Okay. First things first. Before you glue on the bridge for an acoustic guitar, the entire guitar needs to be finished and buffed out first. In the past, when I first entered into guitar building, I started applying my guitar bridges on the guitar and then finished over them. While this is an accepted practice for classical guitar construction, I would not recommend it for acoustics.
Prior to finishing your guitar, simply apply a masking tape mask-out to conform to the bridge shape (keeping it about 1/16″ to 1/8″ in from the actual bridge outline. Once the guitar is finished, you can cut the edge of the masking tape and zip out the mask. You are left with bare wood on the top plate on which you can easily glue the bridge.
Tools and Materials:
Adhesive Sandpaper 120 Grit
Titebond III Glue
2-Part Epoxy Glue
Gorilla Urethane Glue
Acoustic Guitar Bridge Clamp
Woodworkers Marking Knife
Wood Chisel Set
Roughen The Wood Surfaces:
The top plate will be very smooth from finish sanding with 220 Grit sandpaper. To make the glue stick a bit better and have more surface to adhere to, I prefer to take some 100 to 120 grit sandpaper and rough things up a bit.
Also if the bridge material is Rosewood, you will want to clean the gluing surface of the bridge with Acetone and a cloth. Keep cleaning the wood until no more color comes off.
Note: Acetone if very dangerous to work with. Be sure to use the proper protection of rubber gloves, an N95 respirator and eye protection. Also be sure not to work near spark or flame as it is extremely flamable.
Bolt The Bridge In Place:
Place the bridge in place and carefully mark the center of the holes for the 1st and 6th bridge pins. Drill holes through the top and bridge place, being careful not to rip through the bottom side of the bridgeplate.
Next take a couple of stove bolts and place them in the 1st and 6th string bridge pin holes and secure the bridge to the top.
Check for fit around the perimeter of the bridge to make sure the bridge either lies flat or can be pushed flat with gentle pressure.
Glue Bridge In Place:
The best method to secure the bridge to the guitar top is with the GLSS Bridge Clamp. This is a jig that I have developed over the years to more easily glue bridges and more importantly, give you greater ease in the glue cleanup after the bridge is clamped
You don’t of course need to use this clamp and use the more traditional 3-cam clamp arrangement, but the little bit of work and material that is required to make it will be well worth the effort.
Selection of Glues:
For bridges, I have gravitated toward the Urethane Glues, like the Gorilla Glue. I have found that this glue is very tough and resiliant. Many luthiers use assorted glues for bridges including, Titebond and Epoxy. That, of course is your choice. You will find that if you use a Titebond with one of the oily exotic woods, the bridge will lift much quicker over time.
Spread a very thin layer of glue on the bottom of the bridge and the guitar top surface. Carefully place the bridge and attach the gluing jig and simply tighten the bolts. First the bolts that go through the pin holes. Then the blots at the string ramps.
Once the bolts are tightened, you will get glue squeeze-out around the entire perimeter of the bridge and you should take a small Wood Chisel and clean it up. Follow with a rag with glue solvent and carefully finish up the clean-up.
The next day remove the the bridge clamp and do a minor amount of last minute cleanup.