How to Fix Problems Caused by Incorrect Neck Angles on Acoustic Guitars

Q: I recently bought a used guitar and took it to my tech for a setup (the action was too low). He put a ruler on the frets, took one measurement, and told me that it would be at least $400 to get it to play right. What’s going on? The guitar looks brand-new. —Amy Wilson, via email

A: Funny you should ask—I’ve had nearly the same situation come through my shop twice in the last month. It’s a reminder of the potential pitfalls of buying any guitar without a warranty. Sometimes, even expensive name-brand guitars can suffer from errors of geometry that make them almost impossible to set up correctly. It sounds like your guitar is suffering from the same unfortunate issue that my clients’ guitars exhibited: an “over-set” neck angle. Let’s discuss what that is, how it can happen, and why it’s such a problematic issue.

Nearly all flattop acoustic guitars have their necks attached at a slight angle. A quick look at the guitar illustrates why this is necessary—the fretboard is only about 1/4-inch thick where it joins the body, but the bridge is usually 3/8-inch or so above the top. Additionally, many guitars have domed tops, which further elevate the bridge. To keep the string action reasonable, the neck must be pitched back a little, so the strings get gradually higher above the top as they travel towards the bridge.

Neck angle is probably the single most crucial variable for the playability of a flattop guitar. If it is too shallow, the action will never be low enough to be comfortable, unless the bridge gets shaved down to a fraction of its ideal thickness. This was a common approach in years past, as a way of avoiding the cost of a full neck reset. However, lowering the bridge causes problems of its own: It reduces the torque/twisting pressure of the strings on the top, which robs the instrument of responsiveness and volume. It also reduces the bridge’s structural contribution to the top, which makes future failures more likely.

Shallow neck angles like this are very common and have been accepted as a fact of life for vintage guitars. The process of resetting the neck angle by removing the neck and recutting the joint has become widely accepted, and when done well, it can be invisible, stable, and as beneficial to a guitar’s market value as it is to its playability. Less common is the situation we’re faced with here—an instrument where the factory neck angle is too steep. In these cases, the bridge and saddle must be comically high to get the action in a reasonable range. In the worst case I’ve seen, the bridge/saddle would have needed to be almost as tall as an archtop bridge in order to play properly—about 3/4-inch!

So what is to be done with such instruments? Can you simply put extra-tall bridge saddles on them? This can work as a short-term solution, but you should expect contrasting side effects to those caused by bridges that are too low: The torque/twist on the top will be dramatically increased by overly high bridges, and this can easily result in excessive top distortion, loose braces, cracked bridge plates, and bridges becoming cracked or unglued. Most guitar bracing patterns are designed for a certain amount of stress and will fail quickly if subjected to excessive tension. Even if the guitar manages to hold together, most luthiers agree that an overloaded top will sound choked, compressed, and unmusical. In cases where I’ve simply had to get such an instrument playing without a big investment, I’ve suggested that the player use extra light (.010 or .011 gauge) strings to give the guitar half a chance of surviving the extra load.

How about a neck reset—can a luthier just lower the neck angle? Unfortunately, this is not as simple as it may sound. In a typical reset, the luthier will carefully shave away wood from the heel of the neck, and usually add a thin, tapered shim under the fretboard extension to keep it in plane with the rest of the neck. However, correcting an overset neck would require the opposite: adding wood at the base of the heel, and planing away wood from under the fretboard extension. Though technically possible, this would be vastly more complicated to touch up cosmetically, and the resulting tapered fretboard extension would be nearly impossible to detail in a way that looked normal.

My usual approach in these cases is to do the least invasive thing possible to make the guitar play adequately, inform the client fully about the reasons underlying the issues, and refer them to warranty support if it is an option. I usually also need to run them through a quick primer on how to spot some of the structural issues that may arise from keeping an overset guitar under tension. And though I don’t usually prefer bridge support systems, I might consider adding one in an extreme case where the overly tall bridge presented an existential threat to the top.

All of this serves to remind that neck angle should be on everyone’s checklist when evaluating a guitar for purchase, whether new or used. Both of the cases that came through my shop were overset at the factory, and both were made by well-regarded companies. 

If buying in person, a simple glance down the neck can sometimes be enough, but better still is to bring a 24-inch ruler and lay it on the frets (making sure to avoid the nut). The plane of the fret tops should line up quite closely with the top of the bridge (not the saddle, but the wooden bridge itself). If it is much lower, the guitar likely needs a reset. If it’s much higher, it might be difficult to get the action into a playable range without some real heroics. 

Buying online, I’d consider it both reasonable and advisable to request photos from the seller which show this ruler-and-bridge measurement, and many of the better online dealers of vintage guitars have already begun to include such photos in their listings. This can go a long way toward avoiding some big disappointments down the road.

Got a Question?
Uncertain about guitar care and maintenance? The ins-and-outs of guitar building? Or another topic related to your gear? Ask Acoustic Guitar’s repair expert Martin Keith by sending an email titled “Repair Expert” to Editors.AG@stringletter.com and we’ll forward it to Keith. If your question is selected for publication, you’ll receive a complimentary copy of AG’s Acoustic Guitar Owner’s Manual.

This article originally appeared in the September/October 2021 issue of Acoustic Guitar magazine.