ISO 4785:1997

Overview

ISO 4785:1997 specifies requirements, dimensions and construction details for straight-bore glass stopcocks for general laboratory use. It defines two series of nominal bore sizes, ground‑zone geometry and surface-finish limits, material recommendations and marking/designation rules to ensure reliable, interchangeable stopcocks used in chemical and analytical laboratories.

Key topics and technical requirements

• Two series of nominal bores
  • Series I: 1, 1.5, 2.5, 4, 6, 10 mm
  • Series II: 1, 1.5, 2, 3, 4, 5, 6, 8, 10 mm
• Ground zone taper and finish
  • Taper: one increment in diameter per ten increments of axial length (tolerance ±0.006 on diameter increment)
  • Surface roughness (centreline average height): ≤ 1 µm, preferably - ** (example: Stopcock ISO 4785, 4 - 18.8)
  • The large end diameter of the ground zone must be permanently marked on the barrel.

Applications and who uses this standard

• Laboratory glassware manufacturers - design and produce stopcocks that are dimensionally interchangeable and meet quality/tolerance requirements.
• Quality control and inspection teams - verify taper, surface finish, material class and marking for conformity.
• Procurement and specification writers - cite ISO 4785 when specifying general‑purpose stopcocks for research, teaching and industrial labs.
• Calibration/test laboratories and standards bodies - use as a reference for compatibility with other lab glassware.

Related standards

Relevant cross‑references cited by ISO 4785 include:

• ISO 3585 (Borosilicate glass 3.3)
• ISO 719 (Hydrolytic resistance test & classification)
• ISO 4803 (Borosilicate glass tubing)
• ISO 468 (Surface roughness parameters)
• ISO 383 (Interchangeable conical ground joints) and other laboratory glassware standards listed in Annex A

Keywords: ISO 4785, laboratory glassware, glass stopcocks, straight‑bore stopcock, borosilicate glass 3.3, ground zone, stopcock dimensions, stopcock tolerances, stopcock designation.