This is How to Make an Acoustic Guitar Part Twenty Two, making the truss rod slot. In this part of the build, I’ll show you a couple ways to make the slot in the neck, with helpful tips and tricks as well. Enjoy.
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Making the Truss Rod Slot
One of the first things to do to your acoustic guitar neck before you cut out the shape or ruin the squareness of the blank is to make the truss rod channel. This is also called a truss rod slot, and it’s where the truss rod lives in the guitar neck.
This is a fairly straightforward process, which you can use a number of different power tools as well as hand tools to complete.
Obviously power tools are going to offer a faster solution, however the hand method works well too.
The goal of this portion of the how to make an acoustic guitar series is to show you how to create a well fitted truss rod slot, as well as several different ways so you can proceed confidently with one that you like. Let’s get started.
If you missed last week, Here is How to Make an Acoustic Guitar Part Twenty One
Truss Rod Placement and Marking
The first thing you need to do is pick out a truss rod that you like, and order it. In order to do the marking portion of the process most efficiently, it’s best to have the actual truss rod you’re going to use in your possession.
Read the directions that come with the truss rod, and if there’s nothing look to your guitar making book or plans for placement details. In general, the adjustment end terminates very close to the heel of the guitar neck.
Most of the time this places the other end somewhere around the third fret, but it could be a little bit closer to the nut or a little bit farther away. The adjustment end is the one you’ll end up paying attention to more.
Mark out the placement of the truss rod slot to be absolutely centered in the neck. All you need to do is find the center near the nut area near the heel area. Connect those two, and use that as your guideline for milling the slot.
Saw and Chisel Your Truss Rod Slot
The oldest method for making a truss rod slot is to use hand tools. The two major hand tools are a saw and a chisel. You can do the entire thing with a chisel if you like, but the saw helps with alignment.
Once you have your sides of the channel marked out, use a saw to make the initial cut near the heel, and tip the saw forward as far as you can to cut as much of the sides as you can. This is going to be a very shallow angle to cut.
Make one on both sides of the truss rod slot, and they will serve as a guide for removing the rest with a chisel. You can use a router chisel if you like, though a narrow chisel will also do the job.
This process can be a little time-consuming, because you’re working by hand. Clamp the neck securely, and use both hands to work the chisel to remove material from the slot. Check your depth according to the installation instructions, and stop when you get there.
Using a Router With a Guide
Another method for cutting the truss rod slot is to use a handheld router with a guide. This method brings power into the process, and the majority of woodworkers will have at least a small router hanging around the shop.
The accessory that you need for the router to make this work is a guide. This is a attachment that goes on the router that keeps it from moving left to right as you cut a slot. It’s really helpful, because it’s very difficult to push a router straight through a piece of wood.
Set up your guide so that way the flute bit on the router cuts one side of the slot. Then, run the router from end to end, and set up for the other slot. If your slot is absolutely centered, you should just be able to flip the router around and use the guide on the other side of the neck.
Make several passes when using this method. It’s difficult to dig out the entire slot at full depth with one pass of the router. This is asking for trouble, because the router is pulling quite a bit to try to make this cut.
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Instead, make several passes and increase the depth each time. Each pass will be very easy, and you’ll get to the end more safely.
See Also: Router Inlay Kit For Easy Inlays
Slotting the Rod on a Router Table
If you have access to a router table, this is also a great way to create your trust rod slot opening. The router table has a nice advantage over a hand router, and that is you can use both hands to hold your piece securely.
If you already have your headstock shape created, you’ll need to use a short piece of wood as your fence on the router table, because the headstock will hit as you push it through. However, that’s very easy to do and you only have to set it up once for each side of the slot.
Make passes on the router table very similar to the handheld router. Don’t go full depth right away, and instead sneak up on the depth with several passes through the machine. Do one side of the slot completely, and then switch to the other.
Using a Dremel Tool and Router Base
On this guitar neck, for some reason that I have absolutely no memory of, I decided to make the truss rod slot with a Dremel tool. You can use a Dremel tool and router base with a guide to create your trust rod slot very easily.
The steps are very similar to using a handheld router. After all, a Dremel with a router base is just a tiny router. For the bit, I used a spiral carbide cutting bit, which removes material very easily.
Since my bit was only an eighth of an inch in diameter, I had to make several passes for both sides of the slide, as well as a few down the middle to remove all of the material. It all comes out just the same though, and it makes for a nice truss rod slot opening.
Truss Rod Types
If you are new to making acoustic guitars, you might be surprised to find out that there are several different types of truss rod that you can purchase. They all do about the same thing, though some are a little fancier than others.
The most basic of truss rods pushes in one direction. The reason to use it on the guitar is to push the neck back and fight the string tension when the guitar is tuned to pitch. Since the strings pull the neck forward, the only job of the rod is to push it backwards.
Among this category of rod, there are several different models. Some are bigger, some have a rod inside of a housing, and some are very skinny. They all do basically the same thing though, so pick a rod with a good track record or a rod from your instructions.
Another type of rod is a two way adjustable rod. This type of truss rod allows you to push the neck both forwards and backwards depending on which way you turn the adjustment screw. This is another option for you, and lots of guitars use them.
Tips and Tricks for Making the Slot
When you’re making your trust rod slot, there are some things to know so that way you don’t make mistakes that can cost you your neck blank. Here are several:
- Make the slot as straight as possible, and take your time to get it right.
- Make several passes with your tools instead of trying to go full depth in one shot.
- Watch the rotation of your cutting bits and pass the neck through so the bit presses the neck against the fence.
- You cannot control a router without a guide, and your slot will look poor if you try.
- Use the actual truss rod itself as your measurement guide.
- When installed, the rod should not twist back-and-forth in the slot at all.
- Simple truss rods are more reliable than elaborate truss rods.
- Use the method you’re most comfortable with for making your slot.
Coming Up Next Week
In the next part of the how to make an acoustic guitar series, I’ll show you how to cover the truss rod and lock it into position in the neck. This will be a quicker part of the process, but it’s also an important part.
The truss rod itself has to be locked into place, but it also needs to be able to move freely in order to operate. This isn’t as difficult as it sounds, and I’ll show you everything you need in order to be successful.
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