Posts Tagged ‘graduation’
Beginning Graduation (inside carving)
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Beginning Graduation (inside carving)
How Thick?
This becomes another critical issue: How thick should the plate be at any given point? I will try to follow the poster to some degree, but it was only correct for that particular instrument, with that particular set of plates. The wood I have may not be anywhere close to the same stiffness or density, so I have to get into some sort of “ball-park” range, and then start making decisions based on this wood that I am carving. How it feels, how it flexes, how it sounds when I tap on it, all make a difference in my mind, though I am aware that there are some standard thicknesses to which many makers adhere.
Others measure the vibrations of the nearly completed plates using a frequency-generator, and try for certain frequencies to make a certain set of patterns (called eigenmode frequencies, and nodal patterns, or Chladni patterns). I have tried this and couldn’t get it to work for me. Then, one day at a workshop, one maker was haranguing me that I wasn’t graduating my plate correctly, and took me out to the plate-shaker thing, and demonstrated to his satisfaction that I had it “all wrong”. I had simply followed some graduation thickness numbers given me by a master maker (who does not want me mentioning his name), so I could not tell him that. I was feeling pretty glum about the whole exchange, when he looked up and saw another maker coming in, who he considered to be an expert at testing plates. He said “Ask him! He’ll tell you!”
So, the other fellow obligingly came over and began setting up the plate-shaker, while the first guy stalked off.
I noticed that the second guy did not set it up at ALL like the first guy had done, but I kept my mouth shut. He ran through the frequencies and numbers, and finally said, “It’s perfect! Don’t do another thing to it! Install the plate!”
So, I walked back into the work area, not intending to say a word, but the first fellow was waiting for me: “Well?! What did he say??” I repeated, verbatim, the second fellow’s verdict. The first guy said “What??!! How come I got the numbers I did??” I replied, “I couldn’t tell you! I don’t know how to run that machine!” No more interference that week… 🙂
So…the point is, there are a variety of ways to achieve the goal of good plate graduation. That experience convinced me that even just following a set of established thickness values can work just fine. And, ultimately, that is probably about what I will do, on this violin.
Moving Wood
I began with a gouge, trying to get within a few millimeters of the right center thickness.
Beginning inside carving with a gouge.
Then I switched over to a toothed plane, which I find more comfortable to use. The handle on it is a modification I added to shift the pressure to the heel of my hand instead of my thumb and forefinger.
Toothed plane progress.
The normal orientation of the screw in the Ibex plane (left) has been reversed to hold the wooden handle as well as the blade.
Repairs
But then I heard a cracking sound: Not a good thing to hear when you are working on a violin. I looked the plate over and could find nothing amiss, so I went back to moving wood. Heard it again, louder. (Sigh…)
It turned out my work-cradle had broken! (What a relief!) Well, I made it 15 years ago, and it has served well, so I took the time to glue it and insert three dowels, diagonally, through the break, to hold the joint against further failure.
Repair of broken work cradle.
Work cradle construction: a heavy pine plank with a cutout to support the margin of the plate. Thin plywood surrounds the plate-edge.
Back to work:
I am aiming for about 4 millimeters in the middle, and all over, which I will refine later to the specific measurements I want. In the photo, below, reading the dial on the caliper, you can see I am nowhere close. But…I’m tired, and I’m going to call it a night. By the way, in case anyone was wondering, those jagged-looking black pencil lines around the lower corners are outlining an area that was pretty close to the right thickness already: I don’t want to touch them until I am on the home-stretch where graduation is concerned. It is VERY easy to get too enthusiastic and carve too deeply in such an area, and ruin the plate.
Long way to go!
So, next time, I hope to have the graduation complete, so I can cut out the f-holes and install the bass-bar.
Thanks for looking.
