You're right, Andy. It's BSF, not BSW. The chart I was looking at had two
charts on the page for Whitworth threads, and 7/16 x 18 was on the lower
(BSF) chart. Nevertheless, BSF is still a Whitworth thread form. I'm still
looking for a tap to borrow :-)

--
Bob (Chief Pilot, White Knuckle Airways)


"Andy Dingley" wrote in message
...
On Mon, 21 Nov 2005 09:11:05 -0500, "Bob Chilcoat"
wrote:

7/16 x 18 is BSF, not BSW Whit is 14 pitch.

I've a couple of Whitworth plug taps here and it wouldn't matter if one
met a grinder and ended up tapered. Still trying to find some BSF
though.