To clarify what follows: I am about as much of a woodworker as I am a violin player. My carpentry isn't at a fine level. I'm also prone to improvisation in order to make something happen (such as the "clamps" at the end of the last post).
On the other hand, I abhor shitty workmanship. So, although the first saw cuts were rough on the V-joint, due to my lack of developed control when hand-sawing an irregular piece, that just meant I had to put in the hours of careful fiddling needed to bring the faces as close to flush as it is in my power to do. (Which is pretty darn close.) Similarly, although the screwed-on "clamps" look outrageously bad, they actually did their job. The pieces were held immobile, the joint was tight, and the combined fingerboard surface remained absolutely flat.
So, while it is true that this neck modification is within reach of anyone who's moderately handy, it's also true that success depends significantly on attention to detail. Your methods can be unorthodox, or even inadvisable (like many of mine), but if your joints aren't flush, or the neck angle isn't correctly lined up with the body, the project could come to nothing. I guess what I'm saying is that some things are extremely important to get exactly right, and some things have more forgiveness built in. I don't want to give anybody unrealistic expectations about this.
All that being said, here's how the neck looked after it came out of the clamps, and had been shaped with rasps on the back, and had the screw hole enlarged and the oak pin inserted:
Tip: You can change the diameter of your pin (or add a taper, if desired) by chucking it up in a power drill and rotating it against a file or coarse sandpaper. This allows for a very precise fitup with the hole.
As you can see, you can also fill small voids with splinters in the same way. This one only had to go in a few millimeters, but I wanted to get rid of the little hole in the back of the neck, of course! By the way, here's a photo of the rasp I used to do 90% of the work of shaping the neck:
Hopefully, it's clear from the picture that the thing has 4 cutting surfaces: coarse and medium for flat and round sides, respectively. (And yes, those are my nails; the picture is from well after I finished the instrument, and the nail polish was originally for marking the fingerboard, but obviously I couldn't resist.) Anyway, the tool was about $8. I used touch to figure out how the neck shape should go. If there was a jarring tactile transition, I knocked it down. Rinse and repeat. Then smooth off the final marks with a file that's finer, then a couple passes with sandpaper of different grits.
Speaking of sandpaper, I next flattened the heel so it was absolutely true (and absolutely at the correct angle). A good method for this is to use sandpaper attached to a table which is known to be flat--and beware, many tables are not quite.
This was coupled with cleaning out, re-flattening, and slightly widening the heel slot:
This process revealed what could have been a fatal (for this project) mistake: I had accidentally cut the heel to the wrong depth! It was too short, so the fingerboard would have touched the body, instead of floating above it. This was rectified by cutting a slice of the viola's original heel and inserting it as a spacer.
(Here, I'm holding on the viola's old fingerboard, to show the amount of "float" happening.)
I had initially taken pains to match the shape of the heel to the slot, cutting off various slices of the original cello heel to do so. Unfortunately, the addition of a spacer pushed the "V" out, creating a gap between the sides of the heel and the sides of the slot. But luckily, the gap was uniform: I could just make two shims of exacting thickness (again, sandpaper against a flat surface is your friend) and close the gap. Here is the neck, with a bit more shaping done, and all compensatory pieces glued on:
At this point, I was obsessing about the angle at which the neck joined the body. I was anxious about screwing it up, because it's all dependent on a single joint; and I was also concerned about the joint possibly failing under tension. So, after ensuring a flush fit on both the bottom and the button, and going back many times to make small adjustments, I held the joint firmly in its final position and drilled through the button into the heel. This way, I could use the screw trick again to help with the glue-up; and then, again, I could enlarge the hole to put an oak pin in it afterward, because I was still pessimistic about my joinery.
When the dry fit was as good as I could possibly make it, I disassembled the above and went to glue on the fingerboard. But that required preparing the fingerboard first, which was an entire Situation. The original cello fingerboard had been covered in thick varnish, which, first of all, the original player(s) had worn grooves through; and second of all, the varnish had begun to melt when I applied heat to remove the board from the cello in the first place.
The varnish was so thick and brittle that it was quickest to plane it off. Unfortunately, my plane iron was not sharp, and I couldn't remember how to sharpen it properly until after that whole process was done, so I marred the wood surface a fair few times. Never fear: sand out the gouges, which were shallow. But use a flat block under your sandpaper, please, and use long strokes; otherwise you'll create gradual hills and valleys on the surface.
(By the way, if anyone wants good and simple and reliable sharpening advice, watch this video: https://www.youtube.com/watch?v=20EZbxI7rrU. It refreshed my memory of what happens when you sharpen a blade, and provides comforting assurance that it doesn't have to be complicated. Also, I skipped the two middle steps--going straight from my $5 Ace double-sided sharpening stone to the leather strop--and still managed to get an edge that could shave my arm hairs, so it can be even simpler than he says.)
