It is only a matter of time for most acoustic guitars. They will eventually need a neck reset. A neck reset corrects the angle of the neck and get the string height within the correct range so that it can be fined tune with adjustments to the saddle. When the action at the bridge is too high on an acoustic guitar, you first lower the saddle by removing it from the bridge and taking material off the bottom. This is a great way to fine tune the string height, but the saddle can only go so low. The second stage (not normally recommended), might be to shave the top of the bridge. This may be an appropriate method for certain guitars that are not valuable enough to justify a neck rest. For higher grade instruments, the neck reset is generally the way to go.
So how do you know if you need a neck rest?
If the nut height is correct, the relief is correct and your saddle is already as low as it can go, you probably need a neck reset.
It can be a bit tricky to verify this, but how a luthier will check, is by using a straight edge, preferable one with notches cut out for the frets. With this laying across the fingerboard and protruding to the bridge, you should have the edge of the straight edge just touching the top of the bridge.
My neck has an adjustable truss rod, can’t this be used to adjust the action? In short, no. An adjustable truss rod is specifically designed to adjust the relief (bow) in your neck. A properly adjusted neck will be some where between perfectly straight, and slightly up-bowed. Most players prefer a setup with a slight bow in the neck, as this allows for lower string height without buzzing. Never use the truss rod adjustment to change your string height.
So if your straight edge hits low on the bridge, this is a sign that your neck is underset and will need to be adjusted. It is much less common for a neck to be overset and see the straight edge protrude well above the bridge.
Let’s be clear about this. While most acoustic guitars will eventually need a neck reset, it is no small matter having this repair done. It is one of the more difficult repairs out there. The guitar’s fingerboard is glued to the top and must be removed with heat and what is basically a spatula. There is a lot of opportunity for an inexperienced repairman to do serious damage here. We don’t want to heat the finish, or do unnecessary damage when getting the fingerboard loose from the top.
Once we have worked the fingerboard loose, we now have to deal with the neck joint. Most candidates for a neck reset will have a dovetail joint. This would be simple enough, if it were not for the fact that the dovetail has been glued together. The only way to get this apart is with steam. TO get steam in, we need a hole. This is accomplished by pulling a fret and drill a hole in the fret slot that goes into the neck joint. From here we can use a special needle to direct steam into the joint to loosen the glue. DOn’t forget to be careful removing the fret. We want to dave it, and minimize any damage to the fingerboard.
Injecting the steam into the neck joint is relatively straight forward (assuming the hole is in the correct position). The problem we have is that along with steam, comes water. We want to keep this under control and stuff rages inside the guitar to absorb the moisture. Steam will also begin to come out around the neck joint, and onto the top. This must be kept under control or it may damage the guitar.
Now that the glue is softening and the the fingerboard is loose, it is time to pull the neck off. Some may wiggle it around with some force and work it off.This does work, but can damage the guitar. The best method is to use a jig that will press the neck out of the dovetail joint. We may need a couple of more applications of steam before the neck comes loose. It is very important that we do not over-steam the joint.
If all goes well, the neck will be separated from the body with no damage to the guitar. Now it is time to start cleaning the old glue off. This is no small task. Once the glue is off, the guitar is left to dry.
TO be continued…..