My homemade fret slotting jig is one of the most popular tools I teach how to make in my book, Acoustic Guitar Making: How to make Tools, Templates, and Jigs. This jig allows you to make copies of any fretboard that you already have. I made mine from scraps. This saved me tons over a store bought jig.
Fret Slotting Jig Design
The jig is essentially a miter box. However, there is a lot more to it. A standard miter box still requires the user to position the wood correctly before making a cut. When making a fretboard, the accuracy is very important. Positioning the saw by hand for all the frets is not the easiest way to be accurate. The way this miter box is made, it eliminates any hand work and makes the slots more precise.
The basic construction is to make a miter box, and cut it in half on a miter saw a few inches from the end. Before cutting, screw a small piece to the top. In the picture, this is the Rosewood piece. It adds a little more surface area once the box is cut in half. Just make sure it’s not taller than the depth of your fret saw blade. The two halves are then screwed to a base board with the indexing bar in place. The indexing bar determines where the saw will make a cut. Plus, the slot is only wide enough for the saw to fit, increasing the accuracy.
The first step is to eliminate the need to position the board by hand for each cut. A indexing bar is added below the saw slot that fits exactly into a fret slot. For my jig, I found an old razor blade and it happened to fit right inside a fret slot without any wiggle.
This thin piece of metal sits right at the bottom, and is screwed to one of the miter box faces to keep it secure. It should stick out just as deep as the slots on your template fretboards. This is what the template fretboard locks onto when cutting, ensuring that the new slots are cut in exactly the same place. Essentially, using the indexing feature of the jig, you can make exact copies of any slotted fretboard you have.
Creating the Saw Blade Slot in the Jig
The next step in making the jig more accurate is to make the slot for the saw only a small fraction wider than the saw blade. This was done by carefully positioning the saw and between the faces before screwing it down. You can slide a few sheets of paper or a playing card in between so you have a little movement after you screw down the miter box.
While you are setting up the two halves of the miter box, clamp them in place. Test the saw action to ensure that there is free movement. As long as the saw doesn’t bind or wiggle, the placement is good, and the halves can be screwed down to the base plate.
The best template fretboards for the fret slotting jig are flat, and not tapered. Buy the size or sizes that you commonly use from a guitar making supplier like Lmii or StewMac. Order a slotted board, and you will have a template that you can use forever to make copy after copy.
In order to use the jig, you need to create some fretboard blanks. These need to be the same size as the template fretboard, because they will be sent through the jig together when cutting the slots.
A fret slotting jig can be made from scraps in the shop, is very accurate, and makes exact copies of any template fretboard that you already have.
The length of the blank does not really matter as long as you have enough to use the fretboard on a guitar, but the width needs to be the same as the template board. Wrap the two ends with masking tape a couple times, and it will secure the pieces well enough to be passed through the jig and not come apart. The wrap at the nut end can fit between the nut and first fret with standard size masking tape.
Using the Fret Slotting Jig
Push the fretboard into the box until the first fret slot on the template fretboard seats itself on the metal indexing bar in the bottom of the jig. This will lock the boards into position, ready for the first cut.
Hold down the boards with one hand and operate the saw with the other to create the slot for the first fret. It can be difficult to know how many strokes you will need to complete the slot without going through. If you try a test cut on a piece of drop from one of your blanks, you will easily be able to count the strokes and see how many it takes to cut about half way through the board.
Once the slot is cut, advance the board forward to the next slot. The template board will seat on the indexing bar. Then, hold down the boards and cut the second slot. You will feel the board drop into position as it is moved forward and a new slot reaches the indexing bar. It will not need to be forced, and it should drop nicely into place over the bar.
This process is then repeated over and over until all of the fret slots are cut. The fret slotting jig will work just the same on every slot, and at the end you will have a very accurate copy of the template fretboard. Keep your saw level for the cut.
Once completed, take a look at the end of the board to ensure that all the slots have been cut correctly. It is hard to see inside the jig, so sometimes a slot is missed. If that happens, put the pieces back inside and cut the missed slot.
When you are satisfied with the board made with the fret slotting jig, remove the tape and your fretboard slotting is complete.
A fret slotting jig gives you more custom options in the shop. Pre-slotted boards are nice to work with, but they are limited in species. When you are able to slot the boards yourself, your wood choice is far more open.
I have a video about my Fretboard Slotting Jig that shows more angles, as well as how to make it. I provide all the dimensions in my book, but anyone who reads this article and watches the video should be able to put one together in their shop easily. I would be honored if you bought my book, but to make this jig you shouldn’t need to.
My Fret Bending Jig article tackles another shop jig that is very easy to make, and you can Make a Custom Pick Guard with this video. The pick guard video shows a great way to add another custom element to your guitar.
If you are new at guitar making, and working on getting your tools and jigs made, do not be discouraged. Anyone with some patience and time can make a nice guitar, even on the first try. I tell the story of My First Guitar as a precautionary tale. Take your time on your builds, and your first will look far better than mine. Remember, it’s more about where you end up than where you start.
Lastly, if you are going to make a guitar, you will need a good book. No matter what anyone says, you can make a great instrument from a book. Here are my Top 5 Acoustic Guitar Making Books to get you started. If you pick up a couple of these, and spend a little time in the shop, you can make a guitar that you will be proud of.
What’s your favorite homemade guitar making jig? Let us know and we can all make better instruments. Happy building.