One piece black walnut crotch headless 6 string

[Jeff Siddall]

Cut your slab down closer to the template, seal the edges and wrap the whole thing in saran warp to slow the drying. Took me 4-5 years to bring a slab of ebony down to a workable size but maple should be quicker.

Done. I cut the board about 4" longer than I needed and immediately (within a few minutes) sealed the ends with paraffin then wrapped the whole thing in cling film. I also weighed all the pieces, including the two offcuts, to check for stability. When the weight of the offcuts stops changing then I can start monitoring the large piece. If I calculate an accurate density of the offcuts once they are stable then I should be able to predict the final weight of the large piece once it is dry too to give me an idea when it reaches EMC.

One other thing: no sign of honeycombing so far. I was a bit worried there could be structural issues given the cracks and checking but so far so good.

Got it. One thought is that if you're putting tow in the bottom, might it be a good idea to rout the slots with a 1/4" round nose bit? Avoid the sharp corners and slightly reduce the chance of a sand through(?) Would only work if you put in 1/8" or more depth in the form of tow so the carbon bar stock would stay above the radius. Hope that makes sense.

Anyway I am eager to see how it turns out. Bruce has made a lot of converts I suspect, including me, with his ultra clear discourse on the tow method he uses. I'm planning to try it out next time myself, on bass #3 or #4, both of which are on hold at the moment.

To be clear, there will be no CF bars here. The whole slot will be filled with CF tow. Due to the thickness I am trying to achieve there really isn't room to put CF below the truss rod so it is all going beside.

Still, round bottom slots would be a good idea. I have a 1/4" ball nose mill for my CNC but don't think it is deep enough to fit my palm router. I hadn't planned to do these slots on the CNC but maybe that would be the best idea.

Plus 1 on using round bits. I finish all my truss rod slots with a round bit.

Yes, I agree, that is a good idea, although ideally the end blocks should be square bottom and the center rod section round. Not that I couldn't do that if I decided to get fancy.

 

[Slidlow]

To be clear, there will be no CF bars here. The whole slot will be filled with CF tow.

I get the tow idea when placed under the trussrod but don't believe it is of value beside the rod. Actual CF rods are made with heat and pressure and are more dense then hand laid up tow so would have much more strength and resistance to flexing and bending. I would expect formed bars to be inherently better and would be my choice to stabilize the neck.

 

[Jeff Siddall]

CF tow is just unwoven CF. Admittedly hand laid is going to be less perfect than pulltruded, but I will use a 1/4" wide edge to press the wet tow into the channels so it will be pretty dense. I also have plenty of it and I can make it the ideal dimensions so I am not worried about strength. I am actually more worried that I may end up making it too stiff.

 

[Jeff Siddall]

Having finished my CNC, and a script to generate cut files to make them, I finally finished the fretboard for this build today:

This is a 9.5" radius at the nut and 28.5" at the bridge and was surfaced in [substantial] 183 passes. Took over an hour but with 0.5 mm or less pass spacing there is very little sanding to be done to finish it.

This still needs to be freed from the blank on a saw and then side/face dotted/slotted (depending on whether I install fretboard LEDs) sanded, fretted, and eventually attached to the "one piece" but I am really happy with how the board has turned out so far.

 

[Max Bogosity]

Random thought: There isn’t going to be much walnut left in that neck by the time you add all the reinforcement, and it won’t be visible from the front anyway. What if you did a one piece body and fingerboard instead? Make the neck shaft from another more stable wood, glue it into a slot in the back of the blank while still square, then carve away everything that isn’t a neck or body.

 

[Jeff Siddall]

Random thought: There isn’t going to be much walnut left in that neck by the time you add all the reinforcement, and it won’t be visible from the front anyway. What if you did a one piece body and fingerboard instead? Make the neck shaft from another more stable wood, glue it into a slot in the back of the blank while still square, then carve away everything that isn’t a neck or body.

That's an interesting idea, and I already have a variant of that planned for my "Tamahawk" two-piece piccolo build. On that one the fretboard and top will be one piece, and the body and neck will be another. But for this one I kinda want to stick with my original goal that everything you see is from a single slab. I guess if it all goes wrong I can still cut off the neck and make a new bolt-on/set neck, then cover it with a walnut fretboard from "the one piece".

 

[Jeff Siddall]

Next up: if you are going to make a bass from a single slab of wood there is no getting around making your own wood knobs. Having never done any knobs before I did a bit of thinking about what I wanted, then a lot more thinking about how I would actually make them, and came up with a script to cut them on the CNC. I took inspiration from domed, hats and fluted knobs and came up with this:

It is familiar for sure, but I don't think I have seen any wood knobs like this before.

It has 6 grooves, inspired by this being a 6 string, but also because I liked the look. I also tried a 5 groove version and it looks OK too, so maybe I will do that on my 5 string build.

I designed the code to cut the marker dot and side grooves after the roughing passes but before the finishing pass. That means I could paint/stain the marker and grooves a different color, then cut off any overpaint in the finishing pass. Next step: fire up the CNC and test to see if it actually works!

 

[Slidlow]

Next up: if you are going to make a bass from a single slab of wood there is no getting around making your own wood knobs. Having never done any knobs before I did a bit of thinking about what I wanted, then a lot more thinking about how I would actually make them, and came up with a script to cut them on the CNC. I took inspiration from domed, hats and fluted knobs and came up with this:
View attachment 4598472

It is familiar for sure, but I don't think I have seen any wood knobs like this before.

It has 6 grooves, inspired by this being a 6 string, but also because I liked the look. I also tried a 5 groove version and it looks OK too, so maybe I will do that on my 5 string build.

