17/32 wrench?

[AVB]

I think you have that backwards Trav.

Using the example of the 5/8 wrenches pictured the 5/8 whitworth bolt would be the same diameter as a 5/8" STD bolt.

Unless I am missing something it looks like the Whitworth wrenches are classified by the actual bolt size where as STD wrenches go by the hex size. A 5/8" SAE bolt takes a 15/16" wrench and a 5/8" wrench fits a 7/16" bolt.

From that wrench size table chart you posted it looks like the 1/4 Whitworth fits a .525" hex not a .525" bolt.

 

[Trav]

But then you would have a 1/4-20 bolt with a 13.5mm (approx) hex head. That would seem to be to be a bit on the large side don't you think?
I still have a set of Whitworth and i can tell you they are some strange sizes in relation to the actual bolt diameter.

 

[AVB]

I thought that was the whole deal with Whitworth fasteners, I personally have no experience with them. That is not really too big of a difference from a STD 1/4"-20 with a 7/16 or 11.11mm hex.