ISO 4759-1:2000

Overview

ISO 4759-1:2000 - "Tolerances for fasteners - Part 1: Bolts, screws, studs and nuts - Product grades A, B and C" defines standardized dimensional and geometrical tolerances for ISO metric fasteners. The part covers tolerances for bolts, screws, studs and nuts (product grades A, B and C) and tapping screws (product grade A). Dimensions are given in millimetres and tolerances apply to uncoated parts unless otherwise stated.

Key points

• Product grades: A (most precise), B, C (least precise).
• Thread tolerances are taken from ISO 965‑3; external thread tolerance classes typically specified (e.g., 6g for many grades, 8g possible for grade C).
• Non-thread dimensional tolerances are selected from the ISO system of limits and fits (ISO 286‑1 and ISO 286‑2).
• Geometrical tolerances (form, position, run‑out) follow ISO 1101, ISO 8015 and ISO 2692.
• Tolerances apply before coating - see ISO 4042 for electroplated coatings.

Key topics and technical requirements

• Dimensional tolerances for shank, head, bearing face, thread length, underhead features and related features for bolts, screws, studs and nuts.
• Thread tolerancing: metric thread classes and guidance for constructional threads (ISO 965‑3) and tapping screw threads (ISO 1478).
• Driving and internal features: tolerances for hexagon flats/corners, sockets, cross‑recesses and hexalobular recesses, including references to specific product standards (e.g., ISO 4757, ISO 10664).
• Geometrical tolerances: straightness, coaxiality, total run‑out and positional tolerances with datum definitions referenced to thread or head features.
• Informative annexes: examples of toleranced fasteners, and gauges/measuring devices (Annexes A–C).

Applications and users

ISO 4759-1 is used to ensure interchangeability, production control and inspection of metric fasteners. Typical users:

• Fastener manufacturers and cold‑forming shops defining production tolerances.
• Design engineers and product developers specifying fasteners for assemblies.
• Quality assurance, metrology and inspection laboratories applying gauges and geometric tolerancing.
• Procurement and standards teams creating product specifications or calling up tolerances in drawings.
• Technical writers and standards committees aligning product standards with ISO tolerance practice.

Related standards

Normative and commonly referenced documents include:

• ISO 286‑1 / ISO 286‑2 (limits and fits)
• ISO 965‑3 (metric thread tolerances)
• ISO 1101, ISO 8015, ISO 2692 (geometrical tolerancing)
• ISO 1478, ISO 4757, ISO 4042 and various product standards for specific head/driving forms.

Using ISO 4759‑1 helps manufacturers and engineers apply consistent tolerances for fasteners, improving interchangeability, inspection reliability and product quality.