Acoustic Guitar Construction

I have a picture I took of a tuning machine from a Martin kit I got several years ago. I'm trying to determine the size hole to drill.
First, does Martin use fractional inches on their tuning machines or mm or even decimal inches?
The measurements I got with calipers is 25/64", 9.93mm, and .39 decimal inch. The part that screws in from the top is a bit smaller in diameter naturally. It's 19/64", 7.74mm, and .3045 dec inch.
Should I do it in steps? Bigger at the bottom?
Here's the picture.



OK, Don't pay the ransom, I made my escape. The smaller piece that screws in, is 19/64" because I have a bit that size and the ferrule (is that what it is) will screw in. I used a 3/8" bit on the body, and I have to put a good amount of pressure to have it go in. I used scrap cherry, and it would only go half way. So the search is on for a 25/64" bit either here or at Lowe's.

Now, the only remaining question: Would you do this in steps? The body is 5/16" tall, so I could run 19/64 thru the piece, and come thru the back with the 25/64 and go 5/16 deep. Is this overkill?

Much appreciated.
Bob

10 mm best to use a smaller drill first -- drill press recommended

Thanks, Ken, but would you do it in steps? Smaller bit for the ferrule, then the larger one for the body?
Bob

You know I read that pitch at SM -- I think its Gallop's idea to sell a special drill bit, ($85.00 !!!) "prevents the tuner from tipping" HUH? -- thing is I never heard of and for sure have never seen a tipped tuner even on cheap imports! My $.02 --- Poppy cock, actually the little illustration in the SM ad is kind of insulting and could not be more unrealistic.

However I do like the idea of a counter sink (pocket) for the washer to prevent chipping off the lacquer -- I do that sometimes.

The simple way I do it:

1. Mark the spots.
2. Drill with a drillpress a 2 mm bit though the entire head.
3. Drill a 100 mm bit from the back up to 4 mm from the top
4. Drill a 8 mm bit from the top.

And all with 1 dollar bits!

Thanks for all the inputs. I'm going with the 10 mm bit as soon as I can find the joker.
Ken, I wasn't sure what you were talking about, but I just went to their site and saw it. I concur. Sometimes it might be good to be a "belts and suspenders" guy, but sometimes it isn't needed. Dang that's expensive.
Bob