Here I will be replacing a fixed bridge with a floating tremolo system. This is a modification that was very popular years back when locking trems first came out but one I don’t do very often these days. Our starting point is a Carvin Strat type guitar with a typical hardtail bridge.
After removing the bridge and all the electronics, I need to plug the two mounting holes at the front of the old bridge. They are not exactly where I need my new pivot post bushings and in fact will be right at the edge of them when finished. The holes are drilled out and some small maple dowels are glued in. Now I can put down some tape and start to layout the position of my new bridge. A lot of folks would simply layout using the mounting holes of the old hardware as reference. I instead prefer to layout based on the neck. First I mark a line from each side of the fretboard. I then pull a parallel line from the frets and use my compass to divine the centerline. I then measure out my scale length and compensate for the offset between the pivot center and average saddle peak to find the line my studs will mount on.
Now I can attach my acrylic template to the guitar to guide my router. The template attaches with two screws that also will serve as the center points for my pivot bushings. I carefully align the template and use a self-centering bit to drill pilots for the mounting screws. I drill one, put the screw in and then drill the other. The layout tape is then removed and the template attached for the cutting operations.
The neck can now be pulled off and the body clamped to a bench to begin cutting. I use a plunge router for this with a solid carbide downcut spiral bit with a guide bushing to waste out the material. I make a series of cuts at quarter inch increments until I am within about ½” of coming through the body.
After this operation, the template can be pulled and I can move over to the drillpress. With a forstner bit I will drill a hole through the back aligned with the forward treble corner of the cavity I just cut. This will serve as a reference point to align my template on the rear of the guitar to cut the spring cavity.
I will also drill the two holes for the pivot stud bushings while I am here. The less walking around the shop I do the better. Notice how close the new holes are to the ones I plugged.
My back template is aligned and attached in a similar manner to the one on top. It also attaches with screws, which serve as cover mounting holes in the end. A new hole for the ground wire to the bridge is drilled as well as holes for the spring claw. After all the machining is done, I take the body over to my big buffing arbor and give the whole body a quick polish to remove any slight marks that may have been left from the work. Now it is just a matter of installing the hardware and setting up the guitar. Here is the finished project. With just a few hours work it is a whole new guitar.
Originally published in Brian Howard's Guitar Building & Repair Blog.