[Lynn Eades]

As Kevin has said, A standard track pin is 7/16" = 0.4375" = 11.11mm.
For most of you, to fit new pins made of 4140 at 7/16 dia. that is probably as good as it gets.
If your track is that worn that an oversize pin is needed, its probably too dangerous to use, as you risk the breakage of the link.
Think for a moment about what happens when you loose a track at speed, or on a steep hill.