Overview
EN ISO 4759-1:2000 - Tolerances for fasteners (Part 1) specifies dimensional and geometric tolerances for bolts, screws, studs and nuts with ISO metric threads and defines product grades A, B and C (A = most precise, C = least precise). It also covers tapping screws (grade A) and gives guidance on which tolerance systems and thread classes to use for design, manufacture and inspection of metric fasteners. Dimensions are in millimetres and tolerances apply to fasteners prior to coating unless otherwise stated.
Key topics and technical requirements
- Product grades A, B, C - defines tolerance levels for features (shank, bearing surface, other features) so users can select appropriate precision for application.
- Metric thread tolerances - thread tolerance classes (e.g., 6g, 8g) are referenced from ISO 965-3; notes on exceptions for certain products/coatings and higher property classes.
- Dimensional tolerances - shank diameter, thread length, head height/diameter, bearing face and washer-faced portions; tolerances are selected from ISO 286-1/2.
- Driving features - tolerances for hexagon flats, corners, sockets, slots, cross recesses and hexalobular recesses (with references to ISO 10664, ISO 4757).
- Geometrical tolerances - form, position and coaxiality rules per ISO 1101 and ISO 2692; tolerances of form and position are specified and illustrated.
- Tapping screws - tapping screw thread tolerances covered (product grade A) with reference to ISO 1478.
- Application rules - tolerances apply before plating/coating (see ISO 4042); product-specific standards take precedence over this part where differences exist.
- Informative annexes - examples of toleranced drawings, gauges and measuring devices to support implementation.
Practical applications and users
Who uses EN ISO 4759-1:2000:
- Fastener manufacturers and cold-forging shops - to set machining and forming tolerances.
- Design and mechanical engineers - to specify appropriate product grade and thread class on drawings for interchangeability and function.
- Quality/inspection engineers and metrology labs - to develop inspection plans, gauges and acceptance criteria.
- Procurement and standards committees - to write product standards, purchase specifications and ensure supplier compliance.
Practical benefits include consistent interchangeability, predictable fit and function, clearer drawings, and reduced assembly problems.
Related standards (normative references)
Keywords: EN ISO 4759-1:2000, tolerances for fasteners, bolts screws studs nuts, product grades A B C, metric threads, thread tolerance 6g, ISO 4759-1.