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The Neck

The Neck

The neck on a classical guitar must be stable and strong without being overly heavy. The traditional choices of wood for a neck are mahogany and Spanish cedar. Both are very stable and have a good strength to weight ratio. The main difference being that mahogany is a bit more dense then Spanish cedar.

On steel string guitars where weight is not as much of a concern I have seen walnut, maple, and even nara used with success. On a steel string guitar strength and stability are everything since the string tension on a steel string guitar is far greater than that of a classical guitar.

The neck and the top directly absorb all tension of the strings. Both are important and wood selection should be considered seriously to ensure that your instrument will not develop severe problems as it ages.

Choosing the Wood

neck-blanksOne of the most important features of the neck is stability. The neck should not warp, twist, cup or bow as it ages. It needs to be able to stand up to the tension of the strings throughout its life.

Some wood has a tendency to bow or cup after it is re-sawn. The reason for this typically has to do with the way the tree grew and where in the tree the neck blank came from. A cut taken from a tree that had a slight bow to its trunk will result in a piece of wood that will want to retain that shape when thinned down.

Checking for Tendencies

You can check for these tendencies as you prep the neck blank for use.  Mill the neck blank making sure to take some wood off on both sides, but leaving it thicker than you need. Then let it sit for a few days. Come back and put a straight edge on it to see if there is any bowing or twisting. If there is a bow of more than 1/32 and of an inch I would consider finding another piece for the neck blank. And if it has twisted at all I would not use it for the neck blank.

If the changes have not been too severe ( no more than 1/32″ in the middle) you can use this piece for the heel stack. The pieces for the heel stack are only be about 5 inches long. The bowing or cupping will be minimal over this length and be considered negligible. The pieces are glued on top of each other so any movement is unlikely.

Strength and Runout

runout on a piece of woodThe wood for the neck blank should also be strong. To assure the neck is strong you need to select a piece that has minimal run out. Run out can be seen in the side grain of the neck blank ( see photo on right). The grain lines should run parallel to the surface. Perfectly parallel grain lines are difficult to find so it is likely that the lines will angle toward the edges. If this is so you want to make sure that if the grain lines run from one face to the other, they do it over a distance of 5 inches or more. If the side grain runs from top to bottom in a short distance, say an inch or two, this is what is known as short grain and is weak to shear force here. Any piece with short grain should not be used for a neck because with a neck its all about strength. The strings will generate a good amount of shear force, therefore the neck wood should have as little run out as possible.

Mahogany or Cedar

Mahogany is more dense than Spanish cedar and generally a bit darker in color as seen on the right, but both carve equally well. The difference in density will have an effect on the sound of the instrument. I find that mahogany because of its weight generally produces an instrument with deeper basses. Spanish cedar on the other hand has more of an effect on the trebles and help make them very clear.

This makes selecting one or the other a trade-off to some degree. Meaning you are giving something up to get something else. In order to minimize the trade-off things can be done to the treatment and selection of the soundboard to compensate for this

Wood for Fingerboards

classical guitar fingerboardGuitar fingerboards are typically  made of Gaboon ebony. They are occasionally made of  rosewood. Higher end guitars tend to use ebony exclusively.

Ebony is very dense wood and has excellent wear resistance. Since the fingerboards are constantly being hammered on, and fingers sliding around on them, ebony is an excellent wood choice. It will hold up to this abuse very well over time. It has been used on all types of stringed instruments for hundreds of years.

Good ebony fingerboards are becoming harder and harder to find. Jet black quarter sawn pieces of ebony for fingerboards are rapidly becoming a thing of the past. Today if you can find a good quarter sawn piece you more than likely will have to settle for some streaks. If forced to choose I will always choose visual flaws over inferior cuts of wood. Some types of rosewood will also work for fingerboards as well.  Macassar ebony will also work but this wood can also be difficult to find in the thicknesses needed.

If given a choice of a bad piece of ebony and a really good piece of an alternative wood such as a rosewood or Macassar ebony  I will choose the good piece of alternative wood every time when it comes to fingerboards.