Overview
ISO 4231:2016 - "Hand- and machine-operated circular screwing dies for parallel pipe threads - G series" - is an international standard that specifies the dimensional and marking requirements for circular screwing dies used to produce G series parallel pipe threads (in accordance with ISO 228-1). Published as the third edition (2016), this document is a supplement to ISO 2568 and ISO 4230, aligning general die geometry so hand-operated dies can be driven using the die stocks defined in ISO 2568.
Key topics and requirements
- Scope and applicability: Defines dimensions for both hand- and machine-operated circular screwing dies intended to produce G‑series parallel pipe threads.
- Dimensions: General dimensions (diameter, thickness, fixing features) are specified and illustrated (Figure 1) and tabulated in Table 1. Table 1 lists thread designations (from 1/16 up to 2 1/4 in), basic diameters, pitch and die body dimensions (D, E, C, b, a) in millimetres.
- Tolerances:
- Precision screwing dies: tolerances on D (f10) and E (js12).
- Non-precision screwing dies: tolerances are left to the manufacturer’s discretion.
- Marking: Dies must be marked with the letter G immediately followed by the thread designation (example: “G 3/8”). Where fully compliant, manufacturers may append the ISO symbol.
- Manufacturer discretion: The standard leaves certain shape details (e.g., V-groove shape, clearance holes) to the manufacturer’s design choices.
- Data mapping: Annex A provides a relationship between this standard’s designations and preferred symbols from ISO 13399 (cutting tool data exchange).
Applications and users
ISO 4231:2016 is directly relevant to:
- Tool manufacturers designing and producing hand- and machine-operated circular screwing dies for G series threads.
- Machinists and maintenance technicians performing thread cutting, repair and rethreading operations on pipes and fittings.
- Procurement and quality engineers specifying compliant dies for production lines or maintenance inventories.
- Standards bodies and CAD/CAM data integrators mapping die properties to ISO 13399 for data exchange.
Typical applications include production and on-site repair of parallel pipe threads in plumbing, HVAC, hydraulic systems, and general mechanical assemblies where pressure-tight joints are not made on the threads.
Related standards
- ISO 228-1 - Pipe threads where pressure-tight joints are not made on the threads (dimensions and designation)
- ISO 2568 - Hand- and machine-operated circular screwing dies and hand-operated die stocks
- ISO 4230 - Circular screwing dies for taper pipe threads - R series
- ISO 13399 - Cutting tool data representation and exchange
Keywords: ISO 4231:2016, circular screwing dies, parallel pipe threads, G series, ISO 228-1, die dimensions, marking, tolerances, ISO 2568.
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