This is a 1/2" UNF HSS dienut, a hand-operated external thread die in a nut-style body used to cut, chase or repair 1/2"–20 UNF external threads on rods, studs and bolts. Its primary use is to restore damaged thread profiles or to produce fine-threaded external fasteners where Unified National Fine (UNF) form is required, typically during maintenance, machining or on-site repair work.

The cutting element is manufactured from M2 high speed steel (HSS) to provide good red hardness and wear resistance during repeated cutting operations. The internal thread form is 1/2" UNF (20 tpi) and is produced to the UNF thread profile as defined by ASME/ANSI B1.1, making it compatible with standard UNF fasteners. The dienut is presented in a round die body with a hexagonal outer profile so it can be used with a conventional die stock or simply turned with a spanner; the die has a chamfered lead to ease engagement with the workpiece. The tool is supplied with a light protective oil coating; it is uncoated HSS rather than stainless, so use of cutting fluid is recommended when working with stainless or abrasive materials and the tool should be stored dry to avoid surface rust.

Typical applications include automotive repair (engine studs, suspension components), engineering workshops, plant maintenance, fabrication and tooling shops where fine-pitch imperial threads are specified. The M2 HSS construction gives a long service life when cutting carbon steels, alloy steels and most non-ferrous metals; for hard stainless steels, slower feeds, appropriate cutting fluid and pecking are advised to preserve edge life.

Key benefits are the accurate UNF thread profile for interchangeability with standard fasteners, superior wear resistance compared with carbon steel dies due to the M2 HSS material, and ease of use in standard die stocks or with spanners thanks to the hex outer form. Corrosion resistance is limited (typical of HSS); protective oil and correct storage mitigate surface corrosion.

Duchy Fasteners stocks dienuts and dies across the common UNF size range and supplies single items or small packs for maintenance crews. If you need multiple sizes or a matched set, please contact us for availability and pack options.