I have a number of CNC related projects for 2024. One of them is a Bass guitar, based on a Fender Precision bass guitar model. I've ordered some HW for the project, it is all arriving slowly in my mailbox, fret wire, bridge, pickups, control HW, etc. etc. I need to figure out wher to get a decent truss rod for this big thing!

This page will slowly evolve over the year, stay tuned!

Below is the current project; Closely inspired from a Fender Precision Bass shape and size. Arm rest and Belly recess as well as the control cavity are my own.

Finally Starting!

I recently bought a bunch of very old rough cut slabs that are blond walnut, cut about 45 years ago and kept in excellent condition. Thickness is between 22 and 30 mm depending on the slabs. I an going to use them mostly for necks I think, and other walnut pieces I have for different projects. I also have some iroko I cut (hard job!) to make guitar bodies, but they turn to be probably too heavy, so I need to revisit my projects for using this nice wood.

Start carving that neck!

I used the design I created (based on P-Bass plans I gathered here and there) to generate the necessary .tap files (containing GCODE for my CNC) so I could launch them one by one with my Mach3 software, using the prepared blank above. It all went well! I used several different fits from ø4mm bits to ø8mm straight and round bits for the curved paths.

The Fretboard

I decided on Oak for the fretboard after watching a Scottish luthier using oak for the fretboard of his guitar, and it looked very nice. I had a leftover big chuck of oak, long enough for a bass fretboard, and cut and prepared two blanks. I also worked on Aspire to create the files for the CNC, and this time promised me to try again cutting the fret slots with the CNC. My last attempt was a complete no-go, I was cutting too fast in too hard a wood for these tiny ø0.6mm bits.
It took a long time, and I was definitely too conservative this time, and didn't want to change the CNC parameters once it successfully started to cut the slots. For Inlays/fret markers, I decided on lateral, elongated 'dots' I probably will cur in a darker wood, such as ebonized walnut, or oak maybe.
The blanks were about 1cm thick, and I used the CNC with a ø35mm planer bit to ensure I got two perfectly flat and parallel surfaces, with a final thickness of 6mm.
The curvature/radius is a compound type, from 9.5" at the headstock to 14" at the heel.

Fret Markers and neck assembly

I Used dark walnut for the fret markers, a quick spin of CNC and the inlays were done to perfectly fit the marker pockets. 

I glued them wit hCA, and a quick 120 grit sanding paper pass. Done!

I then set two small holes in the fretboard to ensure it would stay put as I pressed the clamps to glue the neck and the fretboard, with the truss rod inside. Give it plenty of time to cure and dry...

Laser!

Printing my logo... Still a little bit of issues with/when filling with blacken CA glue. I probably should have been using a higher viscosity one rather than the "thin" stuff. Will try do do better next time. The NEJE max80 laser was set at 40% power, and I use 1 pass on the PM and two passes on the smaller text to get more depth. It burnt the wood on a good 1mm deep, and the edges were just fine.

Wood for the body

I used the services of Hugo Cuvilliez, a renown Luthier in Marsanne, for getting two beautiful pieces of Basswood for the body.  We cut the two pieces needed for the blank out of a big piece of timber, and saw it using Hugo' shot bandsaw. I then took these home for working on the optimal positioning of the body on to of the raw blanks. Later in the week, I'll go back to Hugo' shop to cut and asssemble the two sides into a single blank suitable for my CNC.

Hugo was also kind enough to ensure the two blank halves were perfectly cut, sized, prepared to thickness and square-cut ready for assembly. All this done with his professional tools.... No comparison with my equipment!
Final gluing takes place in my shop.

Setting the frets on the neck

I used my home-made fret bender to set the right curve to the fret wire, cut frets according to the neck slots, hammered them in, tested their seating with a fret rocker, glued them on their side using CA liquid glue (seems more secure in oak wood). The next day, I dressed the frets using a 12" radius dressing jig I made last year, crowned the frets, and finally polished them with steel wool and with a polishing compound with my Dremel tool.

One fine looking neck!

CityCaster series... One big quality step forward...

The first model (a telecaster-like guitar) was carved using the CNC. Quite OK, but very long (6 hours or so) and plenty of opportunity for loosing the sharpness of the maps to the wood fibers, the engraving bit is 'violent" on the wood.
This ime I tried with Laser engraving, burning the wood on 3mm deep with only 60% of laser power. It does take time too... at 1000mm/mn and lots and lots of raster lines, but I find the result... stunning! I'm just at par with the engraving quality of my Dean B. Zelinsky Dellaterra! See below, getting a near 3mm deep engraving in 1 pass!

This is unfinished wood, just out of the laser engraving process and with a little sanding at 120 grit! I'll have to figure out what's best in terms of hardening the wood and finishing it. Probably a good and clear sand sealer, and 2 or 3 very thin coats of hardwax, matte or semi gloss., maybe with a little cream-like tint.

CNC that body!

Time to turn on that CNC and carve the body, It's a simple shape and went well. I did not forget any crucial steps (i.e. zero Z setting after changing a tool bit) and got a very nice result with carving that basswood body. All wood knots have been avoided, leaving me with a very nice bass body. 

