string spacing at the bridge

[Mik Neville]

 I'm working on an acoustic guitar that measures 52.32 at the 12th fret and 53.46 at the 14th fret. Can I use a 54mm bridge on this or would the strings run to close to the fret edges. I'm finding out that 54mm is mostly the standard unless you have the means to make your own bridge. Thanks for the help love this place

[Roger Häggström]

My method to find the spacing for the string pins with the neck in place is as follows:

* I put a piece of low tack tape on the top as close to the position of the saddle I can get.

* With a long ruler, I extend the two edges of the fretboard (or the sides of the neck if the fretboard is not glued in place) by holding the ruler against the sides of the fretboard and mark the position as close to the position of the saddle as possible.

* I measure the distance between the two markings and subtract 1 cm from that measure.

* The calculated distance will give the center point for the two E/e string pins in the bridge.

This will give the E/e strings about 5 mm distance from the fretboard edges where the fretboard meets the body. The nut spacing will be set to a distance of around 3 mm, the spacing will increase down the fretboard.

[Mark McLean]

A good rule of thumb is that the string spacing at the bridge should equal the neck width at the 12th fret.  This gives a good margin of safety to keep the string path away from the edges of the fingerboard.  However, many builders give specifications where the 12th fret width is up to 5% less than the string spacing at the bridge, and they get away with that.  For example a standard series Martin D-28 has a neck that is 1 and 3/4 inch (44.45 mm) at the nut, 2 and 1/8 inch (53.98 mm) at the 12th fret and the string spacing at the bridge is 2 and 5/32 inch (54.77 mm).  You might get away with a 54mm spread at the bridge, but it will be close.  Try drawing it out at full scale on paper.  An important factor is how much bevel is on the fret ends.  If the bevel is minimal you provide more usable length of frets and can have the strings closer to the edge without problems.  Also, your 54mm measurement at the bridge is the spacing of the pins, but you can make the string spacing a little bit narrower at the saddle by having small notches in the surface of the saddle - if you need to cheat a bit.  

[Mik Neville]

Thank you for the replies to my question very informative answers that are now leading me in the right direction. I had thought about notching the saddle just didn't know if that is something one should do although it happens on its own on some guitars. I'm going to do what Mark mentioned here and draw it out on paper to see how it looks before I put it on the guitar. What I'm doing here is installing a pined bridge in the place of a pin less one. So, all the good reads here are a real plus in the confidence department. Mik 

[Mark McLean]

If the original bridge was pinless is there a bridgeplate inside?

If not, you are going to want to add one.

[Mik Neville]

There is a bridge plate installed in the guitar already that is why I decided to go with a pined bridge. Some luthiers I talked to told me it will open the guitar up some hope their wright. I have installed some bridges before, so I have that experience just have never changed one from pin less to pined. I'm looking forward to the challenge. Mik