Progress on a 14-inch Viola
Continuing on the 14-inch Viola
Arching and Graduation
The outside arching for the front plate is essentially complete, though there will be a lot of scraping, later on. I began the graduation (inside arching) of the front plate about the same time as I took off and “sprinted for the finish line” with the “Plowden” Guarneri-model violin (see recent posts), but all I accomplished was that the center of the plate is about the right thickness– everywhere else it was still way too thick.
So! Back to work! You can see (below) that the f-holes have been laid out and deeply incised, which allowed me to accomplish the last stage of the front arching (explained in an earlier post.) Now I need to carefully carve away the interior, until all the plate is the thickness I want it to be…which varies by region, all over the plate. I have to be very careful to check certain areas with a caliper before I begin to carve, or I may easily go too far and make the plate too thin. (Voice of sad experience….) The area around the lower ends of the f-holes are very likely victims of this error, so I try to check regularly, and avoid carving away too much in those areas, especially.
The outer arching of the small viola is complete, not counting the purfling channel.
Side view of the small viola’s arching, before purfling and edgework is done.
Inside arching of the small viola. The Graduation is complete. Next, I need to cut out the f-holes, and add the bass-bar. I do realize the corners are too long…I will trim them later.
Coffee Stain
One thing I decided on this instrument was that I should begin the coffee staining very early, so that, if there is any distortion, due to the wetting of the wood, I can correct it before the plates go on the garland. In this photo, it is hard to see how much the grain is raised, but, those wide summer grains of the Sitka Spruce are all swelled up like corduroy!
Accentuated grain lines, due to coffee stain.
I will let it dry, and then gently scrape it smooth again. The issue, here, is that the summer grain swells more than the winter reeds, but when we scrape the wood, the summer reeds compress, while the winter reeds resist the blade and are cut away. The result is that the summer reeds are already raised, even before I wet it down and deliberately raise the grain, before leveling it again.
Things remaining:
When the plate is nearly perfect all over, I will finish cutting out the f-holes, and finish their edges as well as I can. I nearly always see something later that I have missed, so I just accept the fact that I will be making corrections right up until the time I begin varnishing. The same thing applies to the scroll. It will never be “perfect”, and I accept that.
I will lay out and fit the bass-bar, trying for an air-tight fit between the bass bar and the inside of the front plate. I install it using hot hide glue and clamps, but will trim it to the proper shape after the glue is dry.
After the bass-bar is fully completed, I round the inner edges of the front plate, so that it is ready to install on the garland.
Post Script:
All of the above was accomplished three weeks ago, before we left on vacation, so it should have been published then, too…but I kept thinking I would get a little more done before we left, so it simply did not happen.
We are back, and progress is once again happening, so I will post more in a day or two.
Thanks for looking.
Current “State of the Fiddles” report.
Slow Progress, But Moving Along!
Scroll-carving
I spent most of Saturday working on carving the viola scroll. I am not as fast as a lot of luthiers seem to be. It takes me more than eight hours to carve a scroll, and I can’t go at it for eight hours straight, anymore, anyway. So, between the heat and my other responsibilities, this is pretty much all I got done. It is still not complete, of course, but it is looking closer to complete, and it feels encouraging, to look at it.
This is a Big Leaf Maple scroll and back, on top of a Sitka Spruce top plate. It is interesting to carve domestic maple in close proximity to European maple. They are not the same at all. The big leaf maple is much softer, and feels almost fuzzy, under the scraper. Much lighter-weight, too, and has a different ring, when I tap it. European seemsto be superior for violins, though domestic maples seem to work fime for larger instruments (or possibly it is the lower tones involved.) This instrument will be a good “experiment” in that regard. If this instrument is very good, then the lower tone is the issue– if it is questionable, I may repeat the experiment immediately with European Maple and see if that corrects it. If it does, then the size of the instrument may be what is the problem.
But I suspect it will be a very good viola. I have made other very small (14-7/8″ on the body) violas using the same woods, before, and they were very good. This will be the smallest I have made, using domestic woods.
