This product is a 3/16" BSW (British Standard Whitworth) right‑hand split die manufactured from high speed steel for cutting, repairing and restoring Whitworth imperial threads. Its primary use is to form or re‑cut external BSW threads on bolts, studs and rod, or to clean up damaged threads during maintenance and restoration work.

The die is made from HSS (commonly supplied in M2 grade), offering superior hardness and wear resistance compared with carbon steel dies. The tool is supplied in the split die form, allowing a controlled amount of adjustment for light sizing or to compensate for wear; the split feature also aids in easing the die on and off a workpiece. The thread form is Whitworth (BSW) with the characteristic 55° thread flank angle and imperial pitch associated with the BSW series (used in British standard fasteners). This item is a right‑hand (RH) thread cutter and is intended for use in a compatible die stock (die holder) or power die holder; it has the conventional round/slotted die body rather than a hex head or keyed drive.

Typical applications include maintenance and refurbishment of classic cars, vintage machinery, steam engines, railway equipment, heritage restoration projects, general engineering workshops and wherever legacy BSW fasteners are used. It is suitable for cutting threads in mild steel, brass, aluminium and some non‑ferrous alloys when used with appropriate cutting lubricant and correct speed/technique.

Key benefits are the wear resistance and toughness provided by the HSS material, the adjustability and ease of use of the split die for precise thread fit, and direct compatibility with existing BSW fasteners and dies. Note that plain HSS has limited corrosion resistance compared with stainless products; use of protective oil or a coated die (TiN, black oxide) is recommended if exposure to moisture is a concern. For best results use a purpose‑made die stock and cutting oil.

Duchy Fasteners stocks this 3/16" BSW RH HSS split die individually and as part of tap-and-die assortments; we also carry die stocks, spare screws and a full range of imperial and Whitworth sizes in single items and multi‑pack sets.