f.j.w. -> Action and bridge height (Jun. 2 2017 15:48:50)
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Hi All My first flamenco build is progressing. I have put in the rosette and joined the back. Now I have to begin to construct the neck, and I have to decide the neck angle. As I have explained earlier I am a violin maker, and this is the first guitar that I am making. So I have a lot of beginner questions and you guys have been just amazing in regards to your willingness to share your knowledge. Thank you so much. Here is my next question. It is about the relationship between the bridge height and action. Just to be sure. I measure the action as the distance between the bottom of the string and the top of the 12th fret on the open string. I know that some people measure the action with the string stopped at the first fret, and there are VERY good reasons for doing so, but is seems that measuring with the string open is more common. The difference is exactly 0.2mm when I measure my teachers guitar. This is significant. I have read the foro archives and there is a lot of talk about the action on the 6th string. It seem to be the consensus that the action should be between 2.8mm and 3.0mm. I have decided to aim for 2.8mm. However there is nearly no mention of the action of the first string. On practically all the guitars I have ever seen the action is lower on the first string than on the 6th string. My question is then, what action would you recommend on the first string if the action on the 6th string is 2.8mm? My other question is this: What should the string height be at the bridge? In the foro archives there are a lot of discussion of the string height at the bridge, and it the general rule seems to be that the string height should be between 7mm and 8mm, or the thickness of a cigarette. According to EU regulations the diameter of a cigarette must be exactly 7.5mm. However no one specifies the exact string height at the bridge under the 1st string and under the 6th string respectively. Does this mean that the string height under all of the strings are the same? On my teachers guitar this is not the case. The string height is 6.4mm under the 1st string and 7.6mm under the 6th string. A difference of 1.2mm, is this normal? My next question is how the string height at the bridge and the action correlate. If the action is 2.2mm at the 1st string and 2.8mm at the 6th string, then the difference of the string height at the bridge must be exactly 1.2mm (if the fingerboard is even thickness). This is how my teachers guitar is. However if the string height at the bridge is the same for all of the strings, then the difference of the action must be created by making the fingerboard thinner under the 6th string. To achieve a difference in action of 0.6mm the fingerboard must be 0.6mm thinner under the 6th string than it is under the 1st string at the 12th fret. Of course the thickness of the fingerboard must be the same at the treble side and the bass side of the fingerboard at the nut end. This is not the same as the difference in the thicknesses of the edges of the fingerboard at the 12 fret, since the fingerboard is wider than the neck, and therefore the difference in the thickness of the edges must be little greater than 0.6mm. So what is the normal way to do this? Option 1: To create the difference in action by making the bridge higher on the bass side. Option 2: To create the difference in action by making the fingerboard thinner on the bass side. Option 3: A combination of the above by making the bridge a little higher on the bass side, and making the fingerboard a little thinner on the bass side. This may seem like splitting hairs, but the difference between a good set up and a bad set up is only a hairs width.
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