Everything you wanted to know about how to shim a guitar neck

How much shim do you need to add?

Luthiers have measurement tools and years of experience to determine how much angle a neck needs to be raised to achieve proper string height.

Non-luthiers (which is everyone else, and that most likely includes you) just guess and hope for the best.

If you have absolutely no idea how thick your shim should be, start thinner and then move up to thicker if need be. You don't need much and shouldn't have to go any thicker than a credit card's thickness.

Yes, this may mean you have to take off and on the neck a few times before you get the neck angle you're looking for. You can be comforted by the fact that almost nobody gets it right on the first try. This means you can safely expect to have to take the neck off at least twice or possibly three times to get that shim height just right.

How to deal with factory shims?

This is the last thing I'll mention, and it's important to talk about.

If you've determined that yes, you need a shim, but you've never taken the neck off your guitar before, you may be in for a surprise or two and need to prepare for it.

For any guitar that sold new for under $1,000 USD, take that neck off slowly the first time you do it, because you may find weirdness.

The weirdness I'm referring to is paint chips and possibly a makeshift shim in there "installed" by the factory who made the guitar.

Before I get into that, most guitars with bolt-on necks that sell for over $1,000 USD will have a properly made neck pocket where you won't find any paint chips. And if you do find a shim in there, it will have been made properly.

For the sub-$1,000 stuff however, what may happen when you take off that neck is see a few pieces of very thin wood (similar to balsa wood) fall out of the pocket.

Those pieces you find, if any, were put there by the factory. On the production line, the guy who put together the guitar noticed that the saddles were too low. He then quickly took off the neck, grabbed a few slivers of scrap wood, threw them in the neck pocket, put the neck back on, set up the guitar again, cleaned it up and then sent it on down the line to be shipped.

This happens a lot on sub-$1,000 guitars. And if it's on yours, that's totally normal.

Does this mean the shim put in there by the factory failed? No. The shim was put in there to get the guitar "good enough" for sale. When you bought the guitar later and went to lower the action, the existing shim simply wasn't thick enough.

In the end, if you find what seems like random pieces of wood in the pocket on first neck removal, don't be surprised by this. It's not random. It was just a guy on the production line that put in the absolute least amount of effort to get the guitar ready for sale.

Don't reuse those garbage pieces if you find any, by the way. Create a proper wedge shim either by buying one or making it yourself. Anything is better than what was in that pocket originally.

Published 2020 Feb 27