The
meeting started out with a demo on gluing on an acoustic bridge.
Morning rain and cold weather caused us to move indoors again. We
concentrated on the correct procedure for bridge placement, clamping,
and gluing techniques. The use of a CNC mill for nut sizing and
slotting was demonstrated. Headstock machine head alignment, Break
angle and string spacing were also discussed.
Subjects covered in this meeting were:
Nut spacing
Nut slotting
Nut break angles to the machine head shafts
Headstock rake angles
1. Jim's Rickenbacker Model
730S "Shiloh" was a factory second bought through a special program for
a now defunct organization which shall remain anonymous.
Since the neck rake angle was a little over 3 degrees it was necessary for Jim and Gary to build a custom bridge out of coca bola. Notice the abnormal bridge pin slots designed to apply the same string pressure on the saddle for all six strings. This creates better string balance, even string energy and an equal dynamic force of vibrational energy through the guitar top. |
 2. Holes are drilled for some sacrificial plastic bridge pins. These pins will stabilize the bridge so it does not slide around when glue and clamping pressure are applied. The pin heads will be cut off to make room for the clamping caul. The holes will be redrilled once the glued bridge is dry. |
 3. The bridge location has been scuffed and cleaned in preparation for the gluing process. |
 4. Tape has bee applied to determine the correct bridge placement. |
 5. Bridge placement ready for clamping caul. Notice the top of the bridge pins have been snipped off to make room for the caul. |
 6. Caul dry clamped to check that the outer edge pressure is equal to the center clamping pressure. |
 7. Another view. |
 8. Example of a CNC program using G codes for x,y,z, axis control. |
 9. Setting up the mill usually uses up the most time in the CNC process. |
 10. Checking the starting alignment. |
 11. The proverbial test run, again! |
 12. Sometimes the programing snafu's are enough to make you want to eat your keyboard. |
 13. Finally some results. |
 14. Cone shaped slotting cutter allows for a cleaner cut and less bit breakage. |
 15. In bone chipping at the edges can be a problem. The name of the game is always... speed and feed! The speed/feed rate always determines the results of how clean a cut can be. |
 16. The end result of this process is a nut that is exact in it string spacing so the player can feel an even tactile response between string centers. |
 17. Steve tries his hand at programming. |
 18. Calculating the nut width. |
 19. String spacing and machine head holes must align properly to obtain a straight sting pull through the nut. |
 20. Checking the slot depth. |
 21. Our long scale mandolin is presenting it's own set of problems for machine head placement. |
 22. If Shawn uses what is in his mandolin method book, he will have string hitting other strings on their way to each respective machine head post. |
 23. Shawn, freehands the shaping of the headstock on the oscillating drum sander. Don't worry Gary showed the correct way to use a riser block to sand the hard to reach areas. |
 24. Hmm! This one looks different from mine! |
 25. Now Shawn's cooking with gas. |
 26. Ok, so it looks pretty good. Don't get a fat head about it. There are still many more mistakes to be made and corrected. |
 27. Gary is checking Jim's top bracing on he Ramirez classical project. |
 28. The master minds at work. There are many minds here but nobody's mastered theirs yet. |
Subjects covered in this meeting were:
Nut spacing
Nut slotting
Nut break angles to the machine head shafts
Headstock rake angles