ISO 2540:2016

Overview

ISO 2540:2016 specifies standardized centre drills for centre holes with protecting chamfer - Type B. The second edition defines the metric dimensions, designation method and tolerances for these centre drills, and clarifies manufacturing options such as straight or spiral flutes. Unless stated otherwise, drills are right‑hand cutting. Annex A provides normative recommended dimensions for the corresponding centre holes (Type B), and Annex B maps designations to ISO 13399 tool data symbols for digital exchange.

Key topics and requirements

• Scope and metric basis: Only metric dimensions are covered and are the recommended sizes for future use.
• Dimension tables: Table 1 lists pilot diameters (examples: 1, 1.25, 1.6, 2, 2.5, 3.15, 4, 5, 6.3, 8, 10 mm), shank diameters, lengths and tolerance classes. Sizes shown in brackets are marked to be avoided when possible.
• Designation: Centre drills are designated by type, pilot diameter and shank diameter (example: B 2,5/10).
• Manufacturing options: Flutes may be straight or spiral at manufacturer option; default cutting direction is right‑hand.
• Tolerances and fit: The standard specifies tolerance classes for key dimensions (pilot, shank, etc.) to ensure interchangeability and correct seating in workholding.
• Annex A (normative): Gives two equivalent methods for selecting and dimensioning centre holes for Type B; includes reference values for minimum centre hole depths related to drill length.
• Annex B (informative): Provides a relationship between ISO 2540 designations and ISO 13399 symbols to support tool data representation and exchange.

Applications and users

• Who uses ISO 2540:2016: tool manufacturers, cutting‑tool designers, CNC programmers, machinists, production engineers, inspection and quality teams, and procurement specialists specifying standard centre drills and replacement tooling.
• Practical uses:
  • Producing and re‑sharpening centre drills to ensure consistent centre hole geometry and protecting chamfers for turning and lathe operations.
  • Specifying centre drills in tooling lists and Bills of Materials (BOMs) for manufacturing lines.
  • Ensuring compatibility with workholding systems and centres where correct pilot and shank dimensions affect concentricity and runout.
  • Integrating tool data into CAM/CAD and tool management systems using ISO 13399 mappings.

Related standards

• ISO 866 - Centre drills for centre holes without protecting chamfers (Type A)
• ISO 2541 - Centre drills for centre holes with radius form (Type R)
• ISO 13399 - Cutting tool data representation and exchange (all parts)

Keywords: ISO 2540:2016, centre drills Type B, protecting chamfer, centre hole dimensions, metric centre drills, machining standards, cutting tool standard.