard defines how to measure nominal length for different head types (flat, countersunk, fillister, pan/cheese) and specifies a length tolerance of 0 mm to −0.15 mm.
• Informative guidance: Annex A maps common thread sizes to their typical uses in frames (e.g., pads, joints, closing blocks).

Applications and practical value

• Ensures interchangeability of screws and threaded parts across spectacle manufacturers and suppliers.
• Supports consistent fit and function for small precision threads used in hinges, pads, joint blocks and closing mechanisms of eyewear.
• Aids designers and engineers in selecting the correct thread size, fit class and length tolerances for frame components.
• Guides manufacturers, component suppliers, toolmakers and quality inspectors on required taps, gauges, and inspection criteria for production and servicing.
• Benefits repair and maintenance workflows by standardizing replacement screws and threaded inserts.

Who should use this standard

• Eyewear frame designers and manufacturers
• Ophthalmic laboratories and repair technicians
• Fastener and miniature-thread component suppliers
• Tooling and gauge manufacturers
• Quality assurance and regulatory teams in ophthalmic optics

Related standards

• ISO 1501 - miniature screw threads
• ISO 965‑3 - metric screw thread tolerances (constructional)
• ISO 529 - short machine taps and hand taps
• ISO 1502 - gauges and gauging

Keywords: ISO 11381:2016, spectacle frames, screw threads, ophthalmic optics, ISO metric threads, taps, gauges, M1.6×0.35, thread classes, screw length tolerance.