Of all the carving operations associated with stringed musical instruments carving the scroll of violin family instruments seems to be one of the most difficult to grasp. As a matter of transformational geometry it is certainly more complex than say, carving a neck shaft. But just as in the carving of a neck shaft the process of transforming a block of wood into a pegbox and scroll is one of successive approximation. The first steps only crudely transform the block, but successive steps refine the shape more and more until the result is the desired size and shape.
Last updated: Tuesday, May 08, 2012
The very first thing that needs to be done here is to obtain very complete templates for the pegbox and scroll you wish to make. Since tradition is so strong in the violin family, most folks will start with patterns taken from existing instruments. You can either take these directly from instruments or use the patterns included with any of the violin building books or plans available. The series of posters put out by the magazine The Strad have great drawings on the backs that can be used to good effect. If you want to derive your own scroll pattern while staying within the bounds of tradition, take a look at the drawing of scroll and pegbox proportions that appear in Ed. Heron – Allen's book Violin – Making As it was and is. There is also a wonderful article by Robert J. Spear in American Lutherie #95 on the subject of drawing the violin scroll. While I'm suggesting reading material, I would be remiss if I didn't recommend the excellent article on scroll carving by Guy Rabut that appeared in American Lutherie #52. And be sure to see the nice page on carving the violin scroll done by Derek Roberts.
In the following paragraphs I'm detailing the construction of a pegbox and scroll for an electric upright bass (EUB). Its large size makes it easy to photograph and for the most part everything needed to make a bass scroll is needed for smaller scrolls as well. One caveat though. This pegbox and scroll assembly does not fit the traditional proportions of such an assembly. Although the width of the pegbox is constrained by a number of factors, the overall length of this assembly was shortened to aesthetically “fit” the EUB. So this scroll is a little chubby-looking. This doesn't matter at all with respect to the techniques involved with carving, but you should be aware that, proportionally speaking, you are not looking at a typical scroll here.
Another note. For most bass instruments, I build the pegbox and scroll separately from the neck. It is a lot easier to handle and it saves a lot of wasted wood that way. Also, the scroll/pegbox assembly can be made from a single block of wood, but here I am making it from two pieces, one for each half when viewed from the front. As with all wood carving, the process of making a scroll is one of successive approximation. The early steps take away large hunks of waste wood and rough out the shape, while subsequent steps take smaller cuts and refine the shape.
The first step is to transfer the horizontal profile of the assembly onto the two blanks. Next, the holes for the tuning machines are drilled.
This is done before the pegbox is excavated to avoid blowing out the bottoms of the holes as the bit enters the pegbox. Unlike violins, basses don't use pegs, so the holes don't go clear through the pegbox to the other side. Note the wedge under the block, which angles the holes so that they will end up perpendicular to the (angled) sides of the finished pegbox, something you need to do if you are using tuning machines, but something you wouldn't do if using pegs. After the machine holes are drilled most of the waste wood inside the pegbox is excavated using a template and the router. This excavation can only be done this way if the pegbox/scroll is made in two halves. If a single blank is used then most of the waste has to be drilled out of the pegbox from the top. After the pegbox is roughly excavated as described, the two halves are aligned and glued together. Then the horizontal profile of the pegbox/scroll assembly is cut out on the bandsaw and sanded smooth on the spindle sander. You can't get into the place where the scroll meets the pegbox with the sanding drum of the spindle sander. Cleaning up that part of the assembly is put off for a while. There will be less wood there later.
You can see that the pegbox excavation is not complete – the router left the cavity rectangular, but ultimately it will be trapezoidal. That work is done by hand with carving tools. First the vertical profile of the pegbox is transferred to the blank, then the carving begins.
I do this with chisels, knives, and gouges. There is not too much wood to take out so the work goes quickly. The scroll pictured is made of mahogany, which is particularly easy to work, so most of the carving involves pushing the carving tools by hand. If the scroll is made of maple then some mallet work is required at this stage. After the walls of the pegbox are cut, the floor is cleaned up.
The horizontal profile of the scroll itself is transferred onto the blank at this time. You can see that I've cut out the spiral of the scroll in the template using a hobby knife. The traditional method of doing this is to simply prick holes right through the paper template into the wood, but my old eyes have a tough time seeing all the pin pricks and, since I'm prone to making mistakes anyway, I'd rather work to a nice solid line.
