we bought some new taps for the bathroom and the sink ones went in fine
(apart from struggling to get some ptfe tape on the joints up underneath the
sink!). However when I came to put the bath taps in the nut on the water
pipes only goes a couple of turns up the taps thread before stopping (so the
pipe is loose). I dont want to force it and damage the threads, but what is
wrong here? The old taps are 8 years old, and look like the same 3/4" thread
when held next to the new one (pitch looks the same and thread profile
appears the same), but on both hot and cold the nut only goes up a couple of
turns. Any ideas before I trot off to the store tomorrow with tap in hand to
find something that will fit?

cheers

Dave.