How to Shrink a Hole

How to Shrink a Hole

A while back, I wrote about some methods for enlarging holes — for instance, if you wanted to fit larger tuners or a larger control pot into a hole that had housed something smaller.

But what if you want to go the other way? What if you want to remove some hardware that’s bigger than the stuff being installed?

Why do Gibson headstocks break?

Why do Gibson headstocks break?

There's a big chunk of my income that comes from repairing broken necks and headstocks. And, by far the biggest chunk of that comes from repairing the broken necks and headstocks of Gibson guitars. 

So what is it that makes Gibsons more prone to lose their heads?

Locking Nut String Retainer Bar Adjustment

Locking Nut String Retainer Bar Adjustment

You know the string retainer bar? Also known as the ‘dammit-I-forgot-to-put-the-string-under-it bar’. 
It’s that little thing on the headstock, between your nut and tuners. The strings install under it. 

You’ll find them most often on guitars with locking tremolo systems like Floyd Rose and Ibanez Edge bridges, and, on these instruments, it's important that it's properly adjusted.

String break-angle at nut - A Primer

String break-angle at nut - A Primer

So, I want to talk about a few tips related to string ‘break angle’ — the angle the string takes over the nut or saddle. However, I reckon that it might be useful to explain what I mean and to give a little background on this area first. 

Let's start with the break angle at the nut — that's the angle at which the string leaves the nut and heads for the tuner.

Fender Bi-Flex Truss Rod Nut Repair

Whenever I talk about adjusting Fender guitar truss rods, I try to emphasise the importance of the correct size allen wrench.

Now, this applies to any truss rod that uses a hex-socket for adjustment but especially—really super especially to those guitars with the Fender Bi-Flex truss rod. You know the one—it’s adjustment nut is hidden away beneath a wooden (walnut) dowel and you access it via a narrow hole at the headstock.

Fender use a ⅛” allen wrench to adjust these. Problem is, that’s a relatively small wrench and the ‘flat’ surfaces of the wrench and socket aren’t huge. It’s annoyingly easy to ‘wear’ these flat surfaces so that a wrench no longer grips it.

Allen wrenches that don't fit snuggly, or are themselves a little worn, can wear down your hex edges and leave you with a ruined truss rod nut.

Worn Fender Truss Rod Nuts

Truss rod nuts can become worn. And then they don't work. This applies especially to the adjustment nuts Fender hide away behind a wooden plug at the headstock.

You can see what happens in the illustration above. Let’s face it, a circular socket isn’t the most useful thing when it comes to turning a nut.

When this happens, you end up with a truss rod that can’t be adjusted. That’s less than ideal when you’re trying to properly set up an instrument.

Removing Bi-Flex Truss Rod Nuts

It’s possible to remove that walnut plug and to replace the nut. It’s not super difficult but you do need to be careful because, hot!

Yep, we use heat to soften the glue holding the plug in place. Then we can remove it.

Here’s how:

Steps For Fender Truss Rod Nut Replacement

First off, strip the headstock hardware. Remove the tuners and string trees. Do this so you can get easy access to the plug. Otherwise, you’re trying to work at an angle and that’s a recipe for burning stuff. Next up, use a sharp knife (Exacto-type) to score the finish around the plug.

Truss rod wooden plug on Fender guitar. Score around the edge with a sharp knife before removing. 

Protect the face of the headstock. I just wrap some foil around it a couple of times.

I use a soldering iron. The bit fits into the hole in the walnut plug. Be careful if you’re doing this. I find that it’s not necessary to make contact—the soldering iron doesn’t need to touch the wood.

Use a soldering iron to heat the walnut plug concealing the Fender truss rod nut. You don't need to actually touch the wood.

This is tricky so be careful. The heat from the iron will penetrate through the walnut and soften the glue. It should be ok if the iron taps off the walls of the hole occasionally, but don’t let it remain in contact or the wood will scorch.

It doesn’t usually take too long for the glue to soften. Insert an allen wrench and ‘loosen’ the nut. Turn it counter-clockwise and the nut will eventually butt against the inside of the plug. If the glue’s soft enough, the nut will push it out*.

*A quick note on this: This is very good reason to remove a nut that’s worn before it goes too far. Stew Mac’s Gripper wrenches (see below) can help but sometimes you end up with a completely worn nut and you have to get the plug out by more invasive means.

Backing out the truss rod nut will push the plug out (assuming the glue's sufficiently softened of course). 

Eventually the nut will reach the end of the truss rod but, by then, the plug should protrude enough to grab. 

When the plug protrudes enough, you can grab it with a needle-nosed pliers and pull it out. Be careful—it’s easy to crush or break the plug at this point.

Behind the plug is a washer (keep it).

Behind that is the nut. Fish it out.

The washer sits between the Fender truss rod nut and the (now removed) wooden plug

Here's how they install: Truss Rod Nut - Washer - Walnut Headstock Plug

New truss rod nut time. On the American Standard, the nuts have a ⅛” hex socket and a 10/32 thread. Lubricate the threads of the new nut with a little (I mean a little) Vaseline and screw it back in. Don’t forget the washer next and follow up by reinserting the plug with a smear of glue.

Depending on the guitar, I’ll sometimes do some finish touch-up.

