I find it very helpful to reset the iron using my fingertip as a
guide to feel when the iron is moving , and how much.
Its amazing how sensitive your fingertips can be in judging motion.
Be aware of the wedge tip as you seat it against the iron, to make
sure it is remaining flat against the mortice.
Alternate back and forth gently between the two parts as you
sight down the profile to check the iron position.