I used a 6mm  or was that a 8mm? ¼ round bit and a hand router to go around the body contour on the two sides. A light sanding with 180 grit paper and off to laser engraving.

Note also the change in design in the arm-rest section compared to the "flat & straight" initial design in the simulated model.

Laser Engraving

I had prepared my work with downloading a bitmap map of London, a simple B&W one with quite a level of detailing. I used a specific contour set  from my bass body design, avoiding the bridge, pickups, knobs and the arm-rest section to create a mask and kept only the intersection between the London map and the mask.
I used the mask contour as a line engraving to register my bass body with the laser bed, trying to pinpoint the body as precisely as possible. Next time, I'll embed registration marks done with the CNC in the center pf pickup and neck heel pockets, so I can do this more easily...
With the body correctly in place, it was time to launch an 8h45 engraving job... That's that slow, but the result is so nice!
This officially makes this bass guitar a CityCaster...

Setting the pieces together

That's what I have so far... a great neck that fits the body just perfectly, and a carved body, prep'ed and sanded to 180 grit. All parts seem to fit just fine. I'll have to get strings :-), but before that, A sealant coat is a must, hardening that wood, then I'm thinking of a satin, off-white finish... 3 or 4 thin coats. Same for the neck, except I'll go matte or satin transparent.

As for the electronics, I have an active kit designed for 2 pickups, with balance, volume, bass/mid trebble controls. I'll ditch the balance knob, not needed in my case and the other four knobs.

Drilling holes, Other parts and Test Fitting

The body, the control cavity plate and neck made, it is time to drill all the holes where screws will fit and see how things will be in a near  final assembly state.

I made walnut knobs!; Didn't take long with the CNC and they turned out quite nice. I don't know yet if  I'll use them, but that was a quick experiment. 

After measuring the actual scale length, I may have to move the bridge forward a bit. Looks like I didn't design the part exactly taking the 1st string contact point into account. Not a big issue, there's enough space for that adjustment. I nevertheless ordered a new/slightly different bridge that may provide a little extra adjustment for the poles.

I drilled the bridge to control cavity hole to ground the bridge and strings. A larger hole was drilled to pass the pick-up cables to the control cavity. An even larger one to set the output jack. Then plenty of small ones for all the screws holding pickups, bridge and back cover plate.

Finishing!

Time to do more sanding... Body and neck have been sanded to 400 grit.

I then applied a thin coat of water-based sandsealer, and let it cure for a night, This raises some of the wood grain and additional sanding is required, possibly with an additional coat of sand sealer/sanding to get things really smooth.

I applied a second layer of sandsealer only in the deep areas of the body face, ensuring there was product everywhere. I then used air from an oil-free air compressor to remove the excess, leaving me with sealed grain even in the deep carves.

After everything was dried and sanded, I applied Osmo Poly-X (semi-satin) natural hard oil/wax to the neck and the cover plate. Pictures below show the first coatd applied to the neck; I'm planning on 3 coats minimum...

Body sanding and finishing

With the water sealant fully dried after 3 days, I lightly sanded the body with 400 and 600 grit pads. Fully cleaned the dust with compressed air and I applied a first coat of Poly-X on the body surface,  for a 24h dry time.

Meanwhile, I assembled the HW on the neck after its 3 coats of Poly-X, giving it a very smooth touch. Frets have been cleaned with steel wool, I also started to file the nut (Bone), waiting for string mounting time to set the string slots in the nut.

Body & Neck marking...

Time to set a timestamp and number on these parts. It's my second CityCaster, so #002 it is :-) and it will be final by the end of June or so - 2024/06-002 is the final "serial" number... As if I were running series :-D
This is the body with its 3rd coat of OSMO semi-mate Poly-X

Final assembly and Testing

Assembling all the pieces together was a no-brainer. I just had to set a little shim under the neck Heel to finalise the height of the neck with regards to the bridge. Strings in and here She is. SPLENDID!! to my  eyes at least!

Testing is going well, I'm not a bass player so it's kind of hard for me to tell whether this is a great instrument or not, but I'll get friends who are bass players to help me with the best settings. So not only it will be a great looking instrument, but it will be easy to play too :-)

My first test here: https://youtu.be/ZZYcBS9Rw6Q

The Final touch

I had to try....

I ordered and [finally] received the typical reinforcement steel plates with a thin electrolytic coad of copper+chrome that can be found at the back of the body to support the neck-body assembly screws. But how to engrave a logo on these?
I tested with the laser engraver and if it indeed marks the plate (running 3 passes at 90% power and 10mm/minute, the result is visible, but not 'deep' engraved. I could continue with more passes, but it's not the best for this laser and would then take a lot of time. 

So a maybe simpler logo design with the CNC? For this test, I used a ø0.6mm end-mill bit, and was cautious as to not move or plunge too fast, which for sure would break bits. I used WD40 as local lubricant and was pleased at the quality of the result, and found correct parameters quickly. Now, there's my signature on the guitar back plate. Love that!