Tuner hole sizes: vintage 11/32 inch or modern 10mm?

Most tuner swaps go wrong in the same place: the hole in the headstock. Most guitars are drilled for one of two main systems, vintage or modern, and the tuners for one won't drop into the other. The good news is you can usually tell which you have in about ten seconds, without taking anything apart.

The short answer

• Vintage size: 11/32" (8.73mm). Kluson Deluxe and Gotoh SD91 style tuners with a press-in bushing.
• Modern size: 10mm. Sealed tuners held by a threaded bushing and hex nut on the front of the headstock, such as Grover's 102 series Rotomatics, Fender's two-pin tuners and Hipshot's standard tuners.

So if you searched for the hole size for Kluson Deluxe six-in-line tuners: StewMac lists them as needing an 11/32" (8.8mm) peghole, and Kluson's own replacement bushings for the Deluxe series have an 8.85mm outside diameter.

How to tell which you have

Look at the front of the headstock first, then the back. Hipshot's guide to peghole sizes gives the clearest way to tell them apart:

• Vintage (11/32"): a plain metal bushing pressed into the hole from the front, with no nut. On the back, each tuner is usually held by two small screws, and neighbouring tuners often share a screw.
• Modern (10mm): a hex nut and washer on the front. On the back, each tuner is held by one screw or by small locating pins.

Don't go by looks alone. Fender's ClassicGear tuners have the vintage look, with old-school safety posts, but they use Fender's modern two-pin mounting. Fender says they fit modern Fenders such as the American Professional II Stratocaster, American Professional II Telecaster, Player Stratocaster and Player Telecaster. Hipshot puts Fender's two-pin tuners in its 10mm group. Vintage-looking tuners on a guitar don't mean vintage-sized holes.

Why the numbers never quite match

If you've seen 8.5mm, 8.7mm and 8.8mm all quoted for the vintage size, you're not going mad. 11/32" works out at 8.73mm. Hipshot round it to 8.5mm, StewMac and Gotoh's retailers say 8.8mm. They all mean the same hole.

The modern size has the opposite problem. It's a metric 10mm hole, but makers convert it to inches differently: Hipshot and StewMac write 13/32" (which is really 10.32mm) and Grover writes 25/64" (really 9.92mm). If you're buying a reamer or drill bit, go by the 10mm figure, not the fraction.

The in-between holes

Not every vintage-style headstock is exactly 11/32". A few things to know before you buy:

• Stepped holes: Hipshot describe a vintage variant that's 11/32" at the front but narrows to 1/4" at the back. You can't see the step without taking a tuner out.
• Slightly larger vintage holes: Gotoh's SD91 Magnum Lock Trad sets come with two sizes of press-in bushing, 8.7mm and 9.2mm, so check which one your headstock takes.
• Fender's own vintage bushing: retailer listings for Fender part 0994946000 don't agree on its size, with figures from 0.345" to 0.363" (about 8.8mm to 9.2mm). If you're replacing bushings on a Fender, measure the old ones rather than trusting a listing.

How to measure your own

1. Take a photo of the back of the headstock before you unscrew anything.
2. Remove one tuner. On a vintage setup, ease the bushing out too.
3. Measure the hole at the front and the back with digital calipers. If they differ, you have a stepped hole.
4. Measure the tuner's string post. Kluson make adapter bushings in two bore sizes, 1/4" for their original US posts and 6mm for the metric posts they used from 1995 to 2006, so measure the post before you order conversion bushings.
5. Note the spacing between tuners and where the screws or pins sit. Hole size gets the post through, but these decide whether the tuner lines up.

Swapping between systems

• Vintage tuners in modern 10mm holes: no drilling for the posts. Conversion bushings fill the gap. Gotoh's SD91 retailers and Kluson both sell them separately. You may still need new screw holes on the back, because vintage tuners mount with screws rather than pins.
• Modern tuners in vintage 11/32" holes: the holes have to be opened up to 10mm. That's permanent, so it's a job for a tech or someone with a proper tapered reamer.
• Want to avoid new holes altogether? Hipshot's upgrade kits include their Universal Mount Plate, which Hipshot say means no modifications to the guitar. They make one kit for 10mm headstocks and a vintage kit for 11/32" holes (the vintage kit only fits a stepped hole if the 1/4" part is reamed out).

Hole size isn't the whole story

Getting the hole right is the first check, not the last. Six-in-line tuners also need to match your hole spacing: StewMac note that Kluson's plate-mounted six-in-line sets have different post spacing from the individual tuners used on Strats and Teles, so check the spacing before you order. Then there's the layout itself. Six-in-line and three-a-side sets are never interchangeable, and left-handed six-in-line guitars need a genuine left-handed set.

If you've got a Telecaster, our guide to what tuners fit a Fender Telecaster goes through each Tele we cover. For anything else, find your guitar to see the tuners we've matched to it, or get in touch.