Posts Tagged ‘Japanese pull-saw’

Cello Neck-set

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Here’s how I set the neck of a Cello

I’m quite sure it is virtually identical to how other makers do it, with one possible exception: I set the neck while the corpus is still on the mold, with only the front plate installed.

Cello corpus on the mold; front plate installed;

Lay out the mortise outline.

I lay out the center of the neck block, and perform the remaining layout from that centerline. The heel is to be 30mm wide, and the front of the neck where it joins the corpus is 42mm wide. So I mark 15mm to each side of the centerline at the heel, and 21mm to each side at the front plate. Double-check everything. It is a real pain trying to put wood back.

I check my measurements, and mark the location on each side of the neck where the front plat should sit when all is complete– 280mm from the top of the fingerboard, and 20mm down from the top of the neck at the front.

Then begin cutting.

I have five measurements in mind, which I check constantly:

  1. I want the neck centered, obviously, but in terms of simple location, I accomplished that by careful layout– I want it centered, in that the fingerboard will be centered on the corpus, and the centerline of the scroll will be in line with the centerline of the front plate, as well.
  2. I want the neck straight, in the sense that it is not rolled to one side or the other. I can check this by sighting across the “ears” of the scroll at the edge of the front plate. If they seem parallel, I am satisfied.
  3. I want the neck the proper length. That 280mm mark I put on each side of the neck will let me know when I am getting close.
  4. I want the front of the neck the right height off the front plate. That was the 20mm mark I put on each side of the neck.
  5. Finally, I want the neck angle to be such that the bridge will be an appropriate height. I aimed for 65mm at the end of the bridge, so as to arrive at an 82mm projection at the bridge– the bridge, then would be roughly 90mm tall at center. There is some flexibility on this one, but not a great deal. In reality, all five of these measurements simply have to be within tolerance, or the instrument will not work right.

So, with all of that in mind, I measure from the 280mm mark to the end of the neck, to see aproximately how deep the neck mortise must be at the front, then use a Japanese pull-saw to slice along my layout lines to nearly that depth. I stay inside all my layout lines, as I want to leave a little room for adjustment.

 

Cello neck-set 1 of 6

I begin by removing the section of front plate affected by the neck mortise, then use a chisel to remove the waste wood from the mortise itself.

The blue lines you can see in the above photo remain from my initial layout when I bent the ribs. I wanted to make sure they were long enough. (It was close!)

Cello neck-set 2 of 6

I try to get the mortise nearly right on the first try, but deliberately leave some room for adjustment.

Cello neck-set 3 of 6

You can tell from the location of my layout marks that I still am far from done– but the neck fits fairly well, and I will be removing paper-thin shavings from here on, and checking every step of the way.

Cello neck-set 4 of 6

Now you can see that the layout lines are very close to what I wanted. In fact, I had deliberately marked my height at 21 mm, to give room for adjustment… and it is at 20 mm now, which is fine. The 280 mm mark is dead on target.

Notice that the heel is overhanging the back of the block by nearly 5 mm. That is fine– I will remove that excess wood when I flatten the back of the garland, and the back plate will be the last major component installed.

Cello neck-set 5 of 6

Here is a closer look– the length from the top of the fingerboard to the edge of the front plate is pretty critical. a good player will notice any variation. the overstand (height above the front plate) is less critical.

Cello neck-set 6 of 6

I checked and double- and triple-checked until everything was perfect, then slathered the hot hide-glue into the mortise and onto the neck, then rammed the neck home and clamped it tightly. I checked once more with the clamps in place, to see that the measurements were still OK. (Thankfully, they were!) Cleaned up with hot water and a brush. Now it just has to dry.

That clamping block in the photo above was just a scrap of wood– I cut it to the correct angle, then hollowed out a curved opening to fit the cello neck-heel. I glued a pad of 1/8″ cork into the cup, and it works very well.

And that is pretty much all I got done today. Cooked a roast… fed the cat, brought in the newspaper…that’s about it. Pretty tired.