Partially completed scroll for the 14″ viola
Planing and flattening the plates
Actually, come to think of it, I did do a little more– I went and used my son’s tools and planed the two violin plates to appropriate thicknesses to start working them. I was shooting for about 17mm thick, to begin with, so that my finished arching will be close to that thickness, after everything else has been carved away. Then I laid-out the shapes of the plates by tracing them from the completed garland, and cut them out at home. So, here is what the whole pile looks like today. Last week, some of the plates were still square and flat, and very thick…this week they are all the correct thicknesses, and one scroll is nearing completion.
The lines on the right-hand maple plate (the viola back) are sketching in where the carving will happen on the inside of the plate: I will carve the outside first, to get the exact arching I have planned, then carve the inside to a similar shape, to get the exact thisknesses I hope to achieve (called “graduations” because the thickness is different in different areas, and changes gradually from area to area.) Both the arching and the graduations are critical to the final resulting sound. In my opinion, the arching is probably more important, but I can’t prove it.
I do know that when I accidentally arched some of my early violins the way (I later was taught) a viola is supposed to be arched, those violins sounded like violas, in spite of everything else about them being “violin.” It was very perplexing to me, at the time, as my ear was not well-enough trained to hear the difference, and all I knew is that it was a violin! And these crazy players kept telling me it sounded like a viola! They were right! The arching was the issue that decided the character of the sound. Good learning experience.
Current State of the Fiddles
The wood on the left is European maple and spruce I bought from International Violin Co., in Baltimore, MD. I have used their wood before, and it has worked well. Both have linings and blocks made of weeping willow.
As you can see, both instruments have one-piece backs, and two-piece, book-matched fronts (sometimes referred to as tops, or bellies). In both cases the ribs and necks/scrolls are of wood matching the back plate.
I will keep you all posted.
Thanks for looking.
5 String Progress Report #11; Back Plate Complete
Five String Progress #11: Back Plate completed and installed.
Inside arching
The inside arching took a lot of time and energy, but it is just part of the job. Once it begins to get closer to completion it is a lot more encouraging, but initially, it is just a lot of work.
Beginning the inside arching of the back plate.
Bit by bit, however, the project begins to take shape:
Back inside arching in progress. I made those wooden handles for my Ibex planes so I would not blister my fingers using the planes.
Graduation:
Here, you can see the curvature of the plate, but you can also see why I have to stop using the planes, relatively early, and revert to scrapers: the curly wood tears out badly under the plane.
I also have to measure the thickness over and over, using a graduation caliper, so as not to cut too deeply. This process is called “graduation”, I suppose, because the thicknesses have to gradually change from area to area. They are not entirely symmetrical, but there is a general plan and some practical limitations.
Inside graduations in progress.
Scraping:
Now we work with scrapers:
Scrapers cut very smoothly, and usually without any tear-out. You can make the scrapers any shape you want, but you have to keep them sharp.
Scraping can be hard on the hands: some people make handles for them. I haven’t done that yet. My thumbs get pretty tired, though.
Final inside preparation for gluing:
I almost forgot to take pictures! At this point the plate is complete, except for purfling. In the past, I have always installed the purfling before attaching the plates to the corpus, but on this instrument I decided to try purfling after plate installation. I think I like it. I have better control of my edge over-hang in terms of both size and shape.
So: the inside edgework has been done, the label is installed, and the plate is ready to be glued in place.
Back plate ready to install.
Plate installation:
What I do, nowadays, is to carefully dry-fit the plate to the garland so that it is exactly the way I want it, clamping securely over all the blocks (about eight clamps in all). Then I remove a couple of clamps at a time and slip hot hide glue into the joint, wipe it down with a rag and hot water, and re-clamp that area, adding as many clamps as will fit. I work my way all the way around the plate, and never have to hurry, or suffer any fear that something will get out of alignment while I am working.
