Electric Guitar Neck Shims

Electric Guitar Bolt-On Neck Resets

Ernie Ball stock shims
The Neck Pocket Of A Bolt-on Neck Electric Guitar Showing Shims

Shimming a Bolt-on Neck Guitar

When performing a setup on a bolt-on necked electric guitar, shims are a way to quickly adjust the angle at which the neck joins the body, facilitating the desired action adjustment.

An assortment of improvised shims that were found in this guitars neck pocket

In our shop, we commonly find improvised shims installed in the neck pocket. They range from purpose-built plastic shims like those pictured at the top of the page, to a hodgepodge of items like sandpaper, cardboard, and/or guitar picks.

 The idea behind this practice is that placing a piece of material near one edge of an otherwise flat neck pocket causes the neck to sit at an angle once it is screwed down on top of it; The side with the shim installed will be higher than the side without. Technically speaking, this is a basic neck reset.

While these crude shims are an effective tool for changing the neck angle, they do so with the risk of unintended consequences: Using improvised shimming techniques prevents the bottom of the neck from evenly contacting the entirety of the neck pocket. There will inevitably be a gap between the shimmed and non-shimmed ends. This gap adds torsion to the neck in-between the neck bolts while also allowing humidity to more easily penetrate the area. Over time, necks shimmed in this haphazard way are more likely to experience issues in their upper register that will require fretwork or refret to correct.

The Fender Micro-Tilt

Anatomy of a Fender A Micro-Tilt

The Fender Micro-Tilt was introduced in 1971. It has been widely used over the years, including select models in Fender’s current lineup. 

The Micro-Tilt is a built in device for changing the neck angle. The neck angle can be increased via an Allen key adjusted set screw, attached to the body, that presses against a metal plate installed on the underside of the neck.

While the Micro-Tilt works as advertised, making short work of a neck-angle adjustment, unfortunately, they suffer from the same pitfall as the improvised shims that are ubiquitous on non Micro-Tilt equipped instruments: The neck heel loses contact with the bottom of the pocket.

Full Pocket Length Neck Shims

When adjusting the neck angle of bolt-on neck guitars, we prefer to make make full length, angled, shims. This style of shim eliminates the gap that exists when using the previously derived methods. Though requiring a bit more effort up front, they facilitate a more stable attachment and minimize the potential risk of costly repairs down the road. This style of shim is reminiscent of the design used in the NT neck joint of Taylor acoustic guitars.

Here we are using a pre-tapered maple shim that is purpose built for this job. The shim gets progressively thicker across its length by a consistent amount; In this case, 1/2 degrees.

Using these pre-started shims makes a quicker job, as the thickness sanding has already been done for us.

To fit it, we first cut the blank to match the dimensions of the neck pocket. Since it covers the entire surface area of the neck pocket, it can provide a sturdy, but tapered, base upon which to install the neck.

Next we locate the position of the screw holes and create openings in the shim so that the neck mounting screws will pass through unobstructed while tightening the neck down into the pocket.

Finally, we added a little bit of aged lacquer to the edges of the shim to protect it from moisture and help it to blend in with the baked maple neck of this guitar.

Notice that the shim is thicker towards the bottom of the photo than it is at the top. This taper is what changes the neck-angle.

Reverse Tapered Shims

The most common reason to shim a neck is to increase the neck angle, facilitating lower action. However, sometimes instruments require a shallower angle.

Fender Stratocaster with Flushed Bridge

Sometimes, even with the saddles set to their highest setting, the action in the upper register is still too low. This is a perfect candidate for a reverse tapered shim in the neck pocket.

Shimming for a shallower angle is common on Fender Stratocasters when the player prefers to have the tremolo bridge set flush to the body, or when an instrument has been assembled from miscellaneous parts that were not perfectly compatible.

Tapered Shim Before Shaping

The process for installation is similar to , the above outlines, except this time we are using a different sized shim and installing it with the thicker side towards the outside edge of the pocket instead of towards the pickup.

The Installed Shim

When finished, the larger taper does make the shim a bit more visible at the heel than when going the other way. Fortunately, by painting the edges, it can be made to blend in reasonably well.  

Making Tapered Shims

Some instruments, like this Fender Mustang Bass, have a neck pocket shape that is incompatible with the available pre-tapered shims. In these circumstances, we use our thickness sander to make our own out of a piece of maple.

Though making the shim from scratch requires extra tools and a bit of added work, the benefits are worth it. 

Using tapered shims in this way, is effective, secure, fast, and easily reversible if and when the need should arrive. They are often an integral piece to getting a bolt on neck guitar dialed in just right.

About Guitar Repair Long Island

Guitar Repair Long Island is the area’s premier destination for fretted musical instrument care and maintenance. Led by owner/head technician Erik Salomon, the shop is dedicated to providing quick, honest, and reliable service. Our vast experience in all aspects of instrument repair ensures that we can help with whatever your needs are. Contact us with any questions or book your appointment today.

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