StewMac Router Base Adapter
Source: Guitar Building Articles/The Guitar Top
For information on different types of rosettes that are typically used with guitars see the article Guitar Rosettes.
Tools and Supplies Needed:
Dremel Moto Tool 4000:
Dremel Router Base
Rosette Forms
Titebond III Glue
Duco Cement
Portable Block Sander
Plastic Tipped Hammer:
r
Plastic or Wood Purfling
Plastic Push Pins
Acoustic Guitar Assembly:
For an acoustic guitar we first need to assemble the rosette rings. If you wish, you can utilize the rosette ring design directly off the guitar plans. If not, design your rosette and make a form for the center rosette if it is to be built up from layers of purfling. The form should match the inside diameter of your rosette. Note that the rosette form consists of a 1/8″ thick wood disk that is fastened to a plywood base.
Measure the length around your form and cut the purflings so they wrap around the form and leave about a 1/2″ gap at the top. (this gap will be covered by the fingerboard). To keep the purfling from sticking to the form, use parafin wax on the form surfaces.
Take your wood or plastic purfling and apply the appropriate glue. (Titebond for wood and Duco Adhesive for plastic.) Start at the top of the rosette, which is the portion that will be beneath the guitar fingerboard and slowly form the purfling around the form, using either plastic push pins to hold it firmly against the form or small finishing nails with a plastic tipped hammer. Continue this until you again reach the top. Set aside to dry.
Layout your rosette precisely on the guitar plate using a compass. Now drill a 1/4″ hole in your guitar plate at the center of the rosette radius. Insert a 1/4″ bolt through your Guitar Workboard and fit the top plate over this bolt. Now chuck a carbide or diamond router bit in your Dremel and attach it to the router base. Double-check all of your cuts and work slowly. Be especially careful when you are routing almost parallel to the grain as the bit can tend to tear out some of the soft grain. Your cut depth should be about half of the top thickness.
Now remove the rosette from the form and carefully check it against the routed channel. It should be a tight fit and the rosette should not just drop in. You should have to tap it lightly with a plastic tipped hammer. Once you have the routed channels exactly the right widths, apply some glue to the rosette materials. Again, use titebond for wood and Duco Adhesive for plastic. Tap the rosettes until they are protrude very slightly above the guitar top. Set aside to dry.
When dry take a very sharp scraper and cut the rosette down to the surface of the guitar top.
Potential Problems:
When using pre-purchased wood purfling you may find that you cannot make the radius without it cracking. If that is the case, soak the wood in very hot water (not boiling) for about 10 minutes). The wood will now be flexible and easily will make the radius.
Classical Guitar Assembly:
If you purchase a pre-made rosette, carefully mark the inside and outside directly on the guitar top plate with a compass.
Using the Dremel and a router base adapter, cut the rosette channel. The depth should be slightly shallower that the rosette depth.
Again, check your fit several times. You should have to lightly tap the rosette to get it to fit into the channel. It should not drop in without any force.
Once fit, apply a small amout of Titebond glue and fit seat the rosette with the plastic tipped hammer and a small block of wood. Set aside to dry overnight. Take a very sharp scraper and scrap the surface of the rosette level with the surrounding guitar top plate.
One final operation to do while your top plate in still on the assembly board. Take the router and cut out the sound hole. Make the cut with 2 passes so you don’t burn the wood and go slow.
Tags: guitar assembly, guitar making, how to make a guitar, install guitar rosette
