Ivanising - gone wrong

[Decoke Dave]

How accurate does the the sizing of the holes need to be? I know nothing about Ivanising :o  but as an engineer I know it is impossible to sharpen a drill freehand to produce the original hole size.  It is easy to sharpen one to drill a hole but the cutting edges are never the same length, the result is the hole ends up bigger as the larger cutting edge rotates around the drill point.  You really do need a drill sharpening attachment to do it accurately.  Hopefully they are not that critical.