3 Guitars Made From a Table. #3 the Jazz Bass

I wanted to make an electric bass guitar using hard wood.
Wood that has been drying long enough not to twist anymore.
A whole-wood table plate sounded perfect for this.
I found an old one, made of birch, for free on the internet, I only had to fetch it and say thank you. Brilliant.
It turned out this gave me material enough to make 3 guitars.

This is the third one, the jazz bass.

Supplies

Here is the parts I used, they all have a wide variety of alternatives, but these worked well for me.
Strings: Ernie Balls Super Slinky Roundwound 45 65 80 100 gauge 30$
Bridge: No brand ebay 13$
Nut: Tusq graph tech nut Jazz Bass 4 string 10$
Pickups: Wilkinson Neck & Bridge set for Jazz Bass 35$
Control panel: No brand ebay wired switch control plate for Fender Jazz Bass 7$
Frets: No brand ebay 2.9mm set for bass, 2 sets of 21, giving just enough long ones to fit 24 frets on the neck. 18$
Fretboard inlays: Guitars and Woods 3$
Tuners: No brand 4 left ebay 18$
Guitar strap: No brand ebay 4$
2 Strap mount scews: No brand ebay 2$
Truss rod: 600mm two way no brand 8$
Tools: Fret crowning file 5$, small rubber fret hammer 5$, Guitars and woods 9.5" radius sanding block 13$

Step 1: The Table

Made of solid birch, the table is the base of a sturdy bass guitar.
Not thick enough, so it must be cut and glued together.
The old lacquer needs to go, I chose to remove it by sanding.
Doing this in your living room, like I did, can initiate objections, but one of us is not married, so I could carry on.
Use a dust mask and a dust collector when doing this, the lacquer dust is far from healthy.
I forgot, and the symptoms coming from my lungs could easily be misread as pandemic.
I bought dust masks, and attached my vacuum cleaner close to the sander, much better.
When the surfaces was prepared for lamination, I added a generous layer of wood glue on both sides, before pressing them together with something heavy. In my case, a heavy wooden chair and my self.

When the plates were dry, I could start drawing the shape I wanted.
First, draw a center line, everything is related to that, make sure it is not erased until you have positioned everything.
My inspiration has been Z-body jazz basses, and I tried to draw it around a beautiful pattern I found on the underside of the table.
I drew strings and frets for a 86cm scale (distance between nut and bridge, the part of the string that vibrates).

Step 2: Body Cavities

When I got the pickups I wanted to use, I found that they could be placed at an angle to be positioned perfectly related to the strings, at the distance I envisioned from the bridge.

I started making cavities for the pickups by drilling holes to the depth I thought the pickups should be.
Then I used a knife to remove the excess wood, realizing quite soon that a chisel is way more precise and effective.

Step 3: Body Shape

After some redesigning and decision making, I could start to cut the main shape of the body.
I do not have a band saw, so I drilled large number of holes in the blank and cut with a handsaw where appropriate.
A considerable amount of filing, rasping and planing gave a rough outline of the body, and I started shaping the other dimensions.
The thickness was roughly 10mm too thick, so I removed that with a machine planer.
Making the back surface even was hard with a sander, but when the handle fell off my wood file, I discovered that it was perfect to make a perfectly even flat surface.

Step 4: The Neck

I wanted to try to make an 11° scarf joint, and figured I needed to make a jig for that.
Some trigonometry calculations gave me the cut I needed to make my 11° jig;
38mm width / sinus(11°) = 200mm.

The neck is made up of 2 layers, with a separate head.
All 3 parts were cut with the same angle.
I added a groove in the top part, to insert a truss rod before gluing it all together.
I glued the top part to the head first.
The head rotated a bit in the irreversible gluing process, making me have to rotate the lower piece correspondingly. Luckily I had plenty of excess material to work with, so I could carry on.
The truss rod was inserted and the bottom piece glued to the rest.
The result was less than perfect, it was hard to get the pressure right, and the glue layer became a bit thick.
A better way would have been to glue the 2 neck pieces first, plane the angle thoroughly and glue the head on last.