The walls of a bass pegbox have to be a minimum of 9/16” thick if standard electric bass machines will be used, as in the instrument shown. If the excavation of the pegbox ended up making the box a little wider than planned, then the lines representing the outsides of the pegbox would be redrawn now. When I'm satisfied with the vertical profile of the outside of the pegbox it is time to cut out the pegbox on the bandsaw. You can see a notch in the front face of the pegbox. This is to allow access to the trussrod adjusting nut from the pegbox. Again, I'm building for an EUB here, and this one has a trussrod.
I don't cut into the scroll at this point, just the pegbox. When this step is completed, the assembly will look like this:
The vertical profile of the first turn of the scroll will be marked next. The steps I am describing here are to do this on a more or less ad hoc basis. If one is attempting to copy an existing scroll then a paper template of the vertical profile of the first turn of the scroll is used to mark the blank.
This would be a good time to talk about how the side faces of the scroll will look when the scroll is done. If you take an instrument with a scroll and orient it sideways so the axis of the scroll is pointing up and down and then look at it from the back, the surface of the side of the scroll (now facing up) can be seen as a sort of ramp. The ramp moves down along the pegbox, and continues to move down as you go around the first turn of the scroll. The ramp starts to move upwards as you approach the front of the pegbox, and it continues ramping upward as you go around the scroll again to the button. As you approach the button the surface of the side of the scroll tilts toward the outside, so that only the outside edge of the side actually meets the button. First timers will want to have a carved scroll on hand when attempting their first scroll carving. This will serve as an invaluable reference.
By the way, the reason the vertical profiles of the scroll sides are marked one turn at a time instead of marking them all at once is because, once you cut out the waste for the first turn you will have cut off your marking for the next turns. So the procedure is to mark the profile for each turn of the scroll, then cut out the waste for that turn. Cutting out the waste leaves the surface in a series of steps instead of a ramp, but these will eventually be planed to a smooth ramp.
The first step to mark the vertical profile of the first turn of an ad hoc scroll is to draw a horizontal line perpendicular to the scroll's center line at between approximately 9 o'clock and 12 o'clock, when the scroll is viewed from the side. This will represent the narrowest point of the first turn of the scroll – the first turn of the scroll narrows as it exits the back of the pegbox and continues to narrow until it reaches this point, then it starts to widen again. When it reaches the top of the pegbox it is generally a little wider than the top of the pegbox. If this line is very short the finished scroll will look kind of pinched in. If it is too wide the scroll will look bulky. A reasonable approximation is to make it about a third of the total width of the finished scroll.
This photo shows the approximate place to draw the line at 10 o'clock:
The next step is to draw a line from the edge of the back of the scroll around the back of the scroll to one end of the line drawn in the previous step. This is done on both sides of the scroll. From the back the lines look like this:
Now the same thing is done from the front, but this time the lines should begin a little bit outboard of the outside top edge of the pegbox. From the front the lines look like this:
I'm using a flexible ruler or spline to draw the lines.
Here's how the lines look from the “10 o'clock” position:
The lines meet at a sharp angle but in the finished scroll the curves will be nice and smooth. The connection between the line is smoothed out at this point. I just eyeball it when making an ad hoc scroll.
After the vertical profile of the first turn of the scroll is established the waste wood between the first turn and the second turn is chopped out. The two ways I typically do this are with a saw or a small router. The router is quicker and messier but only works for a bass scroll because a smaller scroll just doesn't have enough surface to rest the router on.
But the saw method cannot be ignored completely because that is the method that will be used to hog out the waste for the inner turns later. The basic idea in both cases it to quickly hog out as much material as possible, while keeping the sides of the scroll perpendicular to the shoulders as I go. Because the sides go in and then out on the first turn, care must be taken to not take off too much wood at this step. Once the first turn is hogged off it looks like this:
You can see how the side faces of the first turn have steps in them from the hogging process. The next step will be to establish a smooth blended face on each side of the first turn of the scroll, while at the same time keeping the shoulders of the second turn perpendicular to the sides. I'll use chisels and rasps to do this for the mahogany scroll. If the scroll was made of plain maple or poplar I'd probably also use a small plane and would probably need a lot more mallet work with the chisels. Figured maple would get the same treatment but also much more care to prevent tear out. Whenever I do tear out a big chunk unintentionally I simply glue it back in with cyanoacrylate and keep going. Note that in the finished scroll the sides will be undercut, that is, slightly hollowed out. At this point though everything should be kept square.
