Wiseman HSS BA Split Dies – British Association Right Hand Thread

Wiseman HSS BA Split Dies are manufactured from High Speed Steel (HSS) and designed for cutting new external BA (British Association) threads, as well as repairing, cleaning and restoring damaged or worn existing threads.

These round split dies feature an adjustable design, allowing minor adjustments to the thread fit when used with a suitable die stock. They are particularly useful for precision engineering, instrument making, model engineering, electrical equipment maintenance and restoration applications.

British Association threads feature a distinctive 47.5° thread profile with rounded crests and roots. Unlike conventional metric or imperial thread series, BA threads are identified by numbered sizes, with larger BA numbers representing smaller thread diameters.

BA threads were widely used in electrical equipment, scientific instruments, model engineering, small machinery and precision mechanical assemblies. They remain particularly relevant for maintaining and restoring older British equipment and components.

Designed for right-hand thread cutting, these split dies are suitable for producing and restoring BA threads on screws, studs, rods and other externally threaded components.

Key Features

• High Speed Steel (HSS) – Durable construction for reliable thread cutting and maintenance.

• BA Thread Form – Designed for British Association external threads.

• Right Hand Thread – Standard clockwise tightening thread direction.

• Adjustable Split Design – Allows minor adjustment of the thread fit when used with a suitable die stock.

• Round Die Construction – Designed for use with compatible die stocks and die holders.

• 47.5° Thread Profile – British Association thread form with rounded crests and roots.

• Numbered Thread Sizes – BA sizes are designated by numbers rather than nominal inch diameters.

• Thread Cutting & Restoration – Suitable for cutting new external threads and repairing existing threads.

• Precision Engineering Applications – Particularly useful for small threaded components and specialist restoration work.

Applications

Suitable for:

• Cutting new BA external threads on screws, rods and studs.

• Repairing damaged or worn British Association threads.

• Cleaning and restoring existing external threads.

• Model engineering and miniature machinery.

• Electrical equipment and instrument repairs.

• Scientific instrument manufacturing and maintenance.

• Vintage machinery and equipment restoration.

• Precision engineering and workshop machining.

• Manufacturing replacement screws and specialist threaded components.

Recommended Use

Select the correct BA split die size to match the required external thread. Each BA size has its own specified major diameter and thread pitch.

Secure the die in a compatible die stock or holder, ensuring the adjustment screws are correctly positioned. Prepare the workpiece to the appropriate diameter and apply a suitable chamfer to help the die start squarely.

Apply a suitable cutting lubricant and rotate the die clockwise to cut the thread. Periodically reverse the die slightly to break and clear chips where appropriate for the material and cutting conditions.

The adjustable split design allows minor adjustments to the thread fit. For accurate results, check the finished thread using a suitable BA thread gauge or correctly specified mating component.

Extra care should be taken when cutting smaller BA thread sizes due to the reduced diameter and increased risk of damaging delicate workpieces.

Important

• Suitable for BA (British Association) right-hand external threads only.

• Features a 47.5° thread profile with rounded crests and roots.

• BA thread sizes are numbered, with higher numbers representing smaller nominal diameters.

• Not interchangeable with metric, BSW, BSF, UNC, UNF or other thread forms.

• Adjustable round split die for cutting and restoring external threads.

• Requires a compatible die stock or die holder.

• Ensure the correct BA size is selected before use.