This product is a 1/4" UNF, right-hand split round die designed to cut or restore Unified National Fine (UNF) threads — typically 1/4"-28 TPI — on shafts and studs. Its primary use is for producing new UNF threads or repairing damaged threads in maintenance, engineering and assembly tasks where fine-pitch threads are required for higher clamp-up precision and vibration resistance.

The die is manufactured from M2 high speed steel (HSS), offering the toughness and red‑hardness needed for repeated cutting operations. The cutting faces are ground and the body is finished with a protective black oxide to give some corrosion resistance and reduce light surface rust; as with all carbon and HSS tools, use of cutting fluid is recommended when working with hard or stainless materials. The die is a split type with an adjustment screw, allowing a small degree of size fine‑tuning for thread fit and for easing removal from stuck workpieces. It is a standard round die intended for use in a compatible die stock (holder) rather than a powered die head.

The thread form conforms to the Unified thread profile as defined in ANSI/ASME B1.1 (Unified Inch Screw Threads), making the threads produced compatible with common UNF fasteners used across UK and international supply chains. Typical materials machined with this die include mild steel, aluminium alloys, brass and some stainless steels (appropriate lubrication and slower feeds advised). Industries that commonly use 1/4" UNF split dies include automotive repair and restoration, general engineering workshops, maintenance and repair operations, and prototyping where imperial fasteners remain in use.

Key benefits of this split HSS die include long tool life under correct cutting conditions, the ability to fine‑adjust thread fit for interference or running fits, good wear resistance from the M2 HSS material, and compatibility with standard 1/4"-28 UNF fasteners. The black oxide finish provides modest corrosion protection but the die is not stainless; store dry and apply light oil for longer life.

Duchy Fasteners stocks a comprehensive range of hand and machine dies and die sets in imperial and metric sizes; this 1/4" UNF split die is available singly and in boxed sets, and we can supply in various pack quantities to suit workshop and trade requirements.