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I bought some Grover open-back 18:1 tuners from John Hall and am about to drill for the first set I am using. I checked both the Grover site and Stew Mac, and both specify 11/32" post (not bushing) holes. I found this a little confusing as I have used similar Grover ukelele tuners and drilled 1/4" holes for them, and then used the SM pilot reamer to open the holes for the bushings (which works great). So I checked the post diameter on the tuners (before going to the nearest Lee Valley to buy an excellent but expensive 11/32" lipped brad point bit). The post is 0.247" - just under 1/4". When I re-read both web sites, I can see that they are referring to the hole diameter for the bushings. So is it considered acceptable or advisable to drill 11/32" post holes all the way through for 1/4" posts? Or do they assume we will drill 1/4" for the posts, and ream for the bushings some other way? I have the correct SM reamer for these tuners so will do that, but it seems a little confusing to me. Bruce W.

do a test hole for the ferrule first then use that to center your 1/4 in for the post

What John said. I installed my bushings first, and then letting the posts float in the bushings, drilled for each tuner's mounting screws, assuring myself that the tuner post had free movement in the bushings. I DID NOT drill for mounting screws first and attempt to get the bushing to agree.

I should have been more clear in my first post. My question is, do people drill one 11/32" hole all the way through for the tuner post and bushing, or do they drill a 1/4" hole for the post, and drill or ream the top portion only to 11/32" for the bushing?

If you're just looking for reports of how other people do it, or would do it, here's how I'd probably do it.
From the top, drill 11/32" dia. 0.315" deep,
Press in the bushing,
Drill through the bushing and the rest of the headstock thickness with a "D" size drill (0.246"),
Try tuner for fit. If the D size hole is too tight, enlarge to .250".

If you have a drill press and can clamp the headstock so it doesn''t move, you can omit the drill-through-the-bushing part and drill 0.250" after drilling 11/32" 0.315" deep.