Table:
text: British Standard Whitworth
List of thread sizes
Whitworth thread sizes
Whitworth_size_in Core_diameter_in Threads_per_inch Pitch_in Tapping_drill_size_
9/16 0.4558 12 0.0833 12.1 mm (0.4764 in)
5/8 0.5086 11 0.0909 13.5 mm (0.5315 in)
11/16 0.5711 11 0.0909 15 mm (0.5906 in)
3/4 0.6219 10 0.1 16.27 mm (0.6406 in)
13/16 0.6845 10 0.1 18 mm (0.7087 in)
7/8 0.7327 9 0.1111 19.25 mm (0.7579 in)
15/16 0.7953 9 0.1111 20.75 mm (0.8169 in)
1 0.8399 8 0.125 22 mm (0.8661 in)
1 1/8 0.9420 7 0.1429 
1 1/4 1.0670 7 0.1429 
1 1/2 1.2866 6 0.1667 
1 3/4 1.4939 5 0.2 
2 1.7154 4.5 0.2222 
2 1/2 2.180 4 0.250

Question: How many threads per inch of a 9/16 is in a British Standard Whitworth?

Question: Which Whitworth size is the only one with 5 threads per inch under British Standard Whitworth?