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The procedure is guided by shop owner Mr. Jude Reveley. Tool sharpening and use of hand force on chisels is taught by Mr. John Cameron. This is my second practice in the 8 years of working at Absolute Piano Restoration and the third in my entire life. Hopefully the next one could be a little better. My deep gratitude for these two dedicated masters. Set up a sharpening station. Make sure the tools are very sharp. All blades need to be sharpened constantly through the process, about every 8 to 9 notches. In the middle of each notch, saw a relief cut. It does not need to be deep. The purpose is to prevent wood from chipping. Always keep the original bridge cap around for reference. The side line of each notch is marked according to the original cap. It is more than 90 degrees to the bridge pin line (the three bridge pin holes on the first picture) for strings to go by without touching the wood. Cut into this side line with a sharp knife or thin blade, the corner of the blade right on the bridge pin hole. A 2-2.5mm depth line is drawn on the side of the bridge which is not shown on the pictures. That is how deep the notches will go. Then make a saw mark 90 degrees to the bridge pin line for chisels to go by. Little by little, chisel off the maple until the beginning of the notch is right at the center of the bridge pin holes. The left side of the chisel does not exceed the 90° saw mark. Chisel down until the notch reaches the 2-2.5mm depth line marked on the side of the bridge. The corner of the notch is at a wide angle. Tilt a chisel or a sharp blade to about 45°, cut from the side line to the bottom of the 90° notch just chiseled. Compare the notch with the original cap, adjust the new notch if needed. Be patient, make sure each notch is at the same depth and angle. If the wood grain does not allow a smooth cut, chisel a little at a time to cope with the wood. A thin board as the chisel catcher (second picture) is useful to prevent the sharp blade from hitting the soundboard. The single string area on the bass bridge is shaved with a spokeshave. After all notches are carved, sand the bumpy looking notches with a 220 grit sandpaper. Also sand off any dirt on the notched surface. Burnish the bridge top with a steel rod to make the top shinny. Drive in bridge pins to about 3.5mm protruding above the bridge top. Pictures show before and after the varnish is brushed on the bridge notches. Here we used quick dry semi-gloss polyurethane. This is the bridge tops of an old Blüthner. Note the straight downward cut at the bridge pin holes. It almost looks like a mini square. According to Bruce Clark, engineer at Mason & Hamlin piano factory, this clear/sharp termination of speaking length increases tone quality especially at the high treble.
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