Do CNC guitars dream of electric sheep?

[komodo]

Love everything about this.

[curtisa]

15 hours ago, ScottR said:

Hold on to it tightly or it might just float away.

If I drill a hole into it and inhale the air trapped inside, will my voice get all high and squeaky?

[curtisa]

14 hours ago, komodo said:

Love everything about this.

Stop it, you big tease

I'm feeling like the hands-off nature of this build is somewhat cheating the system in comparison to yours.

[Andyjr1515]

On 2/19/2020 at 10:16 AM, curtisa said:

Time for a wee break from proceedings. The lack of a headstock means any logo I apply needs to go elsewhere on the instrument. The common spot for these headless instruments appears to be just above the neck near the neck pickup and bass-side cutaway. I've seen seen this done as plain engraving (Strandberg) and a decal (Kiesel, Steinberger). I'm going to match this location for the logo, but but I'm going to go for something a bit more wanky in presentation and do some V-carving.

First, some volunteers from the audience. Here's some dark Blackwood and Eucalyptus from the offcuts bin to experiment with a bit:

Step 1 is to engrave the design into the Eucalyptus using a vee bit. It's important that a tapered bit of some kind is used for this operation:

In the Blackwood the mirror image of the design is embossed into the surface with the same vee bit, giving a kind of paper stamp effect. The vee bit ensures that the peaks of the embossing remain crisp and sharp. Each corner of the letters' stroke has a prismatic effect:

After separating the Blackwood mirror from the block the two pieces can be married up:

After a few hours glued up in clamps the excess Blackwood can be planed and sanded down:

Because of the use of prismatic carving, much finer detail can be obtained than by inlaying into channels with vertical sides. With regular engraving the finest detail you can do is limited by the radius of the smallest cutter you have on hand. The only drawback to this technique is that it only works on flat surfaces, If the inlay is sanded back unevenly (eg, on a radiused fret board), the thickness of each of the strokes vary as more or less of the prismatic inlay is exposed.

A bit of danish oil brings out the true effect of the contrast. The whole logo here is only 8mm x 60mm:

 

I've never not ever seen that done like that before.  Stunning!  

[komodo]

4 hours ago, curtisa said:

Stop it, you big tease

I'm feeling like the hands-off nature of this build is somewhat cheating the system in comparison to yours.

nonsense. We both know just how much time it takes to program and setup CNC, it's no less work, just different. Plus there's still have plenty of hand work to do.

I was within a hair of picking up a turnkey CNC off FB marketplace last week, but didn't have the spare 2k or whatever they were asking, OR any space to put it. Then it was gone before I could give it a second thought. Being able to reproduce them after the work of program/setup is very alluring, and probably required to make any kind of business out of doing this. 

[ScottR]

8 hours ago, curtisa said:

If I drill a hole into it and inhale the air trapped inside, will my voice get all high and squeaky?

Good call! Try it and see.

4 hours ago, Andyjr1515 said:

I've never not ever seen that done like that before.  Stunning!  

I forgot to mention how much I likes that logo. When I got to it I said to myself-that's quite awesome, it is. Then I kept on reading through your picture dump and that thought got chased out by the next one......

SR

[curtisa]

16 hours ago, komodo said:

Being able to reproduce them after the work of program/setup is very alluring, and probably required to make any kind of business out of doing this. 

Yes, that is certainly a big attraction to this whole process. It might be a lot of messing around to get it going from scratch, and even now having made the first run of cuts on the machine I'm finding myself still going back to the 3D model and refining it further, but the repeatability and speed at which subsequent builds could take shape is a big plus. Even just ditching the current pickup configuration in favour of a HSH or HH is only a relatively minor revision to the model and subsequent code, as the bulk of the work remains the same.

[curtisa]

12 hours ago, ScottR said:

I forgot to mention how much I likes that logo. When I got to it I said to myself-that's quite awesome, it is. Then I kept on reading through your picture dump and that thought got chased out by the next one......

Thanks Scott, glad you like it. I was aiming for simplicity when I chose it, plus I always liked those 80s open-ended Tron-style fonts. 

That's the trouble with a lot of us builders here at ProjectGuitar - always distracted by another shiny thing.

Ooo look, a squirrel...

[curtisa]

17 hours ago, Andyjr1515 said:

I've never not ever seen that done like that before.  Stunning!  

Cheers Andy. I take it your double-negative/single positive was confirmation that you had in fact hadn't not unseen that method before again, and are unlikely to not ever see it again before you didn't see it the last time?

[Andyjr1515]

2 hours ago, curtisa said:

Cheers Andy. I take it your double-negative/single positive was confirmation that you had in fact hadn't not unseen that method before again, and are unlikely to not ever see it again before you didn't see it the last time?

