Unless the position of the saddle on a steel string guitar is properly adjusted, the instrument will tend to play out of tune. When a string is pressed down against the fretboard the string is stretched out a little bit. This increases the tension of the string, raising the pitch of the note being played beyond the desired pitch. To correct this problem it is typical for a guitar to use a compensated saddle, meaning that the saddle is placed a little farther back from the nut than the scale length would dictate. In addition, the lower thicker strings need to have more compensation than the higher thinner strings. The low E string is usually about 1/8 of an inch longer than the high E string. This is accomplished by mounting the saddle in the bridge at a small angle. Individual strings lengths are fine tuned by filing the top of the saddle to move the break forward of backward. However, once the saddle is compensated the intonation cannot be easily changed without replacing the whole saddle.
To improve the intonation on its guitars, The Portland Guitar Co. employes a system called "The Variable Intonation Split Saddle Bridge." The standard solid saddle is replaced by a saddle blank cut into six separate pieces, one for each string. The separate saddle blocks are placed in a channel so that they can be moved forward and backward until the best intonation for each string is found. Furthermore, as the guitar ages, the environment changes, or if a different type of string is used, the intonation for each string can be measured and adjusted to its optimal position. In addition if a standard tradition saddle is desired, one can easily be installed.
Portland Guitar's Split Saddle Bridge gives you the opportunity to set the intonation of each string individually. Each saddle will slide back and forth in its T-slot changing the effective scale length, and thereby compensating for the effects of fretting the string. With the strings at full tension the saddles are held firmly in place by the force of the strings and a special tool is provided so they can be easily adjusted. When the strings are removed the saddles will stay in place unless they are inadvertently moved.
To adjust the intonation on an individual string, position the tool so that the string passes through the slot in the tool and the tip of the tool is touching the lower edge of the saddle. Push on the tool so that the force is applied to the bottom edge of the saddle and in line with the string. Move the saddle back and forth until the best intonation is achieved. The guitar will need to be tuned after the adjustment is made.
Each saddle is fabricated so that it slides in a complimentary T-slot.