I also had to get the fingerboard down to thickness. The cello board was about twice as thick as the original viola board, and if I had used it unaltered, a) I would have had to use the cello nut or raise the viola nut, and b) I couldn't use the viola bridge. The original thickness would have just added too much height. So, after cutting it to its final length, I scored a line down each side of the fingerboard (so I could follow it), and sawed the thing in half. This was a huge pain. Please, if you're doing this, use a router instead. Or call your friend who has one. Or buy one from Walmart and return it afterward. (Use multiple shallow passes.) You could also use a table saw as a sort of "router" for this, set to a depth of half the thickness of the cello fingerboard, and just make many parallel cuts. But be sure to leave a "leg" on either side that you can trim off later. Anyway, hnd-sawing this hard rosewood board, in literally the most inconvenient dimension possible, was extremely laborious, and the times that I accidentally lost the line were numerous and needed to be fixed. Lord have mercy if you attempt it on an ebony board. Definitely a case for power tools.
You may be asking, at this point, why I'm still doing this project. (I was also asking this.) Part of the answer is that I am a stubborn idiot; but the other part is that I'm a metalworker, and with metal, you tend to think both additively and subtractively. Woodworking is mostly subtractive: Cut off the part you don't want. But metal does both: in some ways, welding can be additive like clay, in the sense that you're putting on more of the same essential stuff, and the joint can be functionally erased. You can weld holes shut and grind back the surface, and if you do it correctly, there will be no evidence that there was ever a hole. (Always with caveats, of course.) And there is a saying about the size of gaps between metal pieces to be joined: "If you can walk across it, you can weld it." So I take that mindset to wood. Cut off something important? Glue it back on, or glue on something that can be shaped into something like the original. Accidentally gash the wood? Fill it with sawdust and glue, and sand it back. Mistakes become a mere inconvenience rather than a fatal blow, more often than not. This is what happened with the fingerboard. After a few iterations of leveling the surface that will meet the neck (again, use sandpaper on the table!), filling my saw gashes with glue and sawdust, and knocking down any irregularities, it looked semi-presentable, as you can see:
You can still see a half dozen areas of damage. I could have gone further, but at that point, I decided that there was sufficient surface area flush with the neck to hold the fingerboard in place without it popping off. And the other side looked good.
I had retrieved the real clamps from my ancestral home at that point, so it was time to attach the fingerboard to the neck:
(The beer was necessary.) You'll note that I'm using hide glue for this. Chemically treated Tite Bond-brand hide glue, which is liquid without being heated first; but hide glue nonetheless, which is rather weak. This is because I may end up wanting to take off this fingerboard at some point, and I do not wish to repeat the experience I had with the cello.
Yes, that's a zip tie on the end. Why should it be a surprise at this point? Also, I left the fingerboard's initial width untrimmed, so I could just plane it down to the sides of the neck once it was on there, and pretend like my alignment was very accurate. Looks pretty slick:
After that, it was a simple matter of gluing in the heel joint. Depicted below is my final dry-fit with the screw as guide. After this, I took it apart, glued it up with hide glue, put the screw back in, and put on a single clamp, which pressed the floating end of the fingerboard downward toward the body (and thus pressed the heel into the bottom of the slot). Such clamping might have pulled the back of the heel away from the button, but the screw prevented that.
After it was all dry, I put a pin where the screw had been, and then carved down the button to match the heel. (Andrew Carruthers, from the article I linked in the first post, says that trimming the button like this is "very bad practice." Bruh, everything about this project is very bad practice, yet here we are.)
Because I used hide glue for the neck joint as well, I could conceivably pop it off again later if it needs to be re-set or replaced. The pin would need to be drilled out first, but that's OK. Hopefully any future luthier will see the pin for what it is, and won't think it's some kind of ill-advised ornamental inlay.
I took a closeup so you could see how much wood filler was in the button in the first place. I don't know what they did there, or how much more filler is in the actual back (or top, or ribs) of this instrument, but it's again comforting to consider that I am not ruining that which has not already been ruined a little.
Now, to everyone's surprise, the instrument is in a state in which it can be strung up. I was elated, at this point, to discover that it plays just fine, and sounds just like a beefier viola.
This post is already running a bit long, so I'll save the adventures with the fine tuners, the bridge, the string materials, and varnishing the neck for the final post. (Oh, and addressing that separation between the back and the rib on the lower bout!)
See ya next time, and remember: No gods, no masters.