SIST EN ISO 4759-3:2016

Overview

EN ISO 4759-3:2016 - "Tolerances for fasteners - Part 3: Washers for bolts, screws and nuts - Product grades A, C and F (ISO 4759-3:2016)" is a CEN-adopted international standard that defines dimensional, form and position tolerances for flat washers. It covers washers with nominal diameters from 1 mm to 150 mm, applies to non-captive and captive as well as standard and non-standard washers, and is intended for use in bolted joints together with bolts, screws, studs and nuts.

Key topics and technical requirements

• Product grades: Defines three tolerance bands - F (fine), A (precise) and C (coarse/large) - indicating progressively wider tolerance ranges for dimensional and geometric characteristics.
• Dimensions covered: Tolerances for clearance hole(s), outside diameter, thickness, and chamfers (inner and outer). Chamfer orientation options are specified for captive washers.
• Form & position: Requirements and limits for coaxiality (y), flatness/deflection (z) and thickness variation (Δt). Geometric tolerancing follows ISO 1101 and ISO 2692.
• Measurement conditions: Tolerances apply prior to coating; thickness tolerances are measured after removal of burrs.
• Compatibility note: Washers of grades F and A are intended for use with bolts/screws/studs/nuts of product grades A and B; washers of grade C match fasteners of grade C.
• Normative references and annexes: Annex A draws IT tolerance values and limit deviations from ISO 286‑1 and ISO 286‑2 (standard tolerance grades IT11–IT15 etc.).

Example: thickness tolerances are specified by thickness ranges and product grade (e.g., for very thin washers t ≤ 0.5 mm the permitted thickness deviation is on the order of hundredths of a millimetre and increases for thicker parts).

Practical applications and users

Who uses EN ISO 4759-3:2016:

• Fastener and washer manufacturers - to specify production tolerances and QA acceptance criteria.
• Design and mechanical engineers - to select appropriate washer grades to meet joint performance and assembly requirements.
• Quality/inspection engineers - to prepare inspection plans and sampling criteria for dimensional and geometric checks.
• Purchasing and specification writers - to create unambiguous procurement documents for washers used in bolted assemblies.
• Standards committees and test labs - for conformity assessment and harmonized testing.

Benefits:

• Ensures interchangeability and reliable fit in bolted joints.
• Reduces assembly issues (misfits, uneven bearing, preload loss) by specifying hole, diameter, thickness and form tolerances.
• Improves communication between suppliers and users using standardized product grades.

Related standards

• ISO 4759-1 (bolts, screws, studs and nuts - product grades A, B and C)
• ISO 1101 (geometrical tolerancing)
• ISO 2692 (MMR/LMR requirements)
• ISO 286‑1 / ISO 286‑2 (IT tolerance grades and limit deviations)

Keywords: EN ISO 4759-3:2016, washers tolerances, fastener tolerances, product grades A C F, washers for bolts screws nuts, ISO 4759-3.