How To Shim A Bolt-On Neck 

Shimming a guitar neck is an important and often overlooked part of the instrument setup process. It ensures that the neck is properly aligned to the guitar’s body so that it plays its best.

This article will explain how to shim a bolt-on neck, including what tool you need, how to understand neck angle and a step-by-step guide on how to do it correctly.

You’ll soon be able to keep your beloved instrument playing as good as new!

What is shimming a guitar neck?

Shimming is a process in which you can quickly adjust the angle of your guitar’s neck by inserting a small, tapered wedge between the heel and pocket.

It involves using a wedge-shaped piece of material to fill any air gap that may arise from ill-fitting or mismatched parts. When done correctly, this will help ensure that the bridge saddle is set at the correct height and create a better contact between the neck and body for improved sustain.

Furthermore, fretboard warping becomes much less likely with no air gaps in place. Meaning you won’t have to worry about having to redo any work after a fret dress.

How shimming affects your guitar neck angle

Shimming affects your guitar neck angle by correcting an undesirable neck angle. If the neck is set too far back or the angle is too shallow, it can result in high action (strings too far from the fretboard) or poor intonation. By installing a shim in the neck pocket, the neck can be tilted forward, effectively increasing the neck angle. This adjustment helps to lower the action and improve overall playability. Read more on how to change pickup height.

The angle of a bolt-on neck should typically be between zero and five degrees. But when an instrument ages, its body can become slightly concave, changing the neck angle and making it difficult to adjust the action or intonation correctly.

If you find that your guitar is hard to play or fretting out even when saddles are adjusted as much as they can go, then you may have an issue with a low neck angle that requires a shim.

A full-pocket shim should fit inside the entire neck pocket and be shaped like a thin wedge with the taller end facing towards the bridge – this will raise up one end of the fretboard slightly in order to correct an excessively low neck angle.

What tool do you need to shim a bolt-on neck

To shim a neck, you will need:

  • Full-Pocket Shim: A shim specifically designed for guitar neck pocket adjustments.
  • Paper Hole Punch: Used to create the shape of the shim from a suitable material, such as thin cardboard or veneer.
  • PH2 Screwdriver: To remove and reattach screws that hold the neck to the body of the guitar.
  • Scissors: Necessary for cutting the shim material into the desired shape and size.
  • Sharp Pencil: Used for marking and tracing the outline of the shim on the material.
  • Marker Pen (matching body paint job): To mark reference points on the shim or guitar body for future adjustments.
  • Calipers (optional): A measuring tool that can be helpful for precise measurements, although not essential for shimming.

Make sure to prepare some additional setup tools:

  • Fresh Strings: It’s recommended to have a new set of strings for the setup process.
  • Tuner: Used to accurately tune the strings after the shim has been installed.
  • String Winder: Makes it easier to remove and replace the strings during the setup.
  • String Cutters: For trimming the excess string length once the setup is complete.
  • Truss Rod Allen Key: In case any adjustments to the truss rod are necessary during the setup process.

Having these tools on hand will ensure that you have everything needed to successfully shim your guitar’s neck and achieve the desired angle adjustment. Remember, if you’re unsure about performing this adjustment yourself, it’s advisable to seek assistance from a professional guitar technician or luthier.

How to shim a guitar neck – Step-by-step

purpose-built plastic shims

Here’s a step-by-step guide on how to shim a guitar neck:

Truss Rod Adjustment:

  • Tune up the strings with a capo on the 1st fret and fretting at the 15th fret.
  • Use a feeler gauge to measure the clearance between the bottom of the string and the top of the 7th fret. It should be around .007′ (0.18mm).
  • If the truss rod setting is good and the clearance is within the acceptable range, proceed to the next step. If not, consider adjusting the truss rod.

Nut Clearance Check:

  • Place a capo on the 3rd fret of the guitar.
  • Test the clearance between the bottom of each string and the top of the 1st fret using a feeler gauge. Each string should have a clearance of .004′ (0.10mm).
  • If the nut clearance is not within the desired range, it may require filing or replacement. Seek professional assistance if needed.

