It depends on the parent material.
Stainless steels would be flo or dye penetrant. It will verify surface indications.
On carbon base steels magnetic particle inspection.
EDM surfaces will have a recast surface and depending on the amperage of the burn
Will result more or less recast.
If I do use EDM, I will request less than .0005-.001 per surface then remove it.
If EDM house gets agressive in the burn
It will result in more recast layer.