Without no doubt you are not wrong, Andrew.

You can't not beat the Queen's English, me old cockle-shell mate! 

[curtisa]

22 hours ago, Andyjr1515 said:

You can't not beat the Queen's English, me old cockle-shell mate! 

Any grammatical faux pas, quirks and foibles I blame solely on my convict heritage.

[curtisa]

A few minutes in the router table cleans up the remainder of the body outline. If I were to do this again I'd let the CNC do the full profile on both halves of the body and then glue them together as prefabricated pieces. Now that I know that the machined alignment pin method for the top and back gives me good results, I feel pretty comfortable that I wouldn't need to stress about the two halves lining up badly if they're pre-shaped before gluing. The top is only 15mm thick and the blank is 35mm, which makes the machining of them as two separate entities quite achievable with the longest endmill I have in my collection:

Shaping the heel is something that could easily have been done on the CNC, but I was struggling with a way of modeling it in the software. So to keep the ball rolling and just get the job done it's back to the handtools. 5 minutes with the saw rasp vs several hours of faffing around with a 3D model, there's obviously no contest. Maybe next time, however...:

By necessity the output jack is a job for the drill press, as there's no way this would fit on the machine given the body has to be held upright pointing up at a 45degree angle:

Then it's back on to the machine to recreate the earlier inlay test on the real deal. The pencilled rectangle marks the nominal bounding box of the logo:

The first pass of the vee bit leaves the surface somewhat scruffy looking, but there are more cleanup passes required to get rid of all the excess material between each of the prismatic inlay pieces. Note also that the inlay is the negative of the inlay channels cut into the body:

The tip of the vee bit is used to clean up the super-fine corners, which reveals a little bit more detail in the lettering:

And a 0.8mm flat endmill is used to get rid of the remainder of the excess and leave behind nothing more than the embossed inlay sitting in a 'tray':

Once the embossed inlay is cut free from the surrounding timber it can be 'plugged' into the inlay channels and glued up. This is actually the second attempt at the prismatic inlay piece, as the first one wasn't machined deep enough. With the 'peaks' of the inlay too shallow for the cuts the whole inlay could slop around in the inlay pockets, which would have left a dark glue shadow around the edges of the letters:

[Guest]

I'm no CNC or headless guy, but that is some super work

[curtisa]

Just a brief update today. Finally had a chance to release the clamps and trim the excess off the inlay:

Little by little...:

[ScottR]

It's magic!

SR

And when I blinked I still saw the logo imprinted on the inside of my eyelids..

sr

[curtisa]

This headstocklet needs a cover plate, so after rifling through the scraps bin I found an offcut from the body top. Always pays to keep even the smallest fragment of your fancy woods for builds like these. A quick trip to the bandsaw and a few passes under the drum sander yields a 2mm thin sliver of eucalyptus that can be overlaid onto the headstock of the neck:

The tricky thing about working with such small pieces is devising a method to clamp it while it glues. There's a chunky bit of clear plexiglass acting as a clamping caul over the biggest flat area of the headplate, and under the rear two clamps I have a couple of brass PCB standoffs perched perilously on the edges adjacent to the nut slot. I guess if I were doing this on a production level I'd make up some kind of custom-shaped clamping caul out of HDPE that fits around the end of the fretboard:

The finished article. Oh, and frets already in, sorry. I've decided to take the bull by the horns on this build and install stainless steel jumbos after swearing blind I'd never work with stainless again. Wasn't actually as bad as I remember it being the last time, so either I've remebered it wrong or I'm more tolerant of the experience. Zero fret yet to be installed:

Side markers (yes, they are there. They're just a bit smaller than usual - 1.5mm diameter this time):

First coats of oil. The redheart sapwood of the leatherwood is finally starting to stand out a bit better at the edges of the body:

[ScottR]

10 hours ago, curtisa said:

First coats of oil.

If the first coats of oil are not as good as sex, they are certainly as good as foreplay.

SR

[curtisa]

Yes, this build is still alive. Just waiting for the finishing regime to dry properly in this autumnal air that's now starting to cool off a bit more than expected.

Time to start checking the fit of some of the key components. First I need to add an extra wiring channel (if I'd planned this better I would've added it in while machining the body:

 

In the absence of using shielded wire for the single coils, twisting the pickup leads makes them a bit less susceptible to the effects of external hums and interference. Chucking the two wires up in the cordless drill is (surely?) the oldest trick in the book for this?:

 

Couldn't resist a quick dry assembly to see how it will look:

 

First problem: the Oak Grigsby 5-way switch I bought for this project is too tall to fit in the cavity without bottoming-out on the control cover, so I'm having to order a low-profile Gotoh 5-way switch which will delay things a bit.