Later tonight, if I still feel like it, I will remove the mold, and begin the final cleanup of the interior of the corpus. On the home stretch, now… well,  almost! 🙂

(Edit: I did go back and remove the mold, but that was all for that night. 🙂 )

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How I carve a Scroll

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Cello Scroll Carving Made Simple 🙂

There is nothing special about the way I carve scrolls. As far as I know, this is how everyone else does it, too, more or less. I am only sharing how I do it.

Start by tracing and sawing out the profile of the whole neck.

I don’t have a photo of the scroll as a simple profile, but I begin with the billet (About 6″ x 3″ x 20″), and trace my template onto it, then use a bandsaw to cut the shape of the profile. I use a oscillating spindle sander to remove the saw marks, and perfect the profile right to the line. While the profiled block is still “square”–that is, while the sides are still parallel, I lay out the peg hole locations and use a drill press to make 1/8″ diameter pilot holes where each peg will be. I drill all the way through, so that the holes are clearly marked, and are perpendicular to the center plane of the neck.

Next cut out the pegbox and at least a few inches of the neck

I hollow out the pegbox before carving the scroll proper. Some people use a drill to get started. I have done it this way, but it seems a little risky, unless you put some sort of limiter on the drill, to avoid going too deep– and even then it is easy to go out of bounds. I use a narrow chisel to remove most of the rough wood, then a wider chisel to smooth the inside cheeks of the pegbox. I also saw off the excess wood on the outside of the pegbox, and plane those faces flat.

Then draw the shape of the scroll itself.

Usually we use a template for this, as well. Some people plot out each scroll with a straight-edge and compass. I have neither the time nor the inclination. In this case, my templates came from a poster of the 1712  “Davidov” Stradivarius cello, now being played by Yo Yo Ma. Some information was lacking, and I filled that in from Henry Strobel’s book on cello making.

And begin cutting:

Once the scroll is drawn out, I clamp the neck to my workbench and, using a Japanese-style pull-saw, I begin cutting slots nearly to the layout lines of the volute. I rotate my position a few degrees, and make another cut. I have to be careful to avoid cutting too deeply, but this method allows me to chip away the waste wood rapidly, and the scroll begins looking like a scroll rather quickly.

Beginning the scroll, proper.

Pegbox is complete, volute partially carved. The cut lines are visible on the portion of the volute that has already been carved. Now we will carve the scroll, proper.

Cutting more kerfs to remove wood.

Care must be taken to avoid drifting across the line into the turns of the volute.

Cutting a series of kerfs for wood removal in carving a scroll.

You can see the direction this is going…I will continue to slice down nearly to the line, rotating a little each time, until I have gone all the way around.

Using a gouge to outline the eye of the scroll.

Once the kerfs are all in place, and to the correct depths, I use a gouge to outline the eye of the scroll, so as not to damage it with the saw.

Kerfs in place, and eye of scroll deeply incised. Carving can begin.

All the kerfs are complete, and the eye is deeply incised with the gouge–I am ready to start carving.

Use a flat chisel to remove the waste wood, and the scroll begins to emerge.

I use a flat chisel to remove the waste wood, and the scroll begins to emerge.

Once the waste wood is completely gone the

Once the waste wood is completely gone the “undercut” carving can begin.

Bi-lateral symmetry

I try to make sure the two sides match symmetrically, before beginning undercut. I do the outside fluting last, to avoid damaging it while carving other parts of the scroll.

Bass side of cello scroll, nearly complete.

Here is the bass side of the scroll, nearly complete.

Treble side of cello scroll, nearly complete.

And, here is the treble side.

Cello neck and scroll, nearly complete.

The neck and scroll are nearly complete. I will continue to fine-tune and scrape the scroll, perfecting it as best I can, right up to the day I begin varnishing.

Fingerboard installed on Cello neck, with hide glue and clamps.

I have prepared the fingerboard, and now I have installed it, using hot hide glue and clamps.

So– that was entirely enough for today. Tomorrow I will continue to refine the scroll and neck, and try to get the neck set. If I succeed, then I can remove the mold and install the back plate.

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