Overview
ISO 235:2016 - Parallel shank jobber and stub series drills and Morse taper shank drills - defines standard dimensions and length specifications for common twist drills. The standard covers three drill types: parallel shank stub series, parallel shank jobber series, and Morse taper shank drills. For each type ISO 235:2016 provides three tables: dimensions in millimetres, dimensions in inches, and corresponding lengths set as functions of diameter steps.
Key topics and technical requirements
- Dimensional tables: Each drill type is specified by separate tables for metric dimensions, inch conversions, and length ranges by diameter step.
- Length specification: Corresponding lengths (cutting portion and overall lengths) are given as functions of diameter ranges (steps) to ensure consistent tooling selection.
- Tolerance on cutting diameter: The tolerance on the diameter of the cutting portion is standardized as h8 (metric basis) and converted directly into inches for inch-sized drills.
- Interchangeability: Metric and inch ranges are matched by subdividing diameters into steps derived from preferred number series; within a step the lengths and taper-shank dimensions are the same for both systems so that interchangeability is maximized.
- Default manufacturing details: Back taper is left at the manufacturer’s discretion; hand of cutting defaults to right unless specified otherwise; parallel shank drills are normally made without driving tenon.
- Morse taper details: Morse taper shank drills are included with their shank/taper dimensions and corresponding lengths (see relevant tables).
Applications and who uses this standard
ISO 235:2016 is practical for:
- Drill manufacturers and tooling designers - to standardize drill sizes, shank details and length series.
- Machine shops and production engineers - for selecting compatible drills (jobber, stub, Morse taper) and ensuring interchangeability between metric and inch tool inventories.
- Procurement and quality teams - to specify compliant drill tooling in purchase orders and inspection criteria using the h8 diameter tolerance.
- CAD/CAM and tooling libraries - to maintain standardized tool databases for programming and tool management.
Common use cases include selecting standard drill lengths for production runs, matching drill shanks to holders and spindles (Morse tapers), and ensuring consistent quality and fit across international suppliers.
Related standards
- Annex A of ISO 235:2016 maps designations in this document to the ISO 13399 family (cutting tool data representation), useful for integration with tooling data systems and digital tool catalogs.
Keywords: ISO 235:2016, parallel shank drills, jobber series, stub series, Morse taper shank drills, drill dimensions, drill lengths, tolerance h8, tooling standard, interchangeability.