Overview
ISO 2901:2016 - ISO metric trapezoidal screw threads - Basic and design profiles defines the geometric basic and design profiles for ISO metric trapezoidal screw threads. It is chiefly applicable to traversing threads used for linear motion on machines and tools (leadscrews, jacks, vises), but the profiles can also be used for fastening threads. The standard replaces earlier editions and gives the formal symbols, profile geometry, dimensional formulae and reference tables needed for design and manufacture.
Key topics and technical requirements
- Scope and terminology: Uses definitions from ISO 5408 (Screw threads - Vocabulary) and specifies symbols for major/minor/pitch/pitch diameter (D, d, P, etc.).
- Basic profile: A common reference profile for internal and external threads; key geometric relations are provided (e.g., H = P/(2·tan15°) ≈ 1.866025404·P; flat width w ≈ 0.366·P) and a table of basic profile dimensions by pitch.
- Design profiles: Separate design profiles for internal and external threads with clearances, crest/root radii and heights defined. The standard gives values for parameters (a, c, h, R) by pitch in a design-profile table.
- Manufacturing notes: Allows controlled modifications for rolling (e.g., larger root rounding; external-thread minor diameter may be reduced by up to 0.15·P) - such changes must be agreed between customer and manufacturer.
- Tolerancing relationship: Design profiles are the basis for applying limit deviations; tolerances for maximum-material conditions are handled in related tolerancing documents.
Applications and who uses it
ISO 2901 is essential for:
- Mechanical and design engineers specifying leadscrews, linear actuators, machine tool feed systems and jacks.
- Fastener and screw manufacturers who produce trapezoidal threads by cutting or rolling.
- Quality, inspection and metrology teams verifying thread geometry and conformity.
- Procurement and specification writers creating technical drawings, part specifications and supplier agreements.
Practical benefits:
- Ensures interchangeability and consistent performance of traversing threads.
- Provides standard geometry for strength, wear, and manufacturability (including rolling).
- Simplifies communication between designers and manufacturers through standardized symbols and tables.
Related standards
- ISO 5408 - Screw threads: vocabulary (normative reference for terms)
- Tolerancing standards (e.g., ISO 2903 historically referenced for thread tolerances) - consult latest ISO documents for tolerances and limit deviations.
Keywords: ISO 2901, ISO metric trapezoidal screw threads, trapezoidal threads, design profile, basic profile, leadscrew standard, thread geometry, machine screw threads.