Second problem: I need a way to mount the individual headless string locks that doesn't involve passing a mounting screw through the truss rod access at the end of the neck. If I just mount the D and G string locks direct to the end of the neck using the provided wood screws, the screw holes fall pretty much inline with the truss rod access hole. Not good.  So it's back to the computer and CNC to come up with a mounting adaptor plate to allow me to install the string locks without encroaching on the truss rod access:

 

After cutting the plate free of the aluminium (or aluminum, if you prefer), and cleaning up the surfaces and edges a bit I get this. The six larger holes are tapped for an M3 thread to secure each string lock while the six smaller holes are designed to accept the tiny metal pins cast into the underneath of each string lock, which help stop them swiveling around as the string locking screws are tightened up. The two countersunk holes provide an easy attachment point for the mounting plate into the headstock spaced far enough apart to avoid punching through to the truss rod access:

 

Dry run:

The plate itself will be spray painted black and then recessed into the headstock to provide the correct amount of downward force the strings require as they pass over the nut.  

[ScottR]

Lovely work and a useful tool you have there. Brett calls his RoboRad, what do you call yours?

SR

[curtisa]

The General.

 

 

 

 

 

 

 

 

General Dissaray.

[Andyjr1515]

Beautiful job, Andrew.

Andy

[komodo]

That’s glorious! It’s great to see how you are using the machining to take everything next level. Can you cut pearl with the cnc? Seems like holding the material would be a hurdle.

[curtisa]

You can get cutters designed to work with natural shell, but I've not tried it myself (yet). I imagine cutting coolant would also be required, which increases the messiness factor considerably.

I've no idea how you'd secure such tiny pieces while machining them. I guess you could mill some tabs into each piece so that they have something larger to 'hang on' to. After machining you cut them free and clean the edges up by hand (see my previous thread update, above).

[curtisa]

Work continues at a snails pace.

The string lock assembly needs to sit a bit lower on the headstock to provide the strings a chance to deflect downwards after clearing the zero fret, so the mounting plate gets recessed into the headplate immediately behind the nut ledge:

The hair-thin film of dried Titebond over the trussrod route that the CNC machining reveals is a nice touch :

The strings also need a bit of clearance underneath them as they head downhill from the nut to the string locks, so a gentle bit of manipulation of the end of the fretboard is required, The ramp is just added with the use of a small chisel and a bit of finessing with sandpaper:

Then it's time to give the string lock adapter plate a quick assemble to see how everything lines up:

Note also the installation of the zero fret and nut. I had to stone away the barbs on the fret tang a bit so that the fret was only a firm press fit into the slot. If it had been just a regular fret hammered in it would have likely split the thin piece of timber between it and the nut as it squeezed into the slot. The beauty of using a zero fret is that the nut only has to set the string spacing. String height is governed by the zero fret itself, so I can be as rough as guts with cutting the nut slots - they just need to be deep enough to allow the string to head in a downward trajectory after clearing the crown of the zero fret. In the spirit of the cheap(ish) nature of this build, the nut here is just a cheap plastic pre-cut nut from Aliexpress that cost all of about 75 cents. The slots already cut into the nut just serve as markers for where I need to start filing away hammer and tongs to deepen them enough to just guide the strings down over the zero fret.   

Then it's time to do my least favourite operation of this whole guitar making malarkey - crowning and polishing. The only enjoyable aspect of this I find is peeling off the tape at the end :

Here's something unexpected I hadn't planned for that took me completely by surprise. After the above point I figured it would be a good idea to quickly string it up to see how everything aligned and sat. The problem I came up against was that I could only just get the floating headless trem to balance, even with all 5 springs installed and the trem claw maxed out. Measuring the length of the springs and the amount of stretch they were under compared to another Floyd Rose install I have here revealed no obvious discrepancies that I could account for.

The difference with a headless trem (that I hadn't accounted for) is that the string anchoring point in the saddle is a lot further back than a Floyd or traditional Strat-type tremolo. In a Floyd/Strat the leveraging point of the string is pretty much right at the saddle. In a headless trem the string ball end sits inside the tuner screw assembly 2 or more inches further back from the saddle. Consequently the extra horizontal length behind the saddle allows the string to exert more levering force on the trem to counteract the springs, and thus requires more tension in the springs to pull the trem back to equilibrium.

The upshot of this rather annoying discovery is that I've had to extend the tremolo spring cavity another 20mm closer to the neck to get me more stretch on the springs. It will look fine once finished and a cover installed, but it's a frustrating setback nonetheless:

Which unfortunately means this thing is now scrap as well, as it is now 20mm too short:

[ScottR]

Good thing you did a test stringing...

SR