This product is a 5/8-11 BSW HSS hex dienut, a hand and machine die designed to cut or restore external Whitworth threads on bolts, studs and bar stock. Its primary use is producing or refurbishing 5/8 inch diameter threads at 11 threads per inch in the British Standard Whitworth (BSW) form for right-hand fastening applications.

Manufactured from M2-grade high speed steel (HSS), the dienut offers the hardness and heat resistance required for repeated thread cutting. The BSW thread form uses a 55° thread angle and this dienut is ground to the correct profile for BSW; it is intended for producing external threads and is specified as right hand. The item is supplied in a hexagonal form so it can be driven by a suitable spanner or fitted into a compatible die stock for controlled application. No surface plating is normally applied to HSS cutting dies, but they may be supplied with a bright ground finish; black oxide versions are available by request for improved corrosion protection in storage.

Typical applications include engineering workshops, plant maintenance, classic vehicle restoration and heritage engineering where Whitworth threads remain in use. It is commonly used by automotive restorers working on British cars, by agricultural and railway maintenance teams, and in situations where original BSW fasteners need repair or replacement. The dienut is suitable for use on mild steel, cast iron and non-ferrous alloys when used with appropriate cutting oil and correct technique.

Key benefits include the wear resistance and hot hardness of M2 HSS which provides long tool life when cutting threads; accurate reproduction of the British Standard Whitworth thread form for compatibility with existing BSW fasteners; and the hexagon shape which allows positive wrenching or use in die holders. While HSS offers excellent cutting performance, users requiring higher corrosion resistance should consider alternative finishes or stainless options depending on the application.

Duchy Fasteners stocks a comprehensive range of dies and dienuts in imperial BSW sizes, available individually and in multi-packs. Please contact us for specific pack sizes and availability.