This is a 20 mm x 2.5 HSS dienut: a solid round die for cutting or repairing external ISO metric threads on rods, studs and shafts. Its primary use is to form or restore M20 × 2.5 threads (ISO metric coarse series) on components where a new or renewed external thread is required, typically used with a compatible die stock or holder and appropriate cutting lubricant.

The die is manufactured from high speed steel (commonly M2 HSS), heat-treated to retain a keen cutting edge and good wear resistance. The thread produced conforms to the ISO metric thread form and is compatible with DIN/ISO/BS metric standards such as ISO 261/965 and BS 3643 for general thread dimensions and tolerances. The nominal size is 20 mm with a 2.5 mm pitch (M20 x 2.5). The die is supplied with a standard round die profile and is intended for use with right-hand threads; it is suitable for manual use in a hand die stock and in some machine holders where specified.

Typical applications include mechanical maintenance, plant and machinery repair, fabrication workshops, automotive and agricultural servicing, rail and marine maintenance, and general engineering. The HSS material and heat-treatment make the dienut effective on mild and medium carbon steels, alloy steels and non-ferrous metals; for stainless steels and harder materials use slow feeds, correct lubrication and multiple light passes to avoid premature wear.

Key benefits are the durable cutting edge of HSS for long life and consistent thread form, dimensional compatibility with ISO/DIN/BS metric fasteners, and a protective finish (black oxide or similar) that offers modest corrosion resistance during storage and use. The solid die design delivers accurate thread profiles and is easy to seat and align in standard holders, making it suitable for both one-off repairs and repetitive workshop work.

Duchy Fasteners stocks a comprehensive range of metric dies and dienuts in sizes covering common workshop needs, available individually or in packs and sets. If you require alternative pitches or thread forms we can supply matching taps, die stocks and holders.