Crafting the bridge


Click on any picture to see a larger image...
Here's the target--a nicely crafted (sculpted?) bridge that is on Dan Biasca's completed guitar that's the model for the guitar being built in this class.
The bridge started with a slab of Ebony approximately 3"" wide by 7" long by 1/2" thick. First, one flat was established by planing one side, and the piece was thickened to just slightly thicker than 3/8". A template of the plan-view shape of the bridge was drawn on the surface of the slab, then the rough-cut piece was double-sticked to a pattern for final shaping.
Here, the piece is being final shaped by cleaning up the rough piece using a pattern bit on the router table.
While the top of the bridge is still flat, a slot for the saddle is cut in the bridge. Note that the slot is angled--it is skewed away from the fingerboard by 1/8" to compensate for increased tension when a string is pressed against a fret. If this isn't done, the tones would be slightly sharp when the strings are fretted. This slot is accomplished by using a 1/8" router bit in the drill press. The back of the pattern (next to the fence) is skewed at the right angle.
Here is the bridge, with the slot cut but before carving the shape on the top of the bridge.
To carve the top shape, I began with a flat file and created a fingerboard-to-end curve. the diameter of the curve will probably end up being about 2" or 3".
Once the front-to-back curve is completed, I installed a domed fence (25' dome) 1/8" away from a spindle drum and very carefully fed the ends of the bridge into the drum. I had to move slowly to avoid stalling the drum.
Finally, I used a 1/2 round file to sculpt in some additional curves as shown, and sanded up to 400 grit. This is now close to the final shape, and the holes for the string pegs will be cut after the bridge is installed on the guitar.
Elapsed time for these steps: 6 hours ... See the main page for the cumulative time.  
It's been a while since I've worked on the bridge; I set it aside while I worked on the guitar body. The guitar body is mostly finished, awaiting polishing now and the next step will be to attach the bridge. Before I do so, I need to complete the final finish on the bridge. My last work on the bridge was to complete the general shaping. On close inspection, some additional final shaping is required, so using a combination of chisels and increasing grades of sandpaper, I carefully cleaned up the shaping, ensuring that the bridge shape looked symmetrical.
Once the final shaping was completed, I applied finish to the bridge. I chose to use Tung oil. Here, I've applied the first layer of Tung oil. I applied it unthinned, and wiped it off of the surface with a cloth. This showed a few file marks that hadn't yet been sanded. I cleaned up these marks and lighlty buffed the surface with a synthetic wool pad. It looks pretty nice. I'll let this first layer of oil dry about 4 hours, and then I'll apply a second layer of oil, buff it in lightly, and let it dry overnight before final buffing.
Elapsed time for these steps: 2 hours ... See the main page for the cumulative time.  

The next step--Attaching the bridge >>

<<Go back to the main page