Introduction: 5 String Bass Guitar Out of an Acoustic Guitar

I was looking for my next project and while cruising through Craigslist and Kijiji I came across an inexpensive 3/4 size acoustic guitar. I thought that for the price, I would try turning it into an acoustic bass guitar and I have always wanted to learn to play the bass. It will add to my ukulele and guitar collection.

I decided to make my own version of a five string bass for aesthetic reasons and just to be different. I used the four bass strings and the top E string from the acoustic set.

I bought:

  • acoustic guitar (used the original tuners)
  • New nut
  • D'Addaario Short Scale, Regular Light Gauge bass strings


  • Small file set
  • Cordless drill and 7/64 bit
  • Diagonal Cutting Pliers
  • Socket set - remove tuners

Take apart Donor Guitar

  1. Loosen the strings and pull them out (keep them, I reused the top string)
  2. Remove three tuners on the left side of the head.
  3. Remove nut (keep it as well for trial setup)
  4. Give the guitar a good polishing while the strings are off and you can access all of the body.

Step 1: Build Bass Guitar

Now you start with the build.

  1. Drill out two of the tuners using a 7/64 drill bit. The thickest gauge bass string I used was 0.100 and it just fit through the 7/64th hole. If you have a thicker string you may run into troubles with drilling out the tuner and having enough material left for it to be strong enough to hold the wire. When drilling out the tuner I suggest drilling part way through opposite sides to make the hole smooth and lined up.
  2. Reinstall two of the tuners.
  3. When I looked at the bridge and decided where to put my strings, I thought it would look best if I just used five strings instead of four and put them between the existing six strings. I like the way it looks. I used the 7/64 bit once again.
  4. Measure the width of your nut and using a small file (or nut file if you have one) file your five grooves. Be careful that you don't cut a groove that is too wide or too deep. One of my grooves was too deep and I had to use some JB weld to repair it.

Step 2: Setup and Tuning

Now that the body is ready, it is time for the strings.

  1. Pull all five strings through the bridge.
  2. Put the nut in place and pull your strings through the tuners.
  3. BE CAREFUL - I broke one of my strings by not giving it enough slack and by tuning it too fast. Thankfully I was using a cheap set of strings to practice the set it up before using the D'Addario Strings on the final project. When tightening the top (thickest) string it broke because I didn't have it wound around the tuner before the tension started. I expected it to stretch more, like the Uke strings I am used to. Anyway, the second time, I tightened the tuner more slowly and allowed some slack to wrap around the tuner before the tension started.
  4. I put the top string in 'backwards' so the nut would stay in place.
  5. Tuned to E A D G E.

Have fun with it.