ISO 4759-3:2016

Overview

ISO 4759-3:2016 - "Tolerances for fasteners - Part 3: Washers for bolts, screws and nuts - Product grades A, C and F" specifies dimensional and geometrical tolerances for flat washers (nominal diameters 1 mm to 150 mm) used in bolted joints. It covers non-captive and captive washers, standard and non‑standard washers, and can be applied (partially) to non‑flat washers. The standard defines three product grades: F (fine tolerances), A (precise tolerances) and C (large tolerances), and clarifies compatibility with bolt/screw/stud/nut product grades.

Key topics and technical requirements

• Scope and applicability: Washers for bolts, screws, studs and nuts with nominal diameters 1–150 mm; excludes dynamic disc springs.
• Product grades: Grade F (fine), A (precise), C (coarse) - each with defined tolerance ranges for dimensional and geometrical characteristics.
• Dimensional tolerances:
  • Clearance hole (d1) and outside diameter (d2) tolerances given by IT/H classes (see Annex A referencing ISO 286‑1/2).
  • Thickness tolerances specified by ranges (e.g., t ≤ 0.5 mm…10–20 mm) and measured after burr removal.
  • Chamfer dimensions and minimum values for inner/outer chamfers are specified (including optional captive-washer requirements).
• Form and position tolerances:
  • Flatness (deflection) z (effective height vs effective thickness) with limits by thickness and grade.
  • Coaxiality y (concentricity between hole and outer diameter) based on IT grades.
  • Thickness variation Δt limits on the same part at defined ring-width positions.
• Manufacturing notes:
  • Tolerances apply prior to coating.
  • Rollover and fracture features from punching are allowed but may be undefined; specific fracture/rollover considerations are noted.
  • Deviations are permitted only where product standards justify them; product standards take precedence.

Practical applications

• Ensures interchangeability and fit of washers with bolts, screws, studs and nuts in mechanical assemblies.
• Guides designers in specifying washer geometry and tolerance grades for performance and assembly clearance.
• Provides inspection criteria for quality control and incoming‑goods inspection (thickness, flatness, coaxiality).
• Used by manufacturers to set production tolerances, tooling specs and finishing operations (grinding/calibrating to meet flatness).

Who uses this standard

• Fastener manufacturers and tooling designers
• Mechanical and product engineers specifying bolted joints
• Quality/inspection engineers and metrology labs
• Procurement/specification writers for industrial components

Related standards

• ISO 286‑1 / ISO 286‑2 (tolerance grades and limit deviations) - referenced in Annex A
• ISO 1101 and ISO 2692 (geometrical tolerancing and MMR/LMR reciprocity) - normative references

Keywords: ISO 4759-3:2016, washers tolerances, fasteners, product grades A C F, flat washers, clearance hole, chamfer tolerances, thickness tolerances, flatness, coaxiality, ISO 286.