To this I would add, locate the hole lower on the post, where you've got the full diameter to work with. That'll increase the break angle over the nut, probably eliminating the need for a string tree. (I recently got some Wilkerson tuners that have two string holes; I put the high strings on the lower hole and skipped a string tree.) You can de-burr it afterward with some steel wool and/or fine sandpaper etc. I do this to cheap tuners anyway, just to eliminate any sharp edges to avoid string breaks.