The bridge plate serves as a reenforcement to the top to help prevent bellying and add another layer to stand up against the string tension. A bridge plate may not be a standard “wear” part, but it is only a matter of time before this part requires repair or replacement. As the string balls slowly dig in-between the bridge pins and the plate, they will begin to enlarge the hole and wedge between the pin and plate causing damage to the surrounding wood. Aside from potential damage to the top, this will allow the string to pull up further. When this happens the winding may come across the saddle. This will cause intonation issues and will not let the strings vibrate at a consistent pitch up and down the fretboard.
Enlarged string holes in the bridge plate do not always require replacement. When possible, we prefer to repair the original bridge plate. This can be done with special tools that allow us to replace the worn sections or we can add a brass plate that reinforces the bride plate.
There are also times a bridge plate will need no repair other than to be glued back into place after it has come loose. While this sounds simple enough, cleaning a failed glue joint and reattaching the bridge plate is no small task when done through a sound hole.
An acoustic guitar bridge plate can be made of spruce, but more commonly will be rosewood or maple.