Introduction: Bass Ukelele From Old Acoustic Guitar Neck

About: Sucker for electronic hobby projects

It all started with an old acoustic guitar I had for many years. However it could not be tuned anymore and last years the thing started to tear apart. When the backside came loose I was a the point of throwing it away. The neck however was still okay and so the idea came up to use it in my first instrument project.


- old guitar neck

- wood for new fret board

- wood for the body

- Pax fret saw

- Fret wire type Dunlop 6230

- Franklin Titebond glue

- Instant glue

- Dot white pearl 6 mm for the position markers on the front of the fretboard

- Dot stick 2 mm for the position markers on the side of the fretboard

- piezo pick up with electronics to power the thing

- M4 stainless steel studs

- M4 stainless steel nuts

- M4 stainless steel round nut

- a lot of sanding paper with different grains

Step 1: Change the Fretboard to Make It a 21" Scale Length Guitar

The acoustic guitar probably had a scale length of around 26". I wanted to make a bass like the ones that Kala sells, which are based on 21" scale. So the old fretboard had to be taken off. There are quite some interesting sites to be found on the internet showing the removal of fretboards. They all involved some way of heating so I used an old standard clothing iron to heat up the fret board and carefully sticking a putty knife between the board and the neck, trying to keep the neck intact.

Step 2: Cutting the Body

I got a nice piece of oak wood from a friend that was a left over. I guess any solid wood piece you can get would be suitable. Mine is only 37 mm thick so I think that is close to the minimum you can use. In an old Cad program I copied the shape of a Kala U bass and plotted it scale 1 on paper so I could take it over on the wooden plate. With a standard electric jigsaw I cut the shape out of the plate. Make sure your saw is sharp enough.

Step 3: Installing a New Fret Board First Time But Wrong :-(

I also would like to inform you about the mistakes I made in this first project so hopefully you can learn from it and don't make the same as I did. From a guitar parts shop I bought a piece of Rosewood which is commonly used for fret boards. I made a mistake here to glue the fret board on the neck without first making the cuts for the frets. Once the fretboard was glued on the neck I tried to saw the fret grooves in the neck. However due to the round neck I could not get it properly secured and the sawing of the frets became a mess. As you can see on the last photo it looked okay but after having screwed up the fret grooves I had to take of the fret board and throw it away.

Step 4: Installing New Fretboard Second Try

So after getting a new piece of Rosewood I first made sure the fret grooves were sawed in. You can use an easy tool from the Stewmac website to determine the right fret distances. In my case for 21" I calculated the distances with an excel sheet I wrote with the formula all these calculators are based on, see photo of the formula.

In order to make the fret distances as accurate as possible I used my old Cad program to draw a template and plot it out scale 1. I used the plot to take the distance over on the wood.

To make sure that the sawing of of the frets was accurate and parrallel I made first a mitre with some small bearings that normally are used for skate boards. The saw I used is a special one that I bought on the internet for guitar Luthiers, brand Pax. It is exactly the width of the fret wire (0,5 mm).

After the fret slots were sawn I took the old fretboard to cut the sides off roughly in the same shape making sure some extra wood was still present so once the fretboard is glued on you can sand the sides to match it with the neck.

Last step is glueing the fretboard on the neck. From different internet sites I understood that the Titebond glue is most used for this and so I bought a flacon of it at the guitar parts shop and used it to glue the fretboard.

Once the fretboard was glued I drilled the several holes for the position markers at the front and the side. After glueing the markers in I grinded the complete fretboard with fine grain sanding paper.

Step 5: Installing the Frets and Tuners

For the frets I used the Dunlop 6230 type wire which seems to be common used for bass ukeleles. You just hammer them in and cut the surplus at the sides. After all frets are hammered in you will need to file of the sharp edges by using a file and sanding stone.

For the tuners I had purchased some old used bass tuners on e-bay for a decent low price. Obviously you can also buy new ones but I wanted to keep it a low cost project. In order to be able to accept the thick polyurethane strings (Aquilar Thundergut) I had to drill up the holes a bit. So the E string tuner had the biggest hole (5 mm), the A tuner 4,2 mm, the D tuner 3 mm and the G tuner did not need to be drilled as it was wide enough for the 2,4 thick string.

As the tuner diameters were substantially bigger than the holes in the neck I also had to enlarge these diameters. As a guitar has 6 strings and a bass only 4 I left the 2 middle holes open. I have filled them up later and placed a string holder over it to cover the filled up holes.

Step 6: Shaping the Body

After sawing the body the edges are quite sharp. To smoothen the sides I used an electric woodrat machine (I hope this is the right english translation). Furthermore a lot of sanding by hand in order to make the complete surface smooth at all sides.

Also the pocket for the neck and the string knots at the back side were cut with the woodrat machine. When the neck was tightly fit in its pocket I determined the string length and bridge position (the distance from the nut to the bridge should be exactly the scale lenght of 21"). After drilling the holes for the string and a lot of final sanding I varnished the body with a first layer of polyurethane. Also the backside and side of the fretboard were varnished with the same material. The fretboard itsself should not be varnished.

Step 7: Making the Bridge for the Piezo Element

The piezo element is some standard one I purchased on Ali Express. The bridge had to be adjustable in height so I used some M4

sorry, will finish the instructable later. Takes more time than I thought! Be patient, rest will follow.