Sunday, September 29, 2013

The Dead Spruce Scroll

        Another busy, busy week in the shop! The spruce is flying and the arch tops are taking shape!
The blister on my finger is now just a patch of fresh skin and the finger plane that made it has done a considerable amount of new work.

       Monday's repair class this week consisted of a long over due look at the frets and fingerboard of my favorite Stratocaster. In last year's repair class I took some time to re level and crown the frets which took care of the few buzzes and several deep dents in the frets, but left me with very low crowns. So low that the neck felt odd to play. So I have chosen to replace them all together with new medium-tall wire and start fresh. This process began with heating and gently pulling out each of the old worn frets, then lightly sanding the fingerboard to smooth and restore the 12 inch radius.

        After cleaning up the board a bit but leaving its well worn feel intact, I pressed in 21 new frets and gave them a dab of glue for good measure. I have found that the glue seems to lubricate the fret slots and help to fully seat each fret. When pressing each fret is clamped in place for a minute while the next slot is prepared. This ensures the fret seats and stays seated. Once they are all in the frets are leveled with 400 grit sand paper. after all the frets are level to each other they must be crowned, re-shaped, and polished all of which happen fairly quickly if the first few steps are done well.  Next week i will finish off by shaping each end of each fret by hand and polishing them all to a high shine. 

        CAD class is getting increasingly interesting as we begin applying all of the techniques we have learned to our specific field. This week we Learned how to use an image to help draw a mandolin body from scratch in the program. The finished drawing was a hollow body with arched top and back. full 3D rib structure, and f-holes revealing the hollow inside. In the coming weeks we will learn to draw necks and other parts and begin designing our own instruments. 

        Arch top construction class saw the beginning of one of the more difficult aspects of the hand carving for the mandolins. The Scroll...... The elegant carving of the upper shoulder scroll on the f-5 mandolin is what sets it apart from its simpler cousin the A-style. Carving this area by hand is all about being able to see what looks good, judge the grain of the wood, and make what you see happen on the surface. The carving is done mostly with finger planes and gouges, then will be cleaned up with scrapers. Each scroll will be different depending on how each carver sees it and chooses to carve it. Even in well known brands of late, until CNC machine carving each scroll and arch was slightly different, making each instrument unique.

        Along with all the carving we took some time to prepare our side/rib material for bending by thickness sanding them down to about 1/16 inch thick. To achieve this quickly and uniformly we use a time save thickness sander. the pieces are fed through the machine and each pass sands off a controlled amount equally. The finished product is flexible enough for steam bending and still strong enough for supporting the top and back of the instrument. 

Look at all that FLAME!!!!!!!!!

        Before beginning to bend the ribs I had to make clamping cauls that fit to the inside mold's curves. This will ensure that once the rib pieces are bent they can be firmly clamped to the corner, neck, and tail blocks for gluing. The cauls are  made from scraps of poplar cut to shape and line with cork to protect the wood. 

        After getting my scroll area caved up nicely, i took my top wood to a dark room and held it at low angles under a raking light. This allows for seeing slight high and low spots on the surfaces and any ridges left from carving. The high areas catch the light and cast a shadow beneath them. Those high areas arethen taken down smooth with scrapers leaving a smooth curved surface.  The next step on the outside will be to begin sanding it smooth and final blending all of the curves together, but before that happens the inside surface must be carved out and graduated for thickness. 

Light from the bench lamp shines right through the thin re curve area around the edge of the top.

Thanks for checking this out and following along! Tune in next week for rib bending and more! 

Sunday, September 22, 2013

Blisters on Me Fingers!

        Well, another busy week has come and gone! Another week filled with much learning. The shop
was filled with the smell of sweat and spruce as we continued carving the arches into our top wood.

        The week began with more repair work on the school owned acoustic guitars. I finished the new nut and saddle for guitar #38, gave it a full intonation and set up just in time for the first year students to start learning their set up class next week! Ill begin the fret job on my Sratocaster and the in depth repair of my first guitar ( a grocery store catalog Five Star from the mid 60's ) this week.

        Rhino CAD class is picking up nicely as well we have been learning all the tricks for creating 3-D geometry in the program which will allow us to design our wildest ideas for our spring CNC builds.Learning this tech is a real treat and at the same time a challenge for me. I have never used a computer in this way before, and I am very exited about the possibilities this knowledge will bring.

        Arch top class is a bustle of activity with all the carving going on. each person will end up with a slightly different end product as we are carving by hand using our eyes and feeling for consistency of the curves. We also use a contour gauge to check our work against finished mandolins.
        On Wednesday while working my work-study job for the instructors, my partners Eric, Jon, and I came up with and constructed carving cradles for the mandolins. The cradle consists of a plywood ring in the shape of an A-style mandolin, with the inside edge rounded over and the shoulders cut away to accommodate the scroll of the F-style  when flipped for carving the inside. The ring is glued to an MDF backer board and a poplar block is attached to the bottom for clamping to a workbench.  As a further safety a layer of  1/8" cork is attached to the ring to prevent marring of the soft spruce tops. With the cradle clamped firmly to the workbench and the top clamped firmly to the cradle both hands are free to do the carving with skill and precision.

