Originally Posted by bassbenj
How it attaches is important because if it's pressed in, too loose a hole is bad (falls out). And too tight is bad (can split headstock). If it is the type with a threaded bushing that just screws on then you are home free because it isn't much of an issue.
According to Stew Mac, they recommend an 11/16" hole for the Titans, because it gives a little room and its easier to find a drill bit this size than 21/32 or 0.656
Either way if you're making larger or new holes, this tuner should work with the 11/16" designation.
The Titans have two additional wood screws on the back-plate to keep the tuner in place vs the Schallers which are just set pins.
The mounting system for both these is banjo bolt or hollow screw, not a thrust washer which gets pressed in.
Schaller's M4S, (the Titan equivalent) are 17.00mm (0.669) which if you look at a conversion chart for 21/32 it will show 16.5mm, 16.66mm and 17mm as almost the same thing as 21/32. Yet at 17.00 mm its not really 11/16 as that in millimeters is 17.46 so both tuner brands of this model will be a little loose as well (not a press fit) but then once everything is tightened, it should work.
Its not exact at all, there is some play for either tuner.
Stew Mac's feeling is better a little loose than too tight.
Where the inconsistencies exist is in the classic bass tuners with the thrust washer like the Schaller BM, are 17.5mm, a tad over 11/16 hole, and 22.0 (55/64 or 0.866) thrust washer width, the Grover vintage 142 are 18.3 (23/32 or 0.718) for the thrust washer width, so yeah, there is no standard. You might want to make sure you measure before you make a choice on the thrust washer type, which should be based on the closest size and fitment to your original tuners, not just the brand, unless you want and have to do extra work.
Grover vintage 142:
Why the discrepancies is anyone's guess.
And then again, maybe not that critical.