The bridge of a violin is a piece of wood located on the face of the instrument between the f-shaped sound holes. The bridge on your violin serves dual purposes. It holds the strings in position, ready for playing, and it transmits vibrations from those strings during play to the instrument's body. To have the bridge perform as needed, you have to cut and fit it precisely into place. Mistakes in the process can lead to both awkwardness of play and degraded sound, while success in the process creates a high-quality sound.
Cut the feet of the violin bridge blank to fit your violin. Tape a 5 cm (2 inch) wide piece of sandpaper onto the face of the violin, grain side up. Centre the sandpaper with the cross cuts of the f-shaped sound holes of the violin. Place the bridge blank onto the sandpaper, centred with the width of the violin and run the bridge up and down the sandpaper to grind the bridge feet to the contours of the violin.
Remove the sandpaper from the violin.
Cut the height of the bridge to suit your desired string height. The height of the strings created from the bridge height determines the strings' tension. Cut the height of the bridge between 31 mm to 35 mm (1 7/32 to 1 3/8) in height with an arch of between 12 mm and 20 mm (1/2 and 25/32 inch). Cut your bridge higher the heavier your instrument is, with low bridges cut for more responsive lighter instruments.
Cut the curve of the arch of the bridge so that it equals the curve of the fingerboard, with the G-string side 5 mm (3/16 inch) higher than the fingerboard and the E-string side 4 mm (5/32 inch) higher. The higher you cut the arch, the greater the string tension translated into the violin body, with too much tension increasing the chance of breakage.
Cut the grooves for the strings slightly into the top of the bridge, placed equally 34 mm (1 1/3 inch) apart along the bridge.
Tune the bridge by cutting the kidneys (the holes in the bridge sides), the heart (the heart-shaped hole in the centre of the bridge) and the lower arch of the bridge to adjust the mass of the bridge. Adjust the bass of the violin by thinning the bridge for more bass, or rounding the top of the bridge to reduce the bass. Thin the kidney and heart holes of the bridge with sandpaper to further enhance the bass sound of the instrument. Adjust the high upper sound of your violin by creating a higher arch in the space between the feet of the violin.
Loosen the strings and move them to the sides of the violin. Fit the bridge to the face of the violin by placing it with the feet of the bridge centred between the cross-slots of the f-holes. Make sure that the bridge sits above the bass bar and the soundpost located in the inside face of the violin.
Place the strings into the bridge grooves and tighten them to keep the bridge in place. As you tighten the strings, the bridge will pull forward toward the pegs. Adjust the bridge as it moves to keep it in position and placed perpendicular to the face of the violin. Once you've placed the bridge, tune the instrument for play.
When making adjustments, apply the smallest cuts possible as some sound changes may occur with only a millimetre of change to the bridge.