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Got a set of tuners with splined press fit type bushings, outside diameter 10.75-10.78 mm
Fitting to a peghead of mahogany with an EIR overlay.
Does a 10.45 mm drill size sound about right?
That's around 0.012-0.013" less than the bushing OD.
Do I press them dry, or lube with a little water? Or maybe diluted fish glue?
(I intend pulling them in with a soft washer/nut/bolt)

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I usually drill a hole in a piece of scrap of similar wood to judge the fit . I press them in with an F body (Jorgensen pony) type clamp with
the soft plastic cauls that fit over the ends. Different woods seem to like different size holes.

If you plan on doing a lot of them StewMac has guided reamers in various sizes that work well. If not, drilling scrap to determine size is probably best.

I usually like to have them get tight with about 3/64-1/32 proud.

Here is a way to press them that works for me.

http://kennedyguitars.com/tuner-bushing-press.html

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I use a violin reamer to gradually enlarge the hole until the bushing starts to go in, and then press with a cam clamp. The taper means the highest pressure is at the bottom of the bushing, so it won't split the headplate.

I use a reamer too. I've bought the recommended Stew Mac reamer bits and found them to be too small, at least for the mandolin I was working on. Ended up just reaming them out anyway. I just use a C-Clamp and cork lined cauls to press them in.

Strong advocate of a tapered reamer to fit here. Most bushings are tapered to begin with, and even for those that are straight I strongly prefer to have a slightly tighter fit at the bottom where it can support more pressure, with slightly less pressure at the top where week or two in dry conditions can leave the surface and finish more susceptible to cracks.

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Eschew obfuscation, espouse elucidation.

Interestingly the makers seem to have had some PPPPP here - the (straight) splines don't start until about 1-1.5 mm down the bushing, but I was going to taper the top of the hole anyway, just in case they ever want pulling out.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Saw that some time ago Terence, just couldn't remember where.
Much the same as I plan on doing thanks to seeing it.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I actually remembered I made a video a few years ago. I found that the StewMac reamers if used in a hand drill were too loose because of the inescapable wobble, at least in my hands.

A drill press at lower speed was just a little tight sometimes but not bad. I cut off a hardware store plumber's reamer and got it to where it worked well for the final fitting and in conjunction with a #11 blade removing excess finish before final installation.

I over pressed a few at first causing cracks in the Nitro or in the case of a catalyzed finish causing a dent. I am really careful to just get it to touch the finish now.

https://youtu.be/Pm9wlrsH5M8

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It's not what you don't know that hurts you, it's what you do know that's wrong.