On Fri, 24 Sep 2010 18:46:48 -0700, "Bill Noble"
wrote:



"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 -

They may not be Whitworth. I measured a tap I have here that's marked
1/2-12 USF and it's definitely a 60 degree thread. I've no idea what
USF stands for -- perhaps it's related to the old USS (United States
Standard) thread.

I repaired an old 36" bandsaw that used 1/2-12 fasteners and had to
single point several replacement bolts. The saw was probably late 19th
century. Old enough that the wheels had steel spokes and steam bent
oak rims.

--
Ned Simmons