For the first four of five instruments I made, I would apply glue all the way around the garland then engage in a panicky race to get the plate aligned and all the clamps in place before the glue gelled. Not good. Usually, about that time, the phone would ring, too… (sigh…).
This way is very peaceful, by comparison, but I have learned to be less compulsive about answering the phone while gluing, too.
And here is the completed corpus, with the back plate glued in place and secured with spool clamps:
Back plate secured with hide glue and spool clamps.
Once the glue is dry, I will be ready to begin purfling the back plate.
Thanks for looking.
5-String Progress #9: Back Plate
Five String Fiddle Progress: Back Plate
Flattening the back of the garland
After the glue was completely dry, I removed all the clamps from the linings and cleaned up the interior: that is to say, I tapered the back linings, so that they faired smoothly into the ribs, and I shaved and scraped the blocks to their final shape.
Then I rubbed the back surface of the garland (rib and block structure) on a “sanding-board” to level the back of the garland, and to ensure that the back of the neck heel was completely level with the back of the garland. That way, I can fit the back plate absolutely flat against the garland, and trace the shape.
I didn’t take a picture of this procedure, this time. Here are some taken when I was building a cello:
Sanding board with cello garland
Flattening a cello garland on a sanding board.
I make pencil-marks on the edges of the linings, ribs and blocks, all around, and scrub until the marks disappear. When all the marks are gone, the garland is flat. It gets pretty vigorous and physical, but it is quite effective.
Here is the flattened garland, ready to trace the back plate:
Flattened garland. Notice that the neck heel is dead-flat level with the back of the garland.
As you can see, the blocks are quite smooth, now, and the linings taper gently into the ribs. After this point, there will be no more changes to the interior of the corpus, except as it directly affects the back plate.
Tracing the plate
I clamped the plate to the corpus, carefully centering the glue-seam of the back plate on the centerline of the neck and the end block.
Garland centered on the back plate
Garland clamped to the plate.
Then I traced around the garland using a ball-point pen and a flat washer whose flange is exactly 2.5 mm wide, so that my line will be 3 mm from the ribs, all around. I watch carefully to make sure the washer stays flat on the plate…they have a tendency to flip up and follow the pen. I work along the perimeter, giving several strokes to every part, so that the line will be visible against the dark wood. Notice that this procedure makes “round” corners. I will modify them before cutting them out, so that they are the correct shape.
Tracing the shape of the plate, using a washer and a pen. (Yep, that is a Gunderson pen!)
And, there is the plate, almost ready to be cut out:
Traced plate, almost ready for cutting out.
One thing I do, that I forgot to photograph, is that I re-shape the corners. I use a straight-edge to connect a line from the end of the rounded corner where the pen circumscribed the corner of the rib to the center glue line at the location where the purfling will cross the far end of the plate. (Or, you can just use a 30/60/90 triangle to lay out a 30-degree angle off the center glue line on the end of each corner. But I do it with the straight-edge.) Then I continue the curves of the inner bouts to connect with the straight lines I just scribed in, and the corners are complete. I use a sharp scraper to remove any ink lines that are not part of the perimeter outline, and then I really am ready to cut out the plate.
Cutting out the plate
I use a band-saw to cut within a millimeter of the line, and then use an oscillating spindle sander to perfect the edge, right up to the lines. These and my drill press are pretty much the only power tools I use, though I have occasionally used an angle-grinder with a coarse sanding disc to remove rough excess wood, on larger instruments.
I run my fingers around the edges looking for lumps, and work those out as well, using a file as needed. Here is the completed plate blank:
Plate cut out and ready for arching.
At this point I also sketch in the interior graduation plan–just the outline of the inside boundaries of the plate, so that I know where I am going to carve. There is no reason it has to be done at this point, but it helps me remember which side was outside and which inside…and that really does matter, as the plates are vitually never exactly bilaterally symmetrical. If I forgot and arched the wrong side, the completed plate would never fit the garland (ask me how I know…).
