Parallel (straight) thread, British Standard Pipe Parallel thread BSP; originally also known as British Standard Pipe Fitting thread/BSPF which have a constant diameter. For producing precision threads by hand tapping, for starting threads - either second or bottoming taps should used after to achieve desire thread depth.
General purpose use
Through & blind holes
Suitable for both hand and machine operations
Threads per inch 14
Drill diameter 24.5mm