Reviving this thread: I finally decided to swap tuners on my three MFC ukes. I bought Grover 6’s because they SHOULD just drop in and go, right? Not so fast. The first set went in the Fluke like a charm. The other two did not. The shafts are infinitesimally too big for the holes on the Flea and the Firefly. I’m baffled. I have a tapered reamer that could widen the holes from the outside of the headstock, but how could I get it to fit squarely to widen the holes from the inside? Any advice? I would hate to use a drill, because I’m afraid I’ll make a major mistake and ruin the neck.
You could try using a 1/4"
hex-drive step-bit, aka "UniBit' with a male-to-female 1/4" hex extension and put the step-bit cutting the hole from the INSIDE of the headstock and then you put the extension into that (via the opposing tuner hole), and then with a hex-driver (female) meant to accept hex screwdriver bits, cut the hole by hand, with a similar method to using a reamer.
(
Computer tool kits have these hex-driver handles as do many of the $5 multi-tip screwdriver kits from Lowes and Home Depot in the USA.)
Similar to what I showed here, which is actually
friction-fit and NOT hex on the UniBit nor the 'socket wrench' head I used (note: I hammered this together and it is nearly impossible to take apart without a bench vise):
I too would NOT use a drill.
Once you cut the hole wider, you will have very little wood on the face and back of the headstock and string tension on the tuner can tear the Fluke/Flea headstock in half over time because of the tension.
I had installed the Goto UPT-L tuners on my concert Flea, and that was a mistake because there was VERY little wood left on the front and back of the headstock after widening the hole from about 6mm to about 11mm. I have since removed the Gotoh tuners and replaced them with the Grover 9NB geared tuners (~$15 everywhere), hoping that the metal plate of the tuner serves to reinforce that part of the headstock.
This is not reversible really, nor is the Gotoh UPT-L tuner installation, but I refuse to be tormented by friction tuners and nowadays the PegHeds stick out too far to the side for my liking, for it makes the Fluke/Flea headstock look like the neck bolts on the Frankenstein monster to me.