Dan,
They are M14 fine (x1.5 I think).
The set screws are often hardened so may be brittle. I have slipped a piece of tube over mine before & have also used a socket over the nut & then heaved on an extension bar plugged into the socket.
Originally though, when I first got it, I had to remove the springs & inserted a rod/pole & whacked that back & forth many times to fully release the hold that the original dimples had.
As, I think, Clem said on your other post.
When this is all done, do not over tighten the lock nuts on the adjusters. The hardened screws can fatigue if they are over stressed - causing them to break. Your front end will then drop suddenly. Ask me how I know!
Phil.