This product is a 1/4" BSPF (outer diameter 1 5/16") right‑hand split die made from high speed steel (HSS) for cutting or repairing external BSP (British Standard Pipe) threads. Its primary use is to cut standard BSP external threads on rod, bar or pipe end preparations, and to restore damaged threads on fittings where a parallel (BSPP/BSPF) Whitworth‑form thread is required.

The die is manufactured from M2 grade high speed steel and is ground and heat‑treated to provide durable cutting edges suitable for hand and light machine use. It carries a black oxide finish to reduce glare and provide light corrosion resistance; as with all HSS cutting tools, appropriate cutting oil is recommended during use to extend tool life. The thread form is the Whitworth 55° profile commonly used on BSP threads and is intended to conform with the BSP thread family as defined in ISO 228‑1 for parallel pipe threads (and in the context of pipe fittings where tapered threads are referenced, to ISO 7‑1/BS EN 10226). This is a right‑hand (RH) die supplied in a split design to allow slight adjustment of the cut and easy removal from the workpiece.

Typical applications include plumbing and pipework assembly, instrumentation and hydraulic fittings, maintenance and repair in HVAC, marine and general engineering workshops, and production environments where BSP parallel threads are used. The split construction makes it particularly useful for rethreading damaged parts and producing repeatable threads with controlled fit where a close tolerance BSPF thread is required.

Key benefits are the wear resistance and edge stability of M2 HSS compared with carbon steels, the adjustability and ease of chip clearance provided by the split die, and compatibility with the broad range of BSP fittings and nuts that utilise the Whitworth 55° form. The black oxide finish offers basic corrosion protection in storage and service; normal cutting lubricants will improve finish and extend life.

Duchy Fasteners stocks this die in single items and in multi‑pack options, and carries a comprehensive range of BSPF sizes and complementary die stocks and holders to suit hand and machine tapping applications. If you need alternative sizes or complete sets please contact us for availability.