Thinking of building an acoustic ---> It's done!

Misterg

I futzed with the neck joint a bit more and got the angle a bit closer, but I wanted to leave the final setting until I had attached the fingerboard and installed the frets.

I had a piece of ebony for the fingerboard and was originally intending to rip a couple of slices off it to create an "invisible" binding to hide the fret ends. However, following the experience with the headstock inlay, I started wondering if I could also cut blind fret slots with CNC. It turns out that quite a few people do just that.

A few experiments gave me enough confidence to go the whole hog and try and machine the entire fretboard on the CNC: radius, fret slots, inlay pockets and profile. I don't feel too bad about that as I've previously cut fret slots by hand (on my Tele & uke) and sanded a radius into an ebony fretboard (on my Firebird - not an experience I'm keen on repeating; it took a loooong time) - so I feel I've served my time there.

With the neck temporarily attached, I could confirm the finished length of the fingerboard to match up with the sound hole and do the CAD/CAM. My CNC isn't big enough to do the whole fretboard in one setup, so I mounted the blank on a backing board that could be indexed to machine the whole thing in two setups without losing position. A test run on plywood came out great, so there was nothing for it but to try the ebony.

Roughing out the radius:

Finishing the radius:

Machining the fret slots:

All machining done:

I'd bought some 'diamond and square' MOP fret markers to use, but now thought that I could add a more original 12th fret inlay. I had learned from my experience with the headstock inlay that the shape of the inlay pockets needed to be tweaked to make sure that the tool got to every corner of the pocket, even if it meant over-cutting slightly. You might be able to see that the corners of the pockets for the 'squares' have got a little bite out of them to ensure the pocket is big enough without enlarging it all around:

The 12th fret inlay was a bit of an experiment. I machined the shell pieces first and was amazed that the narrow parts could be cut without breaking:

Just dry fitted:

I glued the inlays in with CA glue and some ebony dust. After a bit of sanding, it came out better than I could ever have hoped:

I couldn't resist mocking things up:

If I can manage to finish it without messing up, I think it will look sweet.

Happy New Year to anyone who has made it this far!

fastonebaz

Those fretboard inlays are splendid,  so intricate.  

SteveF

Brilliant.  Love the 12th fret inlay!

Misterg

fastonebaz said:

Those fretboard inlays are splendid,  so intricate.  

Thank you! I'm really chuffed with how they came out.

Jez6345789

Awesome work looking forward to the last bits and it deserves a short video interesting to hear how it sounds great work

Misterg

Jez6345789 said:

Awesome work looking forward to the last bits and it deserves a short video interesting to hear how it sounds great work

Thank you - I will definitely video the stringing up as at least I might get my £250 for the video if it collapses into a folded mess of sticks

Things slowed down a bit over the Christmas holiday, but I got a few bits done:

I lined up the fingerboard and the neck blank and put a couple of locating pins in under the 1st & 10th frets. I could then trim the neck blank a bit closer (I think this might have already been done in that last pictures of the previous post).

I messed with the neck joint some more now that the neck was nearer it's final shape; "flossing" the joint with sandpaper to adjust the angle.  For some reason, I wasn't getting the results I was expecting - the more I sanded, the bigger the gap got... It took far longer than it should for me to realise that the tenon was bottoming out on the body (Doh!). With a couple of mm trimmed off the tenon, normal service was resumed. I stopped with the neck angle a couple of mm off the top (without the fingerboard). I believe that this is at the low end of what is acceptable but I think it's easier to raise it after the fingerboard is glued on than to lower it. Final angle can wait until the fretted fingerboard is installed & the bridge is available.

I fretted the fingerboard before glueing it to the neck. The fret wire has slightly thicker than 'normal' tangs and proved a good, tight fit for the CNC cut 0.6mm slots. Fret tangs were cut off to clear the end of the blind slots with the ubiquitous modified sheet metal nibbler:

I have a small, soft faced mallet that I've used previously for fretwork, but it lacks 'heft' and tends to kink the frets. A bit of leather glued to a body hammer worked much better this time (practice shots):

There was only the smallest amount of back-bow on the fingerboard after it was fretted - not enough to cause me any concern whatsoever. (The 1st & 10th fret will be fitted after glueing)

(The fret ends haven't been attended to yet)

I glued the fingerboard to the neck, and trimmed the neck flush with it using the router table.

Then set about carving the back of it to shape:

Still very much a work in progress. As with my previous attempts, I find that if l put it to one side for a few days and then to pick it up with fresh hands, I find a few more bits that need some work.

I'd also been looking at options for cutting the binding channels - I have a small trim router (Katsu Makita copy) so was looking for the best way to use this. I've pinned my hopes on the style with a 'bobbin' guide that runs on the side of the guitar (a bit like the Elevate binding jig).

A bit of CAD, some CNC and some anodising and I have a jig:

(Sorry about the metalwork content!)

fastonebaz

I like how you made a "J" for Jig   awesome

Misterg

fastonebaz said:

I like how you made a "J" for Jig

Thank you - I never even noticed!

WezV

That's a very nice jig.