One of the issues with carving a scroll by hand is keeping things even and symmetrical. After the face on one side is smoothed out as described above, measurements are taken from the centerline to the edge of that face at various points. The line representing that edge on the other side of the scroll is redrawn so that the two faces will be symmetrical. Then the uncarved face is carved. Here's the first turn roughly carved:
When all goes well, I can complete a scroll without a carving mishap. Every now and again, though ...
Now that the first turn is carved, the vertical profile of the second turn is marked on the shoulders. For an ad hoc scroll like this one I just connect the end of the first turn with a point half way between the face of the first turn and the uncarved end where the button will be.
The waste wood is removed in steps as per the first turn. This time I'm using a razor saw.
Now the face and shoulders of the second turn are carved. When this is done on one side the line for the other side is reworked to straighten things up and then that side is sawed and carved. A final straightening up may be in order after all faces are rough carved. Then the button is carved with knives and gouges. After all the rough carving is done it is time to clean up the space between the pegbox and the outside of the first turn. This is done with small files and then with sandpaper.
Then all of the carved surfaces are straightened up with coarse grit sandpaper and flat sanding blocks. The inside of the peg box, the top of the pegbox, and the sides and shoulders of the peg box and scroll are surfaced. Since the side faces of the scroll will eventually be undercut it is not necessary to completely smooth away all tool marks there during this step. Sanding on these surfaces is done with complete disregard for grain direction too, for the same reason.
After the sides and shoulders are squared up and the curves made smooth the sides of the scroll and the back of the pegbox and the first turn is marked for undercutting. The sides are marked about 0.125” from the edge for the bass scroll, and the back is marked in a similar fashion.
The bass pegbox and scroll is wider than the neck, so the corners between the sides and the surface that will be glued to the neck are rounded over.
I start to undercut the sides of the scroll first. Since the tuning machines need to be mounted on a flat surface the sides of the pegbox are not undercut. Some folks do undercut here for instruments that use tuning pegs. If the pegbox sides are to be flat the side surfaces have to transition smoothly from flat to undercut at the scroll. Undercutting the sides is done quickly, using medium sweep gouges. As the sides get narrower as the scroll winds in, I need a number of sizes of gouges to do this. For this mahogany bass scroll the palm tools shown work well. If harder wood is involved then some mallet work is needed in this step.
After the sides of the scroll are undercut the two channels up the back of the pegbox and around the first turn of the scroll are undercut. Since the channels are pretty wide on the bass scroll and pretty deep, this is done with a combination of mallet tools and the palm tools. The work is clamped down well for the mallet work. The channels start in the back ...
... and then work their way around to the front. It takes some fussy work near the end of the channels as the scroll rolls back into itself. In the picture you can see a piece of plastic which is tucked in between the scroll and the pegbox. This keeps me from dinging up the top of the pegbox while I'm carving the front of the scroll.
Once the carving is complete the entire scroll and pegbox is cleaned up using sandpaper and scrapers. The broad flat surfaces on the sides of the pegbox of the bass scroll are ideally suited for sanding with a block, as are the insides of the pegbox. But scrapers are used on the rest of the areas as the sandpaper tends to round over the edges and mush up the crisp lines of the carving. This is a matter of tradition, as the finish of such scrolls was established in the days before sandpaper was invented. Folks that carve scrolls generally use an assortment of scrapers to do this. I start out in the undercut channels on the back of the pegbox, working in the centers of the channels first and then moving toward the edges so that the clean edges can be retained (and straightened up as need be).
After the channels are completely scraped out, the undercut areas on the side faces of the scroll are scraped. Then the flat surfaces on the shoulders of the scroll are scraped, cleaning up the inside edges between the shoulders and the sides in the process. The flat surfaces along the borders of the undercut areas are scraped next. The last scraping step is to chamfer the sharp edges on the entire scroll and pegbox assembly. The entire piece is rubbed often with a rag to remove dust and get a good view of the surface. I end up missing some areas that need more attention, so I generally rub paint thinner on the piece to highlight the areas that will need more work.
Those areas are either reworked or, if there are a number of them, they are marked before the thinner evaporates. Once all tool marks and sanding scratches are scraped out and the surfaces are smooth and flowing the scroll and pegbox are done.