"Grumpy" wrote in message
. au...
1/2"X 12 TPI is British Standard Whitworth.
I have no idea where you could find them in the U.S.
If you decide to turn them, note that the thread angle is 55 degrees not
60.


whitworth taps are commonly available - I happen to have some because of
british cars, but they are not at all hard to find - and ebay is a source
for them cheap -