Many guitar players would like to replace the bridge pins on their guitars with pins made from solid bone. To understand why bone is such a good choice for certain critical parts of your guitar you need to consider what's going on when you play a note. The vibration of the string must be accurately transmitted to the instrument's top, (the sound board), with as little interruption as possible. A heavy bridge and saddle will dampen or muffle the vibrations from reaching the sound board. Some of you will know how a banjo or violin "mute" works. It's just a heavy piece of metal surrounding the bridge. It effectively keeps the string vibration from reaching the sound board and therefore "mutes" the sound. (Lowers the volume). String vibrations would also not pass through a bridge that's too soft, like soft wood, because the soft material would act as a shock absorber. The absolutely best bridge material is one that is both the lightest weight and the most rigid possible!
Bone and antler are very rigid and are also slightly porous which lightens their weight. They are dense, resonant, transfer the sound very well and repel moisture. Bone or antler bridge saddles, nuts and bridge pins will increase the volume and tone of your instrument!
Bone bridge pins come either slotted or "Old Stye" or unslotted, which means there are no slots or flutes in the pin for the string. Very early guitars had the slot for the string in their bridge pin holes and the purpose of the pin was to keep the string in it's slot. Flat-top acoustic guitars only sound their best when the strings are correctly installed and properly seated in the bridge pin holes. There is a thin piece of hardwood, called the bridge plate, inside the guitar's top, directly under the bridge. The ball end of the string is supposed to seat firmly under this plate and to stay there because the string passes up through the slot in the bridge-pin hole and bends forward over the bridge. If this isn't exactly what's happening in your guitar it will affect the tone and volume. In many cases in older instruments, the underside of the bridge plate is so worn that the ball end has pulled right through the plate and is resting on the inside of the top. In extreme cases it can be resting on the underside of the bridge, having worn right through the top! A trained luthier can examine and repair this condition using a telescoping mirror. Theoretically, a properly fit string, notch, and bridge pin would allow the complete removal of the pin with the instrument in pitch, leaving only the notch to hold the string in place!
It wasn't until the 50's that bridge pins became notched and smaller string notches were needed in the bridge-pin hole. Some inexpensive guitars have no notch at all. Some luthiers believe that a slight notch and the old style solid bridge pins hold the string more properly under the bridge plate and produces the best sound. A favorite luthiers technique to solve a loose fitting slotted pin is to install the same pin but with the slot turned 180 degrees away from the string. In affect using the existing pin without using the pin's notch!
So...slotted, or unslotted?
If your guitar won't accommodate the "old style" bridge pins with no notch, it's because your guitar doesn't have a sufficient bridge-pin hole notch. You have to make sure you purchase pre-slotted John Pearse bridge pin sets, or create or enlarge these notches until the string locks in under the bridge plate. Many luthiers use a tiny saw made from a section of jig saw blade. Slotting bridge pin holes is a simple and inexpensive job, but requires finesse and experience, so consider having it done at a professional shop. After sawing, use a small needle file to smooth and radius the slot's top. The notch should be radiused toward the saddle where the string bends as it comes out of the hole. Remember too that each string is a different diameter. Each notch will have to be fit a little differently to suit each string. Getting a string end to "lock in" at the bridge notch is simple, but requires skill and experience, and the proper tools. Also this notching of the bridge may require some refitting of the bridge pins to their tapered holes. It's easy to end up with loose bridge pins that fall out easily after these adjustments. This article was prepared and submitted by Mel Ruller and Gord DeVries at The Stringman which can supply you with a variety of ebony and bone bridge-pins, nuts & saddles.