Overview
ISO 7226:1988 specifies the general dimensions and marking for hexagonal die nuts (hexagonal dies) used for hand threading. This second edition (1988) supersedes ISO 7226:1985 with a minor revision. The standard covers hexagonal die nuts for a range of thread systems: ISO metric (coarse and fine), ISO inch (UNC/UNF), pipe threads (series R and G), and non-preferred series (BSW, BSF, BA). It was prepared by ISO/TC 29 (Small tools).
Key topics and requirements
- Scope and applicability: Dimensional rules for hexagonal die nuts intended for manual threading, including groups of threaded diameters and corresponding dies.
- Dimensional tables: Two main tables define dimensional characteristics:
- Table 1 - Hexagonal die nuts for metric and inch threads (excluding tapered pipe series R).
- Table 2 - Hexagonal die nuts for tapered pipe threads, series R (gives approximate base diameters, pitch and cut length E).
- Length and profile parameters: Specifies machined (cut) lengths and related size groups; the standard notes permissible manufacturer options for certain minimum lengths.
- Marking requirements:
- Die nuts conforming to Table 1 must be marked with the thread designation as specified in ISO 2568.
- Die nuts conforming to Table 2 (series R) must be marked with the letter R immediately followed by the thread designation (example shown: "R 1/8").
- When tools fully conform to ISO, the ISO symbol may be added to the marking at the manufacturer’s discretion.
- References and related profiles: The standard references ISO thread and pipe standards (ISO 68, ISO 261, ISO 2568, ISO 7-1, ISO 228-1, etc.) for thread profiles and designations.
Applications
- Tool manufacturers: Designing and producing hexagonal die nuts to standardized dimensions for interchangeability.
- Fastener and tooling suppliers: Labelling and cataloguing dies that match customer thread specifications (metric, UNC/UNF, pipe threads, BSW/BSF/BA).
- Maintenance, repair and workshop technicians: Selecting correct hexagonal die nuts for on-site hand threading and thread repair.
- Quality and conformity assessment: Inspecting die nuts for compliance with standardized dimensions and marking for traceability.
Related standards
Keywords: ISO 7226, hexagonal die nuts, hexagonal dies, thread dies, ISO metric threads, UNC, UNF, pipe threads series R, BSW, BSF, BA, marking, dimensions, tolerances.
