Given the 1 post count, this is probably a troll, but in case others read this, you almost certainly do NOT have a Whitworth thread on your bike or bike part unless you have a Raleigh (or other Brit bike) from the 70s. Given the Brit's reputation for mechanical peculiarity, Whitworth MIGHT appear* on some parts offered today, but I doubt very many.

In any case, retapping threads because you can't find the right size fastener is poor practice: you weaken the fastened joint considerably. If anyone is considering this, consult your LBS or post a question here.

*The Brits have some justification for this pride in British engineering. For example the Rolls Royce Merlin 66 engine. Plus, Sir Joseph's (Joseph Whitworth) thread spec did deliver fasteners that are probably superior to most standard flat root and crest UN bolts. And it was from the mid-1800s!