Overview
ISO 1478:1999 defines the thread form and thread ends for tapping screws (sheet metal screws). This International Standard - prepared by ISO/TC 2 (Fasteners) - covers tapping screw thread sizes ST1,5 to ST9,5 inclusive and provides dimensional limits, pitches and end-type requirements intended for consistent manufacture and interchangeability.
Key Topics
- Scope: Thread geometry and thread-end forms for tapping screws (sheet metal screws) sized ST1,5 → ST9,5.
- Dimensions and tolerances: Detailed thread pitches, maximum and minimum diameters, and reference dimensions are provided in the standard’s Table 1 and associated figures. These establish acceptable size ranges for manufacturing and inspection.
- Thread ends: Specifies permitted end types (notably Type C cone end, Type F, and Type R) and requirements for points:
- Type C: No extrusion of excess metal beyond the apex resulting from thread rolling; a slight rounding or truncation of the point is desirable.
- General note: ends should not be sharp to the touch; some rounding is acceptable.
- Incomplete thread length: Reference lengths for incomplete threads (thread run-out) are included.
- Designation: The standard gives the format for naming a tapping screw thread (example: “Tapping screw thread ISO 1478 - ST3,5”). Product standards may require the thread-end type to be specified in product designations.
Applications
ISO 1478 is used wherever consistent tapping screw threads are required:
- Manufacturers of sheet metal screws and fasteners - for tooling, thread rolling and quality control.
- Design and product engineers specifying sheet metal fastenings in electronics, appliance, automotive and construction assemblies.
- Quality inspectors and testing labs - to verify thread geometry and end conditions against standardized limits.
- Procurement and standards managers - to ensure purchased tapping screws meet internationally recognized dimensions and interchangeability criteria.
Using ISO 1478 helps reduce assembly problems (poor fit, cross-threading, point damage) and ensures compatibility across suppliers.
Related Standards
- Prepared by ISO/TC 2 (Fasteners); users should reference relevant product standards for tapping screw materials, mechanical properties and head types. For complete fastening system requirements, combine ISO 1478 thread specifications with applicable product and material standards.
Keywords: ISO 1478, tapping screws, sheet metal screws, thread dimensions, thread ends, ST1.5, ST9.5, fastener standards.
