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


Excerpt from the September/October 2021 issue of Acoustic guitar | By Martin Keith

Q: I recently bought a used guitar and took it to my technician for setup (the action was too low). He put a ruler on the frets, took a measurement and told me it would take at least $400 to get it playing properly. What is going on? The guitar looks brand new. Amy Wilson, via email

A: Funny you ask – I’ve had pretty much the same situation in my store twice in the last month. It’s a reminder of the potential pitfalls of buying a guitar without a warranty. Sometimes even expensive brand name guitars can suffer from geometry errors that make them nearly impossible to tune properly. It seems that your guitar suffers from the same unfortunate problem as my customers’ guitars: an “over-tuned” neck angle. Let’s discuss what it is, how it can happen, and why it’s such a problematic issue.

Almost all flat top acoustic guitars have their necks angled slightly. A quick look at the guitar illustrates why this is necessary – the neck is only about 1/4 inch thick where it joins the body, but the bridge is usually about 3/4 inch thick. 8 inch above the top. Additionally, many guitars have domed tops, which further elevate the bridge. To keep the string action reasonable, the neck should be set back slightly, so that the strings gradually rise above the top as they move toward the bridge.

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

Shallow neck angles like this are very common and have been accepted as a reality 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 right it can be invisible, stable, and as beneficial to a guitar’s market value as for its playability. The situation we face here is less common – 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 within a reasonable range. In the worst case I’ve seen, the bridge/nut would have had to be almost as high as an archtop bridge to play properly – about 3/4 inch!

So what to do with such instruments? Can you just put extra tall bridge saddles in there? This may work as a short term solution, but you should expect side effects contrasting with those caused by too low decks: the torque/twist on top will be significantly increased by too high decks, which can easily lead to over-distortion, loose struts, cracked deck plates, and decks that crack or peel. Most guitar bracing designs are designed for a certain amount of stress and will quickly fail if put under excessive strain. Even if the guitar manages to hold together, most luthiers agree that an overloaded top will sound muffled, compressed, and unmusical. In cases where I simply had to get such an instrument played without a large investment, I suggested that the player use extra light strings (.010 or .011 gauge) to give the guitar half a chance of surviving the additional load.

How about a neck reset – can a luthier just lower the neck angle? Unfortunately, it’s not as simple as it may seem. In a typical reset, the luthier will carefully shave the neck heel wood and usually add a thin, tapered wedge under the fingerboard extension to keep it in plane with the rest of the neck. However, correcting an oversized neck would require the opposite: adding wood to the base of the heel and planing the wood under the fingerboard extension. While technically possible, this would be much more complicated to touch up aesthetically, and the resulting tapered fingerboard 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 get the guitar playing properly, fully inform the customer of the underlying reasons for the issues, and refer them to warranty support if that’s an option. I usually also need to explain to them how to spot some of the structural problems that can occur when keeping an overloaded guitar under tension. And while I don’t generally prefer deck support systems, I might consider adding one in an extreme case where the deck too high presented an existential threat to the top.

This all serves as a reminder that neck angle should be on everyone’s checklist when evaluating a guitar to buy, whether new or used. The two crates that came through my store were outdated at the factory, and both were made by reputable companies.

If you’re buying in person, a simple peek into the fretboard can sometimes be enough, but better yet, bring a 24-inch ruler and lay it across the frets (making sure to avoid the nut). The plane of the fret tops should line up fairly closely with the top of the bridge (not the saddle, but the wooden bridge itself). If it’s much lower, the guitar probably needs a reset. If it’s much higher, it can be difficult to bring the action into a playable range without real exploits.

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When buying online I would consider it both reasonable and advisable to ask the seller for photos showing this measurement of the ruler and bridge, and many of the best online vintage guitar dealers have already begun to include such photos in their listings. This can go a long way to avoiding big disappointments down the road.

You have a question?
Not sure about the care and maintenance of your guitar? The ins and outs of guitar making? Or another topic related to your equipment? Ask Acoustic guitarMartin Keith’s repair expert by sending an email titled “Repair Expert” to [email protected] and we will forward it to Keith. Yes HER selects your question for publication, you will receive a free copy of HERit is Acoustic Guitar User Manual.


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