Quote Originally Posted by NancysToy View Post
The brand may be Wentworth, but the standard is called Whitworth, developed by Joseph Whitworth in 1841. Also known as BSW, British Standard Whitworth.

http://en.wikipedia.org/wiki/British_Standard_Whitworth
Well, that clears everything up! So, Wentworth manufactures Whitworth spec tools but either way you're using Whitworth dimensions. Why would anyone be confused over that?