        Using my new carving cradle I went back to work hand carving the arches into my adirondak spruce top. The process was greatly improve after receiving mu custom gouge chisel from Cape Forge. This is by far the best carving tool I have used so far. It is balanced, strong, and razor sharp. The gouge cut through the spruce like butter and made roughing out the arches a breeze!

        Once the arching was roughed in and i was happy with the general shape it was time to move on to carving the re-curve around the edge.  The re-curve is a shallow channel around the edge of the instrument that accentuates the arch of the top and makes the wood around the edge the thinnest part of the top to allow the most movement when playing to produce a strong tone. It is not only good for tone and volume but it gives the instrument a refined look.  I began this step by laying out lines on the top to give a guide for where to carve and what to leave alone. There is a narrow flat ledge left around the edge to give a place for the re-curve to return up to, and leave some area to be routed away later for the body binding.

        Once the lines were established I began carving the channel with finger planes. There are many things to be aware of while making these cuts. The channel should only be about 1mm deep when finished, and the top should be around 2.8mm thick at the bottom of the channel. As I carved away I checked often with a thickness caliper to try and maintain a constant depth. Another challenge to this task is the grain run out of the wood. As I carved around the shape I often had to stop and change directions to avoid tearing and chipping the soft spruce. Once the channel was all the way around and fairly consistent ( mine being slightly deeper than some and a bit thinner in the center) the entire arch of the top had to be re-addressed to blend and smooth it into the re-curve.  This was done using finger planes and steel scrapers to leave a nice smooth arch.

        After all was said and done I had a nice smooth arch that flowed down and back up out of the re-curve to the edge of the top. just a bit more scraping, and smoothing and it will be time to carve the scroll and sand it all smooth! And just to show you that this isn't all fun and games, here a shot of the ginormous blister on my index finger that i got from 5 hours of finger planing! 

Thanks again for reading and come back next week! 

Monday, September 16, 2013

Weeks 2 & 3. Blocks Tops & Carving!

       We are moving right along in our 2nd year guitar courses! These past two weeks we have been busy working on our arch top projects, while learning more CAD skills and working on repairs on the school instruments.

       Today I finished the nut, saddle slot re- rout, saddle, intonation, and set up of the school owned guitar I have been working on and began gearing up to re-fret my trusty Stratocaster!

Once this baby has her new frets she'll play better than the day she was born plus have that nice worn in feel!

       Arch top class has been busy busy these past few weeks. After coming back from our Labor Day weekend, we began by flattening the inside face of the joined top. this was accomplished by hand with a block plane checking on a flat stone with a 0.010" tolerance.  Once the bottom was flat I used the joiner/planer to bring the top down flat and the over all thickness to 5/8" to leave enough for carving.
The shape of the mandolin was traced onto the top wood using the template made the first week. That shape was then cut out with an extra 1/8" around the edge to accommodate the thickness of the ribs and a bit of wiggle room. Cutting around the scroll area proved to be very difficult. The cut was made using a coping saw, and jeweler's saw. While making the cut the saw tends to drift to an angle leaving the face of the scroll out of square to the top. I left enough room to clean it up and square it using files and sand.paper.

The sanding around the scroll is done using a copper pipe cut in 3rd's lengthwise, with sticky back sand paper attached to the inside and outside. 

       Another step to complete was making and shaping the inside blocks. The blocks will give support to the rib structure in the points, neck, and tail areas. I constructed the blocks out of poplar. Poplar is a stable hard wood used for guitar bodies, blocks and bracing. It is a light colored wood that will blend well with the maple, and spruce used in the instrument. The blocks are fit to the inside mold, rough cut to shape, and spot glued in place to the bottom half of the mold. Once the blocks are firmly in place the template is place on the top and bottom sides and the shape is traced on. The final shape is cut on the band saw, and shaped with spindle sanders, chisels and files. The scroll area is cut very closely using a fine cut band saw blade. 

       The next step is to start carving the top! Now we are really working wood! First the top is routed to 3/16' thick around the edge. This will be the starting point for carving and almost the final thickness around the edges. There are steps cut into the outside edge of the scroll increasing to full thickness. Then the top is roughen into shape using a combination of scrub planes, block planes, chisels and finger planes. All the time checking with contour gauges, visually, and by hand feeling the curvature. Each step and tool leaves finer and finer results.  The scroll is left raw until later in the process. 

That's a lot of shavings! And that's all you get till next week! Thanks for reading!