I'm installing a new lockset on the main entry door of the house. I need to drill 2 new through holes, one for a mounting screw and one for the interior turnpiece. I'm changing out an old Baldwin piece for a new one.

Question is how to ensure I drill the hole square/perpedicular to the door. I prefer to drill the hole with the door on its hinges, because the beast is solid mahogany and it ain't light.

Am I making much ado about nothing? On one hand I want the holes to be perfectly square to the door surface. On the other hand, no one will see the holes, and if I mess up a little bit, I can make them a tad bigger and it really won't matter as far as I can see.

Another question on which drill bit to use. One hole is 5/16" and the other is 5/8". Which bit is best for this - forstner, spade or regular twist drill? Thanks.