Hole centering aid

[Toolmaker51]

There is merit in both versions; Marv's drills into a decreasing error, I've used it and it works.
Toolguy is correct as well, though I don't use a wiggler or edge finder. This is especially good on rough or not very symmetrical material. I use an endmill shank, dowel pin, any diameter works, being a decent round and straight is sufficient, long as part fits within boundaries of material. A DRO makes it easy.
As described, touch one side and note position or zero axis. Retract and traverse to opposite side without disturbing cross axis, draw up to contact and divide result by 2. Do other axis the same way.
This often avoids surface plate & height gauge work, where locating a scribe line remains subject to interpretation.

Marv mentioned 'aliquot' (which wasn't in microsoft spell check, lol), I recognized term but took wrong definition being a certain portion instead of any portion of a whole. So, went to look, satisfied at not being too far off.
But there was a totally foreign usage too; of interest to musicians in the house, "Aliquot stringing, in stringed instruments, the use of strings which are not struck to make a note, but which resonate sympathetically with struck notes ..." from wikipedia.