This is an 8 mm × 1.25 HSS dienut, a hand-operated cutting nut used to cut or repair external metric threads on studs, bolts and round bar. The primary use is to restore damaged threads or to form new M8×1.25 external threads quickly on-site or in the workshop without the need for a full die set.

The dienut is manufactured from high speed steel (HSS), typically M2 grade, heat treated and ground to provide a durable cutting edge and good wear resistance. The tool produces the ISO metric thread profile (ISO 68‑1) with a pitch of 1.25 mm and is suitable for standard ISO/DIN/BS metric threads (reference: ISO 261, ISO 965, DIN 13 and BS 3643). The internal profile is sized to cut to the M8 × 1.25 specification; the external flats are machined to suit standard spanners so the dienut can be driven by hand or with a short wrench where access is restricted. No drive recess is required because the outer hex is used to apply torque.

Typical applications include maintenance and repair work in automotive workshops, machinery overhaul, fabrication and general engineering where damaged studs and bolts must be quickly re-threaded. The M2 HSS construction makes the dienut suited to cutting mild steel, cast iron, aluminium, brass and many non‑ferrous alloys; it will also cut stainless steels with appropriate cutting fluid and slower feed rates. Because the HSS material retains hardness at elevated temperatures, it remains sharp longer than carbon steel equivalents and is better for repeated use.

Key benefits are long cutter life and edge retention from the HSS material, accurate ISO‑conforming thread form for interchangeability, and straightforward compatibility with standard spanners and die‑holders. As HSS is not stainless, users should protect the tool from corrosion by light oiling after use; some finishes such as black oxide are available to improve rust resistance where required.

Duchy Fasteners stocks a comprehensive range of dienuts and dies, available in a wide selection of metric sizes and pitches, supplied individually or in multi‑pack sets to suit workshop and field service needs. If you require alternative finishes or matched die sets, please contact our sales team.