Making the Fingerboard -- 2
This is a vacuum jig I use to hold the fingerboard while I am cutting the fret slots. The "tree" is simply a network of shallow grooves which distribute the vacuum. The gray border is the foam tape which contains the vacuum, and the white tube is the vacuum supply. You can just see the metal pin at the end which is used to index the fingerboard in the correct location.
This shows the fret cutter in operation. The jig which holds the fingerboard has slots cut on the bottom which correspond to the fret scale (I have one for each of the two scales I use: Martin 25.4" and Gibson 24.75.) There is a "finger" in the sliding table of the machine which fits tightly in the slots and thus indexes each slot individually. The table is one linear bronze bearings and slides back and forth under the blade. The blade itself is a screw slitting blade which can be bought from most machine shop supply houses. They come in a wide variety of thickness. I use a .023" which works well with the fret wire I use, and as it has no set, it cuts a slot that is exactly .023". this machine was built for me many years ago by a machinist in Wisconsin, and has worked flawlessly for over twenty five years. I love it. I opted for a single blade cutter since that gives me much more flexibility in making boards with different scales -- all I have to do is make a new jig.
Here are a few of the boards I cut for my current batch of guitars. Total time from raw boards to profiled and slotted boards for 16 boards was about 2 hours.
This photo illustrates a simple but very effective jig. It is designed to drill the holes in the edge of the fingerboard for side dots. These must be very accurately placed to look good. I started with a steel bar about 1/8 x 1/2" and marked out a straight line exactly parallel to the edge. Then, using my fingerboard for a gauge I marked out the locations for the side dots, and drilled a 1/16" hole at each location. I mounted the bar on a flat board which was in turn mounted to a wide board. I drilled through the board attached to the metal strip, and installed two toggle clamps on the wide board to hold the fingerboard in place (a pre-set stop ensures that the fingerboard is precisely located, and shims ensure that a fingerboard of any thickness can be centered on the holes in the metal strip.) It is then a simple matter to clamp in the fingerboard and drill the holes. It takes perhaps 15 seconds per board.
The next step is to carefully finish the top of the fingerboard. Earlier I noted that I cut the arch on the fingerboard on a shaper. Now I mount the fingerboard in a vacuum jig to hold it very firmly and work it with sanding blocks having the same radius as my cutter (14"). ( I get these from Stewart MacDonald) This removes any cutter marks left from the shaper. I work the board down to a 600 grit paper.
After the sanding is done I run a triangle file very lightly along each edge slot. This has two benefits. First, it removes the sharp edge of the slot and seems to assist the fret to go in easier. Second, when the guitar eventually needs refretting there is less likelihood of chipping the fingerboard when the old fret is removed.
Here I am using the press to install the frets. This works very well and gives a very uniform fret job. It would be less effective if I wanted to install the frets after the fingerboard was mounted on the neck or after the neck was glued into the body. Each of these methods has its benefits and disadvantages - truth be known I do it this way largely because that is the way I started and simply have grown accustomed to the method.
Here is the completed fingerboard with the tools I use - a brass hammer, an end nippers for cutting the fret wire, the triangle needle file and a coil of fret wire. I prefer to buy the wire this way because there is no need to pre curve the wire before installation - it is already curved. We buy a lot of fret wire and this is the most economical method. We buy most of our standard fret wire from the Martin company and get it in about 5 tang widths, which is essential for a repair shop.
The next step is to glue the fingerboard to the neck.
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Minneapolis, MN. 55404