Misterg

WezV said:

That's a very nice jig.

Ta - I've actually just used it, and (spoiler alert) it worked a treat.

Misterg

Onwards!

I used a variety of blocks and cylindrical objects as blocks to try and sand the sides flat

There were a few hollows and ripples, but these sanded out surprisingly quickly:

The patch of funky grain sanded flat but the surface was very open and 'fibrous'.

I filled this patch with superglue, and it actually came up OK.

The bindings I'm using have purfling strips attached and I had bent them roughly to shape on the hot tube previously (I did them in pairs to try and make sure that I ended up with enough left / right hand pieces).

I had treated myself to a brand new 25mm router bit to go with the binding cutting jig and spent a little time routing channels into some scrap pine to tweak the settings.

With great trepidation, and a very dry mouth, I attacked my guitar with my routing jig... 

I cut the binding channel on the back first, and it seemed to go well. The jig worked an absolute treat, and the sharp, new router bit cut cleanly.

Jeez! that was nerve-wracking!

I aimed for the bindings to be flush with the side of the body and a little bit proud of the back / top, and they seemed to come out spot-on:

While I was on a roll, I cut the binding channels in the top, too (they are the same).

On both cuts, I stopped short of the end graft on the first cut, and then adjusted the cutter depth and came back with a shallower pass over the end graft in case I could make mitered purfling strips work.

I cleaned the channels up with a chisel to leave just the purfling on the end graft...

I pared some of the purfling off the lining strip, and after quite a bit of puzzling I managed to get something that fitted reasonably well. The trick of looking at the reflection in the back of the chisel and lining it up with the direction of the next strip works surprisingly well.

(My "body is too long" - first time for everything - so will split this post)

Misterg

...Continued 

I used a different spacer on my jig to cut the purfling channels on the top. Before cutting them, I wiped some shellac around the edge of the top to try and discourage tear-out. Again, the cutting jig worked very well, but I sort of messed up by cutting almost the full depth of the top. I read in the Cumpiano / Natelson book straight afterwards that it should be a maximum of 1/16" ~1.5mm deep into the top (don't know how I missed that before). I had cut deep enough to sink most of the purfling strip which ended up being just over 2mm deep. The top still has an overlap onto the linings and seems securely stuck, so it is what it is.

 

The back bindings were glued on using Titebond and held in place with brown paper tape while it set (the bindings were lightly sanded before gluing). The tape I used is 'Sekisui 504NS Smooth Framing Tape 25mm x 50m'. I bought it from Amazon, but as far as I can tell, it's what is sold by some places as binding tape. The tape is quite tacky, but easily peels off. It has a small amount of stretch in it that helps put tension onto the glue joint. I was prepared to bind the joint with rubber strip to get a tight fit, but the tape worked really well and I didn't feel the need for anything additional - I'd recommend it.

On the top, I was intending to glue the bindings and purfling on at the same time, but after gluing the back bindings, I decided that there was enough going on without adding the purfling, so I glued and taped the top purfling into place first:

When the glue had dried (Titebond again), I cleaned up and sanded the binding channel before gluing the top bindings into place:

OMG What have I done??

Roland

BigMonka

This is epic, such a beautifully crafted instrument you're going to end up with!

Misterg

BigMonka said:

This is epic, such a beautifully crafted instrument you're going to end up with!

Thank you! I really hope so, but it could still all end up as kindling

Misterg

So how did it come out?

With the exception of a few self inflicted, faults: Very, very well!

Somehow I'd managed to catch the edge of the purfling channel on the top with the router cutter. I'm not quite sure how I managed it, but the mains lead on the router did snag on something at one point, so I presume it stems from that.

 

I hadn't trimmed the end of the treble side binding back quite carefully enough, so it left a small gap next to the purfling where the two pieces of binding join:

Most annoyingly, I had managed to dig a fingernail deep into the top when pressing the tape down:

I managed to plug the binding faults with little slivers of spruce and titebond and am pleased that after sanding back, my eye is no longer drawn to them. Hopefully they won't stand out too much under finish, but even if they do, I'm happy to live with that.

I did try to steam the nail mark out, but it didn't make much difference. I'm reluctant to try and fill it with sawdust, because I think it could end up more noticeable. I guess it will have to stay there to please the gods.

Other than that, all the glue lines were nice and tight and everything came out much better than I could have hoped.

I freely admit to not knowing  what I was doing when I ordered the binding and purfling, but I really like the way its starting to look (click for bigger pics):

It almost looks like one from a real guitar shop!

fastonebaz

I can only begin to imagine the waves of pride coursing through your body currently.   

WezV

That's a really good job.  I've done lots of complex binding, but rarely as neat as that

Misterg

@WezV ; - Thank you. I genuinely consider that high praise indeed. (But I think I've got a long way to go before I catch you up.)

@fastonebaz - Would it be weird if I confessed to just sitting and caressing it for an evening? (If so, I didn't, OK?)

I'm as surprised as anybody at how it's progressing.

fastonebaz

No I think that would be entirely normal.  I regularly caress mine for a while after a good polish.