Tools and Materials:
Dremel Rotary Tool or Bosch Colt Palm Router
Binding Router Guide, or Rabbeting Bit For Bosch w/ Bearing Guides
Downcut Router Bit for Bindings
Japanese Pull Saw
Duco Cement for Plastic Bindings
Titebond for Wood Bindings
Routing the Channels:
I would strongly suggest that you use a Dremel Rotary Tool or the Bosch Colt Palm Router, along with a Binding Router Guide for the Dremel or a Rabbeting Bit for the Bosch. For optimal cutting with the Dremel, use a down-cutting CNC bit which will leave a clean cut and flat bottom, along with enhanced cutting speed.
I have tried using standard routers and router attachment with less than expected results. The two-handed routers are usually too big to horse around a small object like a small headpiece let alone a body and besides, if you can’t see exactly what you are doing, a channel error surprise is not a pleasant thing to deal with.
With the delicate use of the Dremel and the Binding Guide, or the Bosch Colt, you can keep a close eye on your work, pause without worrying about inconsistencies and micro-adjust your channel almost on the fly. Also if you decide to use the Colt Router, unless you really screw-up with placement of the router on the headpiece, you can have the router in any orientation you like and it will not matter as the bearing guide allows the same cut distance for 360 degrees.
The Trial Run:
Whenever you cut binding channels, you should do a trial run on a scrap piece of wood. I keep hardwood scraps around
the shop for just this purpose. Also, you can just as easily do this on a scrap piece of plywood.
Just chuck up your router bit, screw on the Binding Guide and set the depth and width of the channel by holding the binding on the bottom of the Guide and micro-adjusting the depth and width of cut. Start out a little shallow on the width and depth of this cut.
Make your trial cut and test the end of your actual binding in the groove. Make adjustments until your binding/purfling is about .5mm above the surface of the wood and dead-on even with the width.
Clamp the neck in a sturdy woodworkers bench vice and make sure there are not any obstructions around the routing work area and the headpiece is well above the work bench.
Fire up the router and start in about halfway down one of the straight edges of the headpiece. Very slowly work your way around the headpiece and when you turn corners try to keep perpendicular to the workpiece so you are not cutting at an angle.
Make sure you stay perfectly vertical and apply very little forward pressure. It is import that you let the router bit to the work without burning through the wood. you can also tell by listening to the RPM of the Dremel if you are moving too fast. The Colt has more than enough power that you don’t have to worry about cutting speed.
Once you have cut all the way around make a second pass to pick up any inconsistencies that you may have had in the first cut.
Get out the Masking Tape and cut about 3 dozen or more 3″ strips on place them on the edge of your work bench or other convenient place at arm’s reach.
For Plastic Binding use the Duco Cement. A caution here – this stuff sets up fast so you have to work efficiently. I usually apply the cement to about 1/2 of the binding, then set the binding and then glue the other half. Also wear plastic glove or latex glove to prevent this adhesive from soaking into your skin.
Since you have your binding pre-bent. Apply the cement to the top, the top two curves, if you have them and about half-way down the sides.
Slide the binding into the channel and take a piece of Masking Tape in one hand, and while holding the binding straight and in-place with the other hand, pull the tape very tightly over the binding. I find what works best here is to attach the tape to the bottom of the headpiece and pull it up and over the top.
This holds the binding the the channel without tipping it and then gives you a good, firm downward pressure on the binding. Secure the tape to the top of the headpiece.
Continue all the way around by placing strips of tape about 1/2″ apart. When you are through securing the binding. Infill the spaces with additional tape and address any stubborn areas.
If you are using wood bindings around the headpiece, use the exact same procedure as outlined above with the exception you use Titebond glue in lieu of the Duco. Also the dry time of the Titebond allows you to apply glue to the entire piece at one time.
Also, with wood binding and sharp corners. I try to avoid miters whenever possible. As the instrument wood shrinks a bit the first place you will notice this is at a miter joint. Usually wood binding will have a feature purfling installed prior to the binding installation. As you can see in the top photo of this post I actually used a black/white purfling prior to installing the binding.
These purfling strips are installed in separate gluing operations. I usually install the long sides of each side of the headpiece first, with the strips slightly longer than needed. Set it aside and let dry. When dry sand the veneer end flush with the channel. Next install the top of the veneer and the transition curves from the nut. Again leave these slightly long and when dry sand ends down to face of installed veneer.
Repeat for additional lines of purfling. When installing the binding use this same technique. This will make all of your joints square and not mitered for a much more durable joint. If the small amount of end grain at the joints doesn’t bother you this is a great method to eliminate unsightly pulled apart miter joints.
Scrape the Binding
The next day, carefully remove the tape, being careful not to remove any wood fibers with it. Take a small sharp scraper and gradually plane down the top of the binding/purfling until it is completely flush with the top of the headpiece veneer. Do the same with the sides, being careful to hold the scraper parallel to the work. If you would like to thin the line of the binding around the entire headpiece, this is best done on a stationary drum sander or a drum sander mounted in a drill press.
What to do with the gaps! OK we are not all perfect, especially me. Sometimes, despite all our good intentions and planning, there are, to our surprise small gaps between the binding and wood. An easy way to address this is to work a small amount of Titebond into the crack with your index finger. Clean off the excess glue from the wood and binding material.
Now take 220 sandpaper and sand the surrounding wood, being careful not to get crumbs from the plastic if it is a plastic binding.
Work the dust into the crack to mix it up with the glue and let dry. Finish sand and the crack disappears.
The Final Cut:
Finally take the Japanese Pull Saw and cut the binding/purfling square and flush at the guitar nut. Note you may decide to hold off on this until the guitar neck is fully shaped, fingerboard installed and you are ready to install the guitar nut.