Quote Originally Posted by AgX View Post
Amongst the common metrical sizes the nearest fit [for a tool] would be M3 (3 x 0.5). Best fit concerning pitch but still seems a bit small concerning diameter.
Quote Originally Posted by Ian Grant View Post
I use an M4 x 0.7 tap on the Thornton Pickard release arms and that seems the best overall fit, I can use a size up or down because of the taper.

I just checked it.

Though the Standard M4 thread has a too steep pitch, due to the still small height of thread contact and the larger diameter of this contact this 4 x 0,7 size gave the best overall fit. At least for a provisional solution a DIY thread cutting attempt should be done.