Interior Graduation boundaries sketched on correct side.
You can see that there are numerous bark inclusions in the wood, which I will fill with matching wood…but I will wait until the arching is complete before I attempt to fill the holes, so that I do not plane away my plugs. It is unsusual to use wood with holes in it like this, but it is also unusual to use anything other than maple for a violin back. Five-string bluegrass fiddles are not burdened by the same 300+ years of tradition as violins, though, so exotic woods can be used. This wood has amazing flame and figure in it, and the plugged holes will not detract from the beauty of the wood.
Before I begin arching, I establish the edge-thickness all the way around, using a “wheel-style marking gauge“, set to 4 mm. It has a tiny sharp wheel that does the marking, and it makes very cleanly scribed lines.
Edge thickness marked on correct edge. (Notice the bark inclusion on the other edge)
Beginning arching
I used a Japanese-style pull-saw to cut the approximate height of the plate thickness on each of the corners, so as to avoid unnecessary stress on the corners while carving the arching. It looks a little odd until the arching is complete, but it avoids the possibility of breaking off a corner. I use a large, sharp gouge to reduce the edges and begin the arching; then a toothed finger plane to continue the curves until I am very close to the desired shape. at that point I will switch to a smooth, curved-sole plane and bring the arching to nearly exactly the desired shape. From that point on, a variety of scrapers will be my only shaping tools, for fear of tearing out wood along the figuring .
Here are some photos of the progress. This is very hard, difficult wood to carve, and my hands are giving out, so this is about as far as I am going tonight:
Beginning arching: notice the saw-cut corners, and how the one has been carved almost to a normal curve.
Different viewing angle: The cradle is thick pine, with a plywood door-skin, to secure the plate. Inside, it is cut away, so that the plate can fit arched-side down. The plywood is right at 4mm thick, same as the finished plate.
Continuing arching. Still quite a way to go, but I am getting tired.
So…that is it for today. Pretty fancy wood, isn’t it? The customer bought it in Hawaii 33 years ago, or so, and has dragged it around all these years, until he decided that he wanted a five-string fiddle. Probably the only opportunity I will ever have to make a fiddle out of curly Koa, but it is really going to be a beautiful instrument.
My hands are getting too tired to work effectively. I will try to get more done later this week.
Thanks for looking.
Five-String Fiddle Progress Report #4: Graduation
5-String Progress Report #4
Graduation
Graduation begins with measuring in the spots where it already feels a little thin, so as not to make a fatal mistake and carve right through the plate. (It happens!)
Once I know where I am free to carve, and where I need to take it easy, I begin by carving cross-grain with a medium-large gouge. I check periodically with a caliper. When it begins looking closer to the right shape inside, I measure again, and double check those special spots.
Beginning graduation, using a gouge.
Then I go after it with a toothed finger-plane. This is really just an Ibex 18 mm finger-plane with a toothed blade, and a wooden handle added to save my fingers. I originally added that handle to keep from blistering my forefinger and thumb, as I had done so on every single instrument up to that point. (That was my #16 instrument– a cello.) I was surprised to discover that it also gave me much more power and control so that I was able to set the blade deeper and carve much more aggressively, taking off much thicker shavings.
Using a Toothed Finger Plane to further the Graduation process.
Once it is smooth inside, and within a millimeter or so of completion, I switch to a smaller finger plane and cut more gingerly, until it is all within a few tenths of a millimeter of the goal thicknesses, and then I finish with scrapers. Here is how the plate looks at that point:
Graduation nearly completed– the skewers are only there to create shadows so that the contiour will show in the photograph.
Another view, at a lower angle. There are still a few lumps to smooth out, but the graduation is essentially complete.
Usually, by that point, I am beginning to see the interior of the f-holes, too, because, as you may recall, I had incised them pretty deeply. Once the inside is complete, I finish cutting the f-holes. Many people use a jeweler’s saw, a fretsaw, or a coping saw to cut out the f-holes. I generally just use the knife, except that I do have a special tool for cutting the round upper and lower eyes.