Help Prevent Worn Truss Rods

  • The fact that the adjustment nut is buried an inch deep means that it can be awkward to reach. Sometimes the short leg of your allen wrench won’t reach and you have to use the ‘ball’ end. This makes it harder to get good, deep purchase into the hex socket (and to get decent leverage to actually turn it). Check your guitar stores for a special allen wrench, made with a longer leg, especially for this job.
  • Stew Mac offers a ‘Gripper’ wrench. This has a hex head that tapers—it gets wider along its length. The idea is that, as it’s inserted, the wider part might be enough to grip the socket. 
    This is pretty handy but, if your adjustment nut has started to wear enough that a standard wrench won’t grip, I’d really recommend replacing it. Use the Gripper wrench to remove the nut and install a new one. Otherwise, you risk wearing the nut to the point where even the Gripper won’t work.
  • It should be obvious, but don’t force a truss rod. If it’s not adjusting easily, stop and regroup. Try slackening off the strings. If that doesn’t work, you could try forcing the neck into a slight back-bow—using clamps and a brace (second part of this article)—and just tightening the rod to hold it (the rod’s not doing the work to get there). The Rickenbacker Truss Rod Trick can also help.

Let me just repeat, don’t force anything. Check with your trusted repair person if you have any doubts. Remember, this can happen to any truss rod nut—not just ⅛” nuts, not just Fender, and not just hex/allen nuts. I've had to cut rounded Gibson nuts off because people didn't use the right tools too. Be careful. 

Guitar Headstock Repairs with Rubber Bands

There's a lot you can do with a bit of wire, a luggage ratchet-strap, and a big rubber band. 

In some cases, the best way to repair a guitar headstock doesn't involve clamps and cauls. Depends on the particular damage but this one doesn't need anything more 'specialist'. 

Repairing the headstock crack on this Gibson guitar doesn't call for lots of clamps and cauls

Some breaks are much easier and 'sounder' to repair using straps and some rubber bands.

Now, I should mention that this isn't always suitable. In many cases, it's a terrible idea. However, with the 'right' break, this method is not only easier but gives more secure crack closure while the glue cures. 


A comment made me realise I hadn't actually added an 'after' picture. Rectified now. Finished repair below. 

You can just make out the crack below the transition from headstock to neck (although—if I do say so, myself—you have to look pretty closely).

Turning Wood For The Mangled Headstock

If your headstock looks like this, it's probably an indication that something's gone wrong along the way.

It's not pretty

Turning some maple so it's round (and the right size for the holes). I've no idea why that nut's there. 

The previous owner of this bass had left the current owner with some very badly fitting tuners. There was a heap of wood gouged out to try fit some locating keys on a set of tuners and the shaft holes had been badly enlarged and were weird egg shapes (as well as being a poor fit for the tuner bushings).

After I'd trued up the shaft holes, they were far too big. The solution was to turn down a square-cut piece of maple in a lathe until it was a nice, snug fit for my round hole. 

That's how you fit a square peg in a round hole. 

Now to drill a correctly sized hole for the tuner shafts.

Repairing a Nasty Headstock Break

I’ve written a bit about headstock breaks before. I get to see a lot of them. Probably ninety percent tend to fall into a category I call “Gibson-Style Headstock Breaks” and are usually relatively straightforward to repair.

The other ten percent can prove a bit more challenging, though.

That's a nasty break

This one’s nasty. It’s a ‘short’ break meaning there’s not much glueing surface to provide ‘grip’. It's also got some nasty splintering and, while the owner thought to collect some of the loose splinters, most of these won’t jigsaw back cleanly (and there are some missing).

If ever a headstock repair needed reinforcement, this is it.

Splining is one option for reinforcement but there’s too much damage here to make that a viable option (and, as an aside, the truss-rod has a pretty big ‘anchor’ that leaves little room either side of it).

Nope. We’re going overlay on this one. Again, I’ve written about overlays before (here and here for example).

The wrinkle on this repair is that there’s some serious splintering and I want to be as sure as possible.

Double-overlay, baby!

Overlay on the front and the rear.

Lots of photos follow:

As usual, I have to repair the break first to get the headstock reattached. While this isn’t too much trouble, there’s no way the repair could stand up to string tension without additional reinforcement.

Partial overlay on front of broken headstock (untrimmed)

The front first. I wanted to keep the maker’s logo intact so I removed some wood for the overlay and ‘feathered’ it towards the end of the headstock. The image above shows the inlaid overlay before the edges were trimmed.

Zoomed section shows feathering from new to existing wood

You can (probably) see in the side view photo. There’s a ‘fade’ from the existing wood to the overlay I’ve added. I’ve still extended the overlay well past the break so there’s plenty of good wood for it to grip.

Overlay trimmed and re-drilled for tuners

Above is the trimmed front overlay. The raw wood is the new section and the black headstock end is (obviously) the pre-existing section. I've re-drilled the tuner holes that were covered by the overlay. It's a good idea to do that now. If I'd waited until the back overlay was on, I'd have lost them. ;-)

The backstrap overlay. 

Now around the back. Again, I remove wood from around the repaired section and into the good wood either side. Then a new piece of wood is inlaid into this ‘lower’ section to bring it back to the height of the original wood. These glued-in overlays provide a lot of strength to the repair. 

Because the headstock is angled back, I pre-bend the overlay/backstrap before it's inlaid. Some more info on the backstop bending if you want it. 

The feathered transition from old to new is clearer here

Cleaned up around the front and applied some sealer. This lets you get a better look at the feathered edge of the overlay—the transition between new and existing.

A little lacquer tidies things up

Now we’ve got some colour and lacquer applied. Everything’s nice and tidy and, as you can see, it’s strung-up and holding. Great.

And around the back, it's looking ok too. 

Around the back and the clear finish means we can’t have an invisible repair but it’s pretty discreet.

Not too shabby, I reckon.