Wednesday, August 08, 2007

Making a Cigar Box Guitar - Part 4 - the bridge

There are different materials/items used for the bridge but it needs to be a hard material. Some people use a threaded eye hook. I tried it but wasn't happy. I make my own simple bridge using some hard wood like oak or mahogany - a small piece left from the neck will do. I make it about 5 cms long and shape the cross section into an upside down T shape. The saddle part where the strings cross is only about 3 or 4 mm wide. I make it using a small router bit mounted in a drill stand. I cut very shallow grooves (1 mm) about 1 cm apart for the strings to sit in.

I string it up temporary but not full tension and place the bridge in it's approx position. Pass the string through the bottom of the holes you drilled at the base of the neck. You need to find the exact spot for correct intonation. I use a tuner and play one string open and tune it to an exact note (e.g. A) The twelve fret should be exactly one octave higher. I use a screwdriver shaft as a slide for this process as the narrowness makes it more accurate. Place it over the 12th fret and move the bridge either further up or down the box until the octave is bang over the twelth. You can mark it's position if you intend glueing the bridge to the box. I don't usually bother as it gives me the option of fine tuning the intonation whenever I want.

The design of my necks means that there isn't quite enough backwards offset on the neck (like a Fender) to provide enough tension of the strings over the nut. Like Fender I get round this by fitting "string trees" which pull the strings down onto the nut. I sometimes use small screw eyes and thread the string through the eye. Sometimes I make a small metal bar with a hole at each end and two small screws through them into the headstock. The bar presses down on all three strings simultaneously. Once you have these fixed you can string it up and tune it.

These small refinements are something you can experiment with. Once you have the basic box, you'll find little ways of improving them. All part of the creative fun.

More refinement tips to come ......

3 comments:

Ben Newbury said...

great blog hope you keep it up. hope to make a CBG for my grandson soon but will play with it for a while before giving it to him. will keep visiting your blog so keep the info coming ben in UK

David said...

Thanks Ben, glad you found me and do have a go at making one, they are fantastic fun. Just finished another and will post a picture soon. One of my best yet.

Wood Finery said...

Great tip on bridge building. I have been going with the threaded bolt but it's hard to guess-ta-mate the right size. So you end up with a hand full. I've considered making my own. After reading your tip David I think I'll give it a try.