And that is what I will show in the next post…which, hopefully will be sooner this time.
Thanks for looking,
Chet
Five-String Fiddle Progress post #3
5-string progress #3
Arching and F-holes
Last time, I had traced and cut out the top plate, and actually, I began the work on it, thinning the plate to the desired arching height– but that is when I discovererd that there was a bark inclusion that extended right through the upper bouts. So, for those “sharp-eyed” among you, who notice that the grain has changed; Yep. It surely has! Too bad…I liked the grain of the spruce in the plate I first chose, but it turns out it was just a little too interesting.
So, on this plate, all I have done is the outer arching and the layout and incision of the f-holes. After completing the arching, but before final scraping, I laid out the distance from the upper edge of the plate to the “stop” line (where the bridge will stand) at 195 mm, then laid out the distance between the upper eyes at 42 mm. I used a plastic template that I made years ago (cut out of an old flexible face-shield– the kind welders use when they are grinding steel) to lay out the shape of the holes, then incised them deeply with a thin knife. They would have been virtually invisible in the photos, so I traced them again with a sharp pencil after incising them, so that you could see them in these photos.
Arching complete, f-holes laid out and incised.
Arching: Final Check
Next I checked the arching by sighting edge-ways at the plate, to see whether the main stem of each f-hole is fairly parallel to the rib-plane. Usually I find that I have left the arching a little too “puffy” around the lower stem and lower eye area of the f-holes and need to plane away a few more strokes to get the stems lined up. I don’t think the looks of the f-holes are the main issue, here– the shape of the arching is fairly critical to the sound, as best I can understand, and this is just a “marker” for me to check.
Checking to see that f-holes are aligned with rib-plane.
Obviously, this alignment is something I have to do before I try to complete the inside carving, or there might not be sufficient thickness left to do the final adjustment. I try to estimate and get this area as close to correct as possible before laying out the f-holes, but I have had to adjust them at least a little, every time, so far.
After I am satisfied with the overall shape of the arching, I use scrapers to reduce all the lines and ridges left by the finger planes into a smooth continuum.
Graduation: Beginning the Interior
Once I have the outside arching the way I want it, I can start on the inside, and the final graduation of the plate. I hold a pencil in my fingers so that about 9 mm protrudes onto the plate, and then run my fingers around the edges…nothing precise about it: it is just a guideline for carving. I want to leave this area untouched until the last bit when I am scraping the inside, before installing the bassbar. I use the same template that I use for the final shape of the end blocks to scribe the shape of the area to be glued to the blocks. I scribe in the corner blocks with a curved scraper that just happens to fit the shape I want. All this outer perimeter area will be left flat until the last step before installing the bassbar, and/or installing the plate on the ribs. I want just the gluing surface flat when I am ready to install the plate.
Inside carving plan.
Preparing for Graduation: Measure First!
It pays to use a caliper and check the thickness all over before beginning to carve. I do have a mental image of the desired shape of the interior, but I do not have a mental map of the thickness of the plate, so I measure at least the areas that already feel pretty thin to my fingers, and decide how much should come off in each area. As it turns out, this time, no areas are really borderline, but some are within 1.5 mm or so, so I will be careful around those places. I am aiming for about 3.5 mm down the middle, fairing down to 2.5 in the upper and lower flanks. and a few places 2 mm, very likely. I will try to leave some areas a little thick, where there is a likelihood of cracking, but in general, I expect this will be a pretty thin plate…the spruce is a little dense (which I have had good results with in the past), so it can stand to be a little thinner than usual.
After the inside is carved and scraped to my satisfaction, I will complete the cutting out and shaping of the f-holes, then chalk-fit and install the bassbar. I will post photos of all that.
Thanks for looking.