Saddle Height and Action Check:

  • Check the action at the 12th fret. As an average, the distance between the bottom of the string and the top of the 12th fret should be around 2mm for the sixth string and 1.5mm for the first string.
  • If you cannot achieve the desired action height, it indicates a potential need to shim the neck pocket.

Prepare the Shim:

  • Remove the neck from the guitar body. Before doing so, make sure to de-tune the strings to relieve tension.
  • Cut out a piece of maple hardwood veneer with scissors. Ensure that it is an appropriate size to fit into the neck pocket.
  • Using sandpaper, sand down one side of the veneer to create an angled wedge shape. This will help establish the desired neck angle.

Install the Shim:

  • Fit the shim into the neck pocket, aligning it properly to achieve the desired angle. The angled side of the shim should be facing towards the headstock.
  • Screw the neck back onto the guitar body, making sure to align the screw holes properly.
  • Tighten the neck screws firmly but be careful not to overtighten.

Reassemble and Test:

  • Tune up the strings to pitch.
  • Check the overall playability, action, and intonation of the guitar.
  • Make any necessary adjustments to the saddle height or truss rod if needed.

By following these steps, you can shim your guitar’s neck and achieve the desired angle for optimal playability. However, if you’re unsure or uncomfortable performing these adjustments yourself, it’s recommended to seek the assistance of a professional guitar technician or luthier for a precise and safe setup.


Learning how to shim a bolt-on guitar neck can make a big difference in how your guitar plays and sounds.

With the right tools and attention to detail, you can create a custom shim that improves your guitar’s action, intonation, and resonance.

If you’re unsure, it’s always a good idea to seek help from a professional guitar technician. Take your time, experiment, and enjoy the benefits of a well-adjusted neck angle for a truly enjoyable playing experience.

Here you can find more information on the different types of guitar necks.

Also, you can check out this video for more clarity: 


What is the best way to measure the neck angle?

To measure a guitar’s neck angle, you’ll need to use a straight edge and feeler gauge. Start by laying your straight edge along the fretboard, spanning from one end to the other. Then use your feeler gauge between the top of your straight edge and the bottom of your guitar’s body, near the nut on the headstock.

If you find any gaps in this area, you can determine how much shimming needs to be done for it to fit properly.

How difficult is it to shim a bolt-on neck?

Shimming a bolt-on neck is relatively easy. Just follow our step-by-step guide, and you’ll be ready in no time.

What type of wood is best to use when shimming a guitar neck?

When shimming a guitar neck, hardwoods are ideal for this task as they’re strong and durable. You can also use maple, mahogany, or rosewood. However, softer woods such as poplar can also be suitable, depending on the desired outcome.

You should also take into consideration the grain orientation. It’s best to opt for straight-grained wood with consistent coloration. Finally, make sure to select pieces that have been properly cured and kiln-dried so you don’t run into any issues down the road.

How often should a guitar neck be shimmed?

How often should a guitar neck be shimmed depending on the type of wood used, the climate, and the instrument’s age.

To ensure your guitar’s playability and tone remain consistent, it’s best to check the neck for any changes every few months or so.

If you notice that your guitar has gone out of tune more frequently than usual or there’s an extra buzz in certain frets, then your guitar’s neck may need a shim. On the other hand, if some of your frets don`t resonate as they should, probably you have dead frets and you need to change them.

With just a little bit of effort, you can keep your instrument playing like new for years to come.

Are there any risks associated with shimming a guitar neck?

Shimming your guitar neck carries some risk. If done improperly, the angle of the neck can be changed too much and cause it to bow or warp, which could make playing difficult. In some cases warped neck can be fixed, depending on how much it is warped exactly.

Additionally, shimming too much can affect intonation and sound quality. If you’re not confident in your ability to properly measure and complete the job, we advise you to seek help from a proffesional.

Leave a Comment