neck-angle

Neck Shimming Made Easy

I’ve written about neck shimming a while back, but the world of shimming has moved on and it’s worth an update.

Why would I have to shim a neck?

Two reasons:

  1. Even when you’ve lowered your bridge saddles as far as you can, your action is still too high.
  2. You want to purposely raise your bridge to get a steeper string angle over it. This can be helpful on Jazzmasters and Jaguars (where the strings generally go over the bridge at a quite shallow angle which reduces downward pressure and can cause hassle).

How would I go about shimming a neck?

Well, here’s how you would not go about it:

  1. By using Fender’s Micro-Tilt adjustment thing.
  2. By installing a popsicle stick, or similarly sized shim at the end of the neck pocket.

It’s my opinion that shimming in this way can contribute to and/or speed a hump/ramp/ski-slope condition at the end of your fretboard. This can mean fretwork to resolve so you’d prefer to avoid it if possible.

Check out my How To Shim A Bolt-On Neck article for a more in-depth explanation.

What’s the correct way to shim a neck?

You need to avoid any ‘air gaps’ between the neck and body. This means a ‘full-pocket’ shim.

That's a wedge-shaped piece of wood that will angle the neck backwards but will allow good solid contact between neck and body, with no gaps.

Now, if you’ve read that previous article, you’ll have learned what a pain in the butt it is to actually make these shims. It’s a fiddly job that used to be only for the bravest of shimmers.

Until recently.

Stewart McDonald have figured out a way to reliably manufacture full-pocket, wedge-shaped shims*.

Check it out.

You can buy a shims with different angles — a 0.25°, 0.5°, and a 1° wedge. The 0.5° should be enough for most jobs but it’s nice to have the option of something bigger (the bigger one is useful for the offset Fenders when you're deliberately trying to raise the bridge height).

The shims fit a standard neck pocket and even have a marked line to show where to cut for a squared-bottom pocket.

I’ve used them for the first time today and I’m a happy repair-guy. I’ve hated making these shims in the past and being able to buy them is one less source of stress.

When I originally wrote this article, only guitar neck shims were available. Now, Stew Mac has tapered bass shims too (and some 'blank' shims in case you've a weird sized pocket). 

Don't just use a short shim at the bottom of the neck pocket. Shim your neck with a full-pocket shim to prevent ramps/ski-slopes.

It's a bit difficult to see the 'wedge' shape of this shim bit it's thicker at one end and feathers to almost nothing at the other. This is perfect to properly shim a guitar neck. 

*It has been possible to buy ‘flat’ shims—a consistent thickness all along. You could use these to shim a neck but, because you’re not angling the neck, you need to add a much thicker flat shim to achieve the same result. It’s not the best solution. 

Martin Neck Reset - Easy

About a month ago, I had a spate of neck resets that fought and fought. They just didn't want to cooperate. I'll write something about one of these in a little while but, for the sake of my sanity, I'd like to remind myself that, sometimes, they go well.

If you want a recap on why we reset necks and what's involved, check out my neck reset primer

Getting the neck off

If you’ve a bolt-on neck, life is considerably less messy. If you’ve a dovetail, glued-in neck, well, then we need to break out the steamer. But first, the fingerboard extension.

I apply heat to the fingerboard (carefully, obviously). In this case I’m using a heating blanket. I used to use a shaped metal block that was heated separately and then popped in place but the blanket makes things much more easy. Some poking around with spatulas helps loosen the glue. Often, it'll take a few heating/poking sessions to get things freed up.

Heating fingerboard extension to loosen glue

Loosening fingerboard extension for neck reset

Then the fun begins. Steam.

I remove a fret and drill a little hole, through the slot, into the dovetail cavity. There’s usually a small gap at the back. Once I have access in here, I fire up the steamer and begin to inject steam, through a nozzle, into the cavity. As I do, the hot steam will gradually soften the dovetail glue.

How much steam and how often it's applied varies from guitar to guitar but it's best to use as little as possible. There's quite a bit of wiggling and wrestling with a guitar as I try to get the glue to give up its grip. That wooden contraption around the guitar helps a lot. It provides some 'upward' pressure to help encourage the neck to move out of the dovetail as I wrestle with it. You get a feel for it—when to go with more steam, when to wiggle and, after a while…

It pops out. Brilliant.

Steam to remove guitar neck during reset

Dovetail neck joint disassembled

Setting the neck

Exaggerated illustration of neck reset

The neck angle is altered by taking a 'wedge' of wood off the heel. The image shows an exaggerated view of this—the green section is removed so that when the neck is reattached, it tilts back. 

It's really important not to take wood off the pointy bit of that wedge as doing so would move the neck closer to the bridge and actually alter the scale-length, throwing your intonation all out of whack. 

 

Chisels and sanding 'sticks' get most of the wood off.  When I've taken off enough to get me close to where I want to be, I finish off by moving to strips of sandpaper. Using then as shown lets me take off the last, smaller, amount of wood but also lets me get a good fit between neck and body. Taking more off one side or the other, during this stage, also allows me to adjust the side-to-side fit so the neck sits properly on the centre-line.

As I proceed, I'm constantly checking the set-angle (by sighting along the board), the centre-line set (by using a long straight-edge along the neck), and the fit between neck-heel and guitar-sides. 

 

Fitting neck-heel during reset

Checking neck set-angle

Checking neck alignment during reset

Putting it all back together

When everything's right, it's time to reassemble. Generally, the dovetail joint needs to be shimmed as our angle-changes will have altered the way the joint sits together. A couple of test-fits get me where I want to be and then it's time to heat up the glue-pot. In usual Martin-style, the glue goes only on the dovetail joint and under the fingerboard. The heel and body do not get glued on a Martin. This is one of the reasons Martin resets tend to be a little easier.

A properly fitting dovetail pulls itself together. A clamp for the joint and one for the fingerboard is all I need.

Reassembling acoustic guitar after neck reset

Dovetail neck joint re-glued

I like to leave things overnight for the glue to cure—probably overkill but it makes me feel safer. Clamps off and I make a little rosewood plug to fill the hole I drilled earlier. Once that's glued in, I can re-cut the fret-slot through the plug and reinstall the original fret. 

Plugging the 'steam hole'

Plug with slot cut. Will be hidden under the reinstalled fret

Some neck-sets require a full refret afterwards but we're good on this one. Only minimal fret-work is is needed. Also, Martins don't usually need any finish touch-up so this guitar's playing again—with a new saddle and a comfortable action—in no time at all. 

Textbook. Nice.