Can anyone help me to identify a plumbing thread?
Here's a photo, the scale below is in mm:
Pipe diameter is 0.51" (13mm), a 29/64" (11.5mm) drill bit is a loose fit in the female fitting, a 15/32" (11.9mm) bit doesn't fit.
TPI: roughly 6 turns in 8mm (from photo) is 19 TPI.
Any thoughts?
Nigel