The neck thickness I aimed for was 23mm at fret 1 increasing to 27mm.
I started with a symmetric U-shape, thinking I want to try it a while before I remove more material when I know what shape feels best.
The top of the neck was sanded with a sanding block with a radius of 9.5", for a slightly curved fretboard.
I could then follow the strings down the head, to see where I should place the tuners.

Step 5: Neck to Body Joint

Using the center line, and the center of the neck, I could mark the neck shape on the body and carve out a neck pocket.
I could also mark the exact position of the bridge.
Finally I could sand the rest of the lacquer off, needing the center line no more.
Now I could see the wood grains and start to see the finished product.

Step 6: Finish the Neck Shape

Having verified the geometry of everything fits, I could now remove the last bit of the width and thickness of the neck.
I used a long straight tool to sand the edges straight, and a planer to get to the thickness I wanted.
A lot of filing and sanding to get the curved shape, led to a test fit and I could compare it to the bass I made out of a ski.
Looks a bit more like a normal bass, this one.

Step 7: Fret Board Inlays

6 mm acrylic inlays was whacked in place in 6mm predrilled holes with wood glue in.

A quick sanding with the curved sanding block, and the inlays looked like they had always been there.

Step 8: Fret Work

Using Monsterbass fretcalculator https://www.monsterbass.nl/fretcalc.php I marked the fret positions on both sides of the neck.
If you want to make one yourself, this is the formula:
position = s - (s * cx) (s minus s times c to the power of x)
x = {1, 2, 3, 4, 5, ..., 24} (if you want 24 frets)
c = 0.9438743127
s = the scale length (distance from nut to bridge, this guitar has a scale of 86cm)

I could then cut a slot for the frets and hammer them in.
My frets had a larger radius than the neck, making them want to rise on the ends.
The slots I had cut was not tight enough to prevent that, so I decided to superglue them in place, one side at the time, pressing them all the way in.
The result was a little less successful than I hoped, so there was need for quite a bit of fret work.
The frets that was sticking out was filed down independently, before the whole fretboard was sanded with the curved sanding block.
A fret crowning file is used to get the frets shape back.
I made wood filler by mixing wood glue and saw dust to fill the gaps in the ends of the fret, if not the frets would have been sharp against the fingers when playing.

Step 9: Protective Finish

I used linseed oil to protect the wood.
It makes the wood darker, and brings out the wood grain

Step 10: Electronics

The first attempt is to see how it sounds without shielding the cavities.
I might go back and do that if it is noisy.
I had a pre-mounted control panel, which meant I only had to solder the pickups ground wires to the back of the volume potentiometers, and the positive wires to the right lug.
There was also a ground wire I threaded up a hole to the bridge.
I glued it in place, with the end of the wire sticking into one of the screw holes of the bridge.

Step 11: Mount the Strings and Fine Tuning

According to an instructional video provided by Fender, I learned that these kind of tuners are best wound by first cutting the string to a length that is approximately the length of 2 times the distance between two tuners longer than the tuner. So I cut them about 9cm longer than to the tuners, put the end into the tuner and held the string tight while winding the tuners.

The result is as expected, with strings far from the frets, both at the nut and the bridge, hard to play on, so the adjustments can start.
I loosened the strings a bit, lowered the bridge all the way down and tightened the truss rod quite a bit.

The nut had to be sanded down to be able to comfortably play the first fret.
But the neck and the nut has a curve, and my sanding block is curved the opposite way.
I had to create a mirrored sanding block, by sanding a wooden block with my original.
I then wrapped the new sanding block with sand paper, fastened it to my work bench, and could sand almost 2mm of the curved nut.
I hade made a mark on the nut with a caliper, to avoid sanding too far.
Now all the frets are easily played, and only one fret is buzzing on one of the strings.
That one needs a tiny bit more filing, and it looks like I managed to save a neck that threatened to make me start the neck all over.