O2 sensor thread pitch and diameter

Good morning,
2000 pontiac gp se n/a 3.8l

does anyone know the thread pitch and thread dia the o2 sensors. i believe they are the same as an 18 mm spark plug thread. i want to make sure before i run a thread chaser to clean up the holes.

regards fish 96

http://i5.photobucket.com/albums/y186/lizzywiz/o2bung.jpg
18mm X 1.5mm