Wednesday, February 15, 2012

How to Glue on a Classical Guitar Bridge

Wood is our most versatile, most readily available building material, and a general knowledge of the physical characteristics of the various woods used in building operations is extremely desirable for the carpenter. An intimate knowledge of this subject is only attainable through long experience.

Harry F. Ulrey, Audel's Carpenters and Builders Library No. 1, 1972


Gluing on a guitar bridge is as nerve racking as routing out the binding channels. Placement is important: the proper distance from the nut with compensation (652mm is what I like to use); measuring that the bridge is parallel to the 12th fret and that the holes for the first and sixth string are parallel to the fingerboard. I grow nervous as I do the measurements, I want the bridge to be in the proper spot, it makes you sweat. (See Cumpiano's book for full details on gluing down a bridge)



It takes several tries to get the bridge to align on all 3 parameters and then you have to hold the bridge in place with your "off" hand while you scribe a faint line with a razor knife with your "on" hand. (Sorry for the horseman terms, I just can't say use your left hand to hold down the bridge and scribe the line with your right hand, that would be politically incorrect on my part.) Above photo shows that the bridge has been marked.



Now you carefully place masking tape adjacent to the line and build up three layers, the tape will help hold, or capture, the bridge in it's proper position.


You have to recheck all 3 of your measurements before you glue down the bridge.


Clamps, a gluing caul and a Charles Fox bridge gluing jig from LMI.


I did a dry run with the Stew-Mac bridge clamps and decided against them, they kept twisting the Fox clamp out of position. The caul has been taped to the inside of the sound board.

I used Titebond to glue the bridge and some homemade cam clamps, they don't twist the Fox jig out of position. Notice the wedges placed underneath the backs of the clamps, this is done to keep the clamps from distorting the sound board.

Whoops! I forgot to include a photo of the bridge after the clamps were removed. Next post!


Check out Jonas Nordberg playing a theorbo, aka "monster lute". It's a gorgeous clip.

3 comments:

  1. That lute must be hell to take on an airplane!

    Clamps that work with screws invariably make the piece under them creep. That is why I use mag-jigs for my band saw and drill press fences: once in position the clamping force creates no distortion. For luthier work, how about a clamp that, once in position, creates downward force from opposite magnets being activated, pushing away from each other, rather than pulling toward a piece of metal?

    ReplyDelete
  2. Tico:

    Your idea for a mag clamp is intriguing, I've never worked with magnets before, other then grade school science experiments. I'm open for any suggestions.

    ReplyDelete
  3. My lute, be still
    for I have done.

    Thomas Wyatt, My Lute Awake

    ReplyDelete

What a Concert Classical Guitarist Says About My Guitars

  I have had the pleasure of playing the magnificent guitars made by the luthier Wilson Burnham. The first impression that one perceives is ...