I designed the code to cut the marker dot and side grooves after the roughing passes but before the finishing pass. That means I could paint/stain the marker and grooves a different color, then cut off any overpaint in the finishing pass. Next step: fire up the CNC and test to see if it actually works!

I could see me making some like that in ebony. Hmmmmm.

 

[Jeff Siddall]

A few hours of tweaking, and a hunk of scrap curly maple, and a quick rub with some 220 and tung oil, and I had this:

I took a Sharpie to the dot on the top and one of the grooves on the side on the knob in the front as a test. I think some transparent dye instead of the Sharpie, plus sufficient time to actually dry before moving on with carving (you can see some smudging on the dot), and that could look pretty good also.

They are a bit fiddly, and each one takes about 20 minutes to carve, and I still need to install the grub screw and drill the hole in the bottom, but I think these will do nicely. I was pleasantly surprised how close to the render they came out of the CNC

Also, next time I will make sure to screw/clamp the board down in at least a two places. One screw and some double sided tape weren't ready for this, as evidenced by the demolished knob on the left when it shifted:

 

[Beej]

Those look great!

 

[Slidlow]

A few hours of tweaking, and a hunk of scrap curly maple, and a quick rub with some 220 and tung oil, and I had this:
View attachment 4598956

View attachment 4598957

I took a Sharpie to the dot on the top and one of the grooves on the side on the knob in the front as a test. I think some transparent dye instead of the Sharpie, plus sufficient time to actually dry before moving on with carving (you can see some smudging on the dot), and that could look pretty good also.

They are a bit fiddly, and each one takes about 20 minutes to carve, and I still need to install the grub screw and drill the hole in the bottom, but I think these will do nicely. I was pleasantly surprised how close to the render they came out of the CNC

Also, next time I will make sure to screw/clamp the board down in at least a two places. One screw and some double sided tape weren't ready for this, as evidenced by the demolished knob on the left when it shifted:
View attachment 4598954

Could this be performed on an ebony dowel?

 

[Jeff Siddall]

Could this be performed on an ebony dowel?

Sure! You would just need a way to hold the dowel in place, but that could be as simple as a piece of 2x4 with a dowel-sized hole drilled in it.

FWIW: the knobs above are a pretty traditional 19 mm diameter on the fluted part, with a wider base (like hats use) that is 24.4 mm diameter. But because the script I wrote is parametric it's just a matter of specifying the new dimensions and a few milliseconds later there is new G-code to make it. Here is a variant I just tried with a 19 mm base and 12.7 mm fluted section, that has the 5 flutes like I was considering for my 5 string, and I kinda like it:

 

[Level5wizard]

This is going to look great

 

[Jeff Siddall]

Now that the knobs are taken care of might as well head onto pickup covers. For this bass I think I will build some sidewinders, and those need a P4 size cover. It sounded simple to come up with a script for cutting out soapbars, but as with anything CNC it is always takes more time than expected. Many hours later I ended up with this:

Note: the render shows the countersink on the bottom corner because it isn't aware of all the flipping and aligning going on in real life.

Part of the reason for the longer development time was that the one job does everything on the cover: inside cavity, outside shell sides, screw holes, which required a drilling operation that I had never tried before, and countersinks. Since the countersinks are on the top of the cover, and everything else on the bottom, I needed to halt the job to allow the covers to be flipped over before continuing with the countersinks. That meant also coming up with a way to align the countersink holes exactly over the screw hole. I landed on a process that uses the countersink bit itself as an alignment pin in the screw holes. This actually worked quite well on the covers for my 5 string build if you want to see some finished examples.

The other thing that took extra time was figuring out why the CNC was throwing errors when cutting the corner arcs. I traced that problem to python 3 doing rounding in a way that would cause a grade 2 student to fail their math test. This is AKA "round half to even" and is apparently compliant with IEEE 754, but neither I nor the CNC were amused.

Once I finish cutting the covers for this build I will post some pictures of those too.

 

[Jeff Siddall]

The knobs will need a grub screw to hold them in place. Since I didn't really want to use inserts I decided to try cutting tiny M3 (about 7/64" diameter) threads directly into the wood. I had a scrap of wenge from the pickup covers so I drilled and tapped it and the resulting threads look unbelievably clean:

I should be able to use a 5 or 6 mm long grub screw so there doesn't seem to be any need to worry about the threads getting stripped out.

Next job: figure out how to chuck a 19 mm diameter knob into my 1/2" drill press to drill the hole in the bottom concentric to the knob.

Ideas?

 

[RichterScale]

Not sure about the knobs, but you can wick some thin CA into those threads and then run the tap through again after it's cured. Just a little insurance.

 

[RichterScale]

I wanna say it was @dwizum that made knobs in his drill press?

 

[Matt Liebenau]

+1 on the CA in the threads. I’ve done it on many knobs and it works great.

 

[RichterScale]

Next job: figure out how to chuck a 19 mm diameter knob into my 1/2" drill press to drill the hole in the bottom concentric to the knob.

Ideas?

I completely misread this.
What if you take a block, drill a 19mm or 3/4" hole in it, then saw it in half, then put it in a clamp and squeeze it back together with the knob in it?
Maybe use a softer wood like pine.
Or even a drop of hot glue before clamping.

 

[Jeff Siddall]

I completely misread this.
What if you take a block, drill a 19mm or 3/4" hole in it, then saw it in half, then put it in a clamp and squeeze it back together with the knob in it?
Maybe use a softer wood like pine.
Or even a drop of hot glue before clamping.

Yes, that would clamp the knob, then how would I chuck the block into the drill press? To get a concentric hole requires spinning the knob and holding the bit stationary rather than the other way around. Ideally I would use